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  • 251.
    Schmidt, Peter Paul
    et al.
    Stockholms Universitet.
    Rova, Ulrika
    Katterle, Bettina
    Stockholms Universitet.
    Thelander, Lars
    Umeå universitet.
    Gräslund, Astrid
    Stockholms Universitet.
    Kinetic evidence that a radical transfer pathway in protein R2 of mouse ribonucleotide reductase is involved in generation of the tyrosyl free radical1998Inngår i: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 273, nr 34, s. 21463-21472Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Class I ribonucleotide reductases consist of two subunits, R1 and R2. The active site is located in R1; active R2 contains a diferric center and a tyrosyl free radical (Tyr()), both essential for enzymatic activity. The proposed mechanism for the enzymatic reaction includes the transport of a reducing equivalent, i.e. electron or hydrogen radical, across a 35-Å distance between Tyr() in R2 and the active site in R1, which are connected by a hydrogen-bonded chain of conserved, catalytically essential amino acid residues. Asp266 and Trp103 in mouse R2 are part of this radical transfer pathway. The diferric/Tyr() site in R2 is reconstituted spontaneously by mixing iron-free apoR2 with Fe(II) and O2. The reconstitution reaction requires the delivery of an external reducing equivalent to form the diferric/Tyr() site. Reconstitution kinetics were investigated in mouse apo-wild type R2 and the three mutants D266A, W103Y, and W103F by rapid freeze-quench electron paramagnetic resonance with ≤4 Fe(II)/R2 at various reaction temperatures. The kinetics of Tyr() formation in D266A and W103Y is on average 20 times slower than in wild type R2. More strikingly, Tyr() formation is completely suppressed in W103F. No change in the reconstitution kinetics was found starting from Fe(II)-preloaded proteins, which shows that the mutations do not affect the rate of iron binding. Our results are consistent with a reaction mechanism using Asp266 and Trp103 for delivery of the external reducing equivalent. Further, the results with W103F suggest that an intact hydrogen-bonded chain is crucial for the reaction, indicating that the external reducing equivalent is a H(). Finally, the formation of Tyr() is not the slowest step of the reaction as it is in Escherichia coli R2, consistent with a stronger interaction between Tyr() and the iron center in mouse R2. A new electron paramagnetic resonance visible intermediate named mouse X, strikingly similar to species X found in E. coli R2, was detected only in small amounts under certain conditions. We propose that it may be an intermediate in a side reaction leading to a diferric center without forming the neighboring Tyr().

  • 252.
    Schwartz, Albert M.
    et al.
    Michigan State University.
    Berglund, Kris
    Comparison of supersaturation profiles employed on lysozyme crystallization from a hanging drop2001Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 1, nr 1, s. 81-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fiber optic Raman spectroscopy combined with a partial least-squares regression model was used as a monitor of lysozyme concentration during crystallization in a hanging-drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. The use of fiber optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous solutions, results in a powerful, noninvasive probe of the changing environment within the solution. Monitoring the concentration changes of the lysozyme within the hanging drop permits a measurement of the level of supersaturation of the system and provides for the potential of dynamic control of the crystallization process. Previously, hanging-drop experiments have been monitored in real time. These experiments have given insight into the changing environment of the hanging drop as the lysozyme within the hanging drop concentrates and nucleates and as crystal growth continues. Upon alteration of the ionic strength of the reservoir, the number, size, and quality of the resultant crystals has been affected. This investigation compares the resultant supersaturation of the lysozyme crystallization within the hanging drop by employing various reservoir conditions. These conditions include a constant ionic strength reservoir, a step change in reservoir ionic strength, and a differential change in reservoir ionic strength.

  • 253.
    Schwartz, Albert M.
    et al.
    University of Michigan.
    Berglund, Kris
    In situ monitoring and control of lysozyme concentration during crystallization in a hanging drop2000Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 210, nr 4, s. 753-760Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fiber optic Raman spectroscopy combined with a partial least-squares regression model was demonstrated as a monitor of lysozyme concentration during crystallization in a hanging drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. The use of fiber optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous solutions, results in a powerful noninvasive probe of the changing environment within the solution. Lysozyme concentrations were monitored in experiments at a constant reservoir ionic strength. Data from these uncontrolled experiments were used to determine rates of supersaturation, induction times, and the number and size of the resultant lysozyme crystals. Control experiments were performed by introducing step changes in the reservoir ionic strength. The step changes were initiated by comparing in situ rates of supersaturation with the rates of supersaturation calculated from the uncontrolled data. Monitoring the concentration changes of the lysozyme within the hanging drop permits a measurement of the level of supersaturation of the system and enhances the possibility of dynamic control of the crystallization process.

  • 254.
    Schwartz, A.M.
    et al.
    Michigan State University.
    Berglund, Kris
    Use of Raman spectroscopy for in situ monitoring of lysozyme concentration during crystallization in a hanging drop1999Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 203, nr 4, s. 599-603Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fiber optic Raman spectroscopy combined with a partial least-squares regression model was investigated as a means to monitor lysozyme concentration during crystallization in a hanging drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. This model was used to calculate the compositional changes within the hanging drop. The use of fibre optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous media, results in a powerful noninvasive probe of the changing environment within the solution. These preliminary findings indicate that solubility as well as supersaturation measurements can be made.

  • 255.
    Schwede, Sebastian
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Thorin, Eva
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Lindmark, Johan
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Klintenberg, Patrik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Jääskelainen, A
    Savonia Univ Appl Sci, Environm Engn, Kuopio, Finland.
    Suhonen, A.
    Savonia Univ Appl Sci, Environm Engn, Kuopio, Finland.
    Laatikainen, R.
    Univ Eastern Finland, Sch Pharm, Kuopio, Finland.
    Hakalehto, E.
    Univ Eastern Finland, Sch Pharm, Kuopio, Finland.
    Using slaughterhouse waste in a biochemical-based biorefinery – results from pilot scale tests2017Inngår i: Environmental technology, ISSN 0959-3330, E-ISSN 1479-487X, s. 1275-1284Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel biorefinery concept was piloted using protein-rich slaughterhouse waste, chicken manureand straw as feedstocks. The basic idea was to provide a proof of concept for the production ofplatform chemicals and biofuels from organic waste materials at non-septic conditions. Thedesired biochemical routes were 2,3-butanediol and acetone–butanol fermentation. The resultsshowed that hydrolysis resulted only in low amounts of easily degradable carbohydrates.However, amino acids released from the protein-rich slaughterhouse waste were utilized andfermented by the bacteria in the process. Product formation was directed towards acidogeniccompounds rather than solventogenic products due to increasing pH-value affected by ammoniarelease during amino acid fermentation. Hence, the process was not effective for 2,3-butanediolproduction, whereas butyrate, propionate,γ-aminobutyrate and valerate were predominantlyproduced. This offered fast means for converting tedious protein-rich waste mixtures intoutilizable chemical goods. Furthermore, the residual liquid from the bioreactor showedsignificantly higher biogas production potential than the corresponding substrates. Thecombination of the biorefinery approach to produce chemicals and biofuels with anaerobicdigestion of the residues to recover energy in form of methane and nutrients that can beutilized for animal feed production could be a feasible concept for organic waste utilization.

  • 256.
    Scott, Felipe
    et al.
    School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso.
    Li, Muyang
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Williams, Daniel L.
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Conejeros, Raúl
    School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Aroca, German
    School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso.
    Corn stover semi-mechanistic enzymatic hydrolysis model with tight parameter confidence intervals for model-based process design and optimization2015Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 177, s. 255-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Uncertainty associated to the estimated values of the parameters in a model is a key piece of information for decision makers and model users. However, this information is typically not reported or the confidence intervals are too large to be useful. A semi-mechanistic model for the enzymatic saccharification of dilute acid pretreated corn stover is proposed in this work, the model is a modification of an existing one providing a statistically significant improved fit towards a set of experimental data that includes varying initial solid loadings (10 to 25 % w/w) and the use of the pretreatment liquor and washed solids with or without supplementation of key inhibitors. A subset of 8 out of 17 parameters was identified, showing sufficiently tight confidence intervals to be used in uncertainty propagation and model analysis, without requiring interval truncation via expert judgment.

  • 257.
    Severin, Kathryn G.
    et al.
    Michigan State University.
    Ledford, Jeffrey S.
    Michigan State University.
    Torgerson, Beatrice A.
    Michigan State University.
    Berglund, Kris
    Characterization of titanium and zirconium valerate sol-gel films1994Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 6, nr 7, s. 890-898Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    FTIR and XPS have been used to characterize titanium and zirconium valerate thin films prepared using sol-gel techniques. Films were prepared by hydrolysis of titanium(IV) isopropoxide or zirconium(IV) n-propoxide in excess valeric acid at room temperature. Film solution chemistry, from precursors to cast films, was followed with FTIR. The structure and chemical composition of films spin cast from fresh and day-old solutions were determined. Results of these studies suggest that all films consist of a metal-oxygen polymer backbone coordinated with bidentate valerate ligands. No evidence for the presence of alkoxide ligands has been found. A small amount of water is present in all cast films. While solution aging experiments indicate that the zirconium film structure does not change with solution reaction time, carboxylate ligand concentrations are higher in titanium films made from aged solutions. Titanium films made from aged solutions contain slightly less than 1.5 valerate ligands/titanium atom. Zirconium films are more highly carboxylated with almost two valerate groups per metal center.

  • 258.
    Shanks, B. H.
    et al.
    Iowa State University.
    Berglund, Kris
    Contact nucleation from aqueous sucrose solutions1985Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 31, nr 1, s. 152-154Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Both initial size and growth rate distributions are observed for contact nuclei of sucrose. Results presented indicate sucrose contact nuclei appear to grow at a size independent rate and that the proper method of analysis of the growth rate dispersion present is the 'constant crystal growth' (CCG) model. Curvature in semilogarithmic population density-size plots from continuous sucrose crystallization studies is probably due to growth rate dispersion and not size dependent growth.

  • 259.
    Shiau, L. D.
    et al.
    Michigan State University.
    Berglund, Kris
    Growth kinetics of fructose crystals formed by contact nucleation1987Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 33, nr 6, s. 1028-1033Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite the large number of recent secondary nucleation and growth rate studies with the sucrose-water system, few data are available on the fructose-water system. Fructose is much more soluble in water than sucrose. Since fructose is a monosaccharide constituting half of the sucrose molecule, it is reasonable to consider that similar phenomena may exist with respect to nucleation and growth in the two systems. It is the objective of this work to perform photomicroscopic experiments on the fructose-water system to study these nucleation and growth characteristics.

  • 260.
    Shiau, L-D
    et al.
    Michigan State University.
    Berglund, Kris
    Model for a cascade crystallizer in the presence of growth rate dispersion1987Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 26, nr 12, s. 2515-2521Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model is developed based on the population balance to relate the resulting crystal size distribution (CSD) from a cascade of mixed suspension, mixed product removal (MSMPR) crystallizers to the growth rate distributions of each stage. This model employs the constant crystal growth (CCG) model, in which it is assumed that an individual crystal has an inherent, constant growth rate, but different crystals might have different inherent growth rates. An explicit recursion formula between the first three moments of the resulting crystal size distribution and the first three moments of growth rate distributions of each stage is presented for a N-stage MSMPR crystallizer. A computer program has been developed to predict the CSD from a three-stage MSMPR crystallizer with continuous seeding into the first stage and growth in the subsequent stages. The model is solved simultaneously with the mass balance by using power law growth kinetics. The CSD in each stage is assumed as a gamma distribution to compute the mean crystal size, production rate, and coefficient of variance.

  • 261.
    Shiau, Lie-Ding
    et al.
    Michigan State University.
    Berglund, Kris
    Growth rate dispersion in batch crystallization1990Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 36, nr 11, s. 1669-1679Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method for describing the crystal size distribution of a batch crystallizer in the presence of growth rate dispersion is presented. The analysis is based on the assumption that individual crystals have inherent constant growth rates, but the growth rate may vary from crystal to crystal, resulting in a distribution of growth rates. The method requires the availability of growth rate, growth rate dispersion, and nucleation rate expressions for prediction of the crystal size distribution. These required rate expressions can be recovered by the use of simple linear regressions from the CSD moment data. Prediction of the unsteady-state CSD was demonstrated using rate expressions for the sucrose-water system. Batch fructose experiments were analyzed to demonstrate the recovery of the growth and nucleation rates from the size distribution data.

  • 262.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mucin-like fusion proteins produced in Pichia pastoris as enhancers of immunogenecity of recombinant vaccines2011Doktoravhandling, med artikler (Annet vitenskapelig)
  • 263.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Pichia pastoris as a platform for the production of therapeutic glycoproteins2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Recombinant protein therapeutics is a growing market within the human medical biotechnology industry. The majority of all approved biopharmaceuticals are protein based and includes for example blood factors, anticoagulants, hormones, vaccine and monoclonal antibodies. Some of these protein based drugs are glycoproteins which require special carbohydrate structures attached to certain amino acids for correct folding, biological activity and/or stability in the circulation. The biosynthesis and covalent attachment of these oligosaccharides to the polypeptide core, the glycosyaltion, is species and tissue specific. Eukaryotic cells can attach the glycoproteins either to the side chain of aspargine (N-linked) or through the side chains of threonine or serine (O- linked). Controlling the synthesis of these carbohydrate structures, the glycosylation, is of prime concern when developing therapeutic glycoproteins and today mammalian cell culture systems are the preferred systems due to their ability to perform human-like glycosylation. However, mammalian systems are often hampered by disadvantages such as long production times, low protein titres, product heterogeneity and viral containment issues. These factors complicate large scale production of therapeutic glycoproteins and consequently there is a continual search for alternative expression systems with improved performance. The methylotrophic yeast Pichia pastoris (P. pastoris) has a number of attractive characteristics for heterologous protein production, including the ability to perform post-translational modifications, such as N- and O- linked glycosylation, and secrete large amounts of recombinant protein. Recombinant protein antigens glycosylated by P. pastoris have shown enhanced immunogenicity compared to their non-glycosylated counterparts. The high mannose content of yeast derived N- and O-glycans is proposed to target the recombinant antigens to immunoregulatory, mannose specific receptors which upon binding promotes the enhanced immune responses. These findings suggest P. pastoris as a platform for production of recombinant vaccines. However, structural and functional characterizations of the glycans involved are poor, specifically for O-glycans. PSGL-1/mIgG2b, is a chimeric mucin-like protein with the potential to carry 106 O-glycans and six N-glycans, and AGP-1/mIgG2b is a chimeric protein with the potential to carry twelve N-glycans. In the context of mannose specific receptor targeted vaccines, glycoproteins with this type of glycosylation expressed by P. pastoris have not been studied before. The objective of this study was to develop bioprocesses for efficient production of PSGL-1/mIgG2b and AGP-1/mIgG2b The main purpose of this was to supply enough material for characterisation and functional studies of PSGL-1/mIgG2b and AGP-1/mIgG2b in the context of binding three mannose specific receptors, MR, DC-SIGN and MBL, but also to identify important bioprocess parameters for large scale production of the recombinant glycoproteins. Methanol feed, pH and certain media components were found to be critical for productivity and homogeneity of the recombinant proteins. During the course of this study a bioprocess which improved productivity from 10 mg/L to around 200 mg/L for PSGL- 1/mIgG2b and from 3.5 mg/L to 21 mg/L for AGP-1/mIgG2b along with significantly reduced proteolytic activity was developed. To relate a certain glycan structure with biological activity, characterization of the PSGL-1/mIgG2b O-glycans in combination with binding studies to the recombinant mannose specific receptors MR, DC-SIGN and MBL was conducted. Biacore analysis revealed high affinity binding of both PSGL-1/mIgG2b and AGP-1/mIgG2b to all receptors. MS of O-glycans released from PSGL-1/mIgG2b indicated Hex2-9 structures. For fast, on-line optimization of recombinant protein production an optimization system based on the intrinsic fluorescence of the green fluorescent protein (GFP) was developed. Recombinant strains of P. pastoris secreting the GFP fusion protein PSGL-1/mIgG2b/GFP were generated and the fluorescence system was applied to follow on-line fluorescence under various induction conditions. Subsequently, P. pastoris secreting PSGL- 1/mIgG2b was induced under the same conditions. Correlations between the on- line fluorescence and the secreted amount of PSGL-1/mIgG2b were investigated. It was concluded that the on-line system had the potential to reflect the translational rate of PSGL-1/mIgG2b/GFP. However, due to different secretion properties of PSGL-1/mIgG2b/GFP and PSGL-1/mIgG2b in combination with potential genetic instability no correlations were found. The system may still have a value for recombinant proteins expressed intracellularly.

  • 264.
    Sjöblom, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gustafsson, Anki
    Recopharma AB.
    Strindelius, Lena
    Recopharma AB.
    Johansson, Tomas
    Recopharma AB.
    Björnström, Linda
    Absorber AB, Stockholm.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holgersson, Jan
    Karolinska Institutet.
    O-glycan variability of glycoproteins expressed by Pichia pastoris and its effects on mannose receptor binding properties2008Inngår i: Journal of Biotechnology, ISSN 0168-1656, E-ISSN 1873-4863, Vol. 136, nr Suppl. 1, s. S516-Artikkel i tidsskrift (Annet vitenskapelig)
  • 265.
    Sjöblom, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Lindberg, Linda
    Absorber AB, Stockholm.
    Holgersson, Jan
    Sahlgrenska akademin, Göteborg.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Secretion and expression dynamics of a GFP-tagged mucin-type fusion protein in high cell density Pichia pastoris bioreactor cultivations2012Inngår i: Advances in Bioscience and Biotechnology, ISSN 2156-8456, E-ISSN 2156-8502, Vol. 3, nr 3, s. 238-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The methanol inducible alcohol oxidase 1 promoter and the Saccharomyces cerevisiae alpha-factor prepro secretion signal were used to drive expression and secretion of a mucin-type fusion protein by Pichia pastoris in 1 L scale bioreactors. The aim of the study was to understand how varying expression rates influenced the secretion dynamics of the fusion protein in terms of intracellular- and extracellular concentrations. Endoplasmic reticulum (ER) folding stress was assessed by the relative expression of the unfolded protein response controlled KAR2 gene. Three predefined methanol feeding models were applied to control the fusion protein synthesis rate. To track the fusion protein synthesis in a non-invasive manner and to follow its intracellular distribution, its C-terminal was linked to the green fluorescent protein. Under all conditions the fusion protein was found to partially accumulate intracellularly, where the major fraction was an insoluble, fluorescent full-sized protein. The high degree of glycosylation of the insoluble fusion protein indicated a secretory bottle-neck in the Golgi-system. This result was consistent with low ER folding stress as quantified by the relative expression of the KAR2 gene. Reduction of recombinant protein synthesis rate, by using lower feed rates of methanol, enhanced extracellular concentrations from 8 to 18 mg·L–1 and reduced the rate of intracellular accumulation. This clearly demonstrates the importance of tuning the synthesis rate with secretory bottle-necks to maintain secretion.

  • 266.
    Sjöblom, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Catalytic upgrading of butyric acid towards fine chemicals and biofuels2016Inngår i: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 363, nr 8, artikkel-id fnw064Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fermentation based production of butyric acid is robust and efficient. Modern catalytic technologies make it possible to convert butyric acid to important fine chemicals and biofuels. Here current chemocatalytic and biocatalytic conversion methods are reviewed with a focus on upgrading butyric acid to 1-butanol or butyl-butyrate. Supported Ruthenium and Platinum based catalyst and lipase exhibit important activities which can pave the way for more sustainable process concepts for the production of green fuels and chemicals.

  • 267.
    Sjöblom, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Production of butyric acid by Clostridium tyrobutyricum (ATCC25755) using sweet sorghum stalks and beet molasses2015Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 74, s. 535-544Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Enzymatically liquefied sweet sorghum stalks and beet molasses were evaluated for butyrate production using Clostridium tyrobutyricum in 1 L scale fed-batch fermentations. The hydrolysates used for the fermentations were prepared separately by liquefying the sorghum stalks at 50 °C, pH 5.0 for 18 h, with 30% (w/v) DM content using the enzyme preparation Cellic® CTec2 at an activity of 26.5 FPU/g DM. To enhance sucrose consumption, the fermentations were supplemented with invertase at an activity equivalent to 8.3 U/g DM. With the hydrolysate as the feedstock, a butyrate concentration of 37.2 ± 0.8 g/L, a productivity of 0.86 ± 0.02 g/L h and a yield of 0.39 ± 0.02 g/g (p = 0.05) consumed sugars were obtained. Finally, a butyrate concentration of 58.8 g/L, a productivity of 1.9 g/L h, a butyrate yield of 0.52 g/g consumed sugars and a dry cell mass concentration of 15.7 g/L were obtained with fed-batch cultivation and a constant feed consisting of 64% sorghum hydrolysate juice and 36% molasses. Evidence for inducible saccharolytic activity was also proven, as the cellulase activity in the culture supernatant was found more than double during feed with limiting sugar concentrations. The present study clearly demonstrates that combinations of low cost raw materials can be used for efficient butyrate production, also without cell immobilization.

  • 268.
    Sjöblom, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Matsakas, Leonidas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Krige, Adolf
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Direct electricity generation from sweet sorghum stalks and anaerobic sludge2017Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 108, s. 505-511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dried sweet sorghum stalks were valorized as a raw material for electricity generation in a two chamber microbial fuel cell using anaerobic sludge from a biogas plant as inoculum. The maximum voltage obtained on the sorghum stalks at an operating temperature of 35 °C was 546 mV with a maximum power- and current density of 131 mW/m2 and 543 mA/m2, respectively. The coulombic efficiency was 2.2%. Polarization data indicated that Ohmic resistances were dominant with an internal resistance of 182 Ω. The total electrical energy per gram of dried sorghum stalks was 165 J/g. Enzymatic treatment of the sorghum stalks did not improve the total electrical energy obtained. A metabolic study demonstrated that the sugars were quickly fermented to formate, acetate, propionate, lactate and butyrate with acetate and butyrate being the dominant acids during electricity generation

  • 269.
    Sjöblom, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Risberg, Per
    Internal Combustion Engines, Department of Machine Design, Royal Institute of Technology, Stockholm..
    Filippova, Alfia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Öhrman, Olov G W
    RISE Energy Technology Center, Piteå.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    In Situ Biocatalytic Synthesis of Butyl Butyrate in Diesel and Engine Evaluations2017Inngår i: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 9, nr 24, s. 4529-4537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Blending petroleum fuels with biofuels is likely to become increasingly important over the years to come. Butyl butyrate has promising characteristics as a blend component in diesel and can be synthesized by lipase-catalyzed esterification of 1-butanol and butyric acid, which both can be derived from fermentation technologies. In the current study, the enzyme load and reaction temperature were optimized for the production of butyl butyrate with Novozyme435 (immobilized Candida antarctica lipaseB) directly in diesel at a substrate concentration of 1m using a molar ratio of 1:1 between n-butanol and butyric acid. Optimum conditions were found by using a central composite design at an enzyme load of 12% of substrate weight and a temperature of 57°C, giving 90% yield conversion in 30min, corresponding to a butyl butyrate productivity of 1.8molL-1h-1. Diesel blended with 5, 10, and 30% butyl butyrate was tested in a heavy-duty diesel engine under two load cases. The ignition properties of the blended fuels were very similar to pure diesel, making butyl butyrate an interesting diesel substitute. The emission analysis demonstrated lower soot and CO emissions, similar hydrocarbons levels and slightly increased NOx levels compared with using pure diesel. The high activity of lipase in diesel and the compatibility between diesel and butyl butyrate opens up the possibility to develop fuel blending systems where the synthesis of the blend-in component occurs directly in the fuel.

  • 270.
    Skogsberg, Zara
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teknisk biologi. Linköpings universitet, Tekniska högskolan.
    Investigation of the Impact on Yeast Fermentation Performance in Production of Pale Lager Beer through Management Control2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Through a full factorial design experiment, the effects of time between worts, wort aeration and yeast dosage in production of a pale lager beer were examined in the beer process at Spendrups Bryggeri AB. The aim was to learn how different parameters may affect the yeast fermentation performance during beer production. Response variables used were the concentrations of ethyl acetate and isoamyl acetate, free amino nitrogen (FAN) degradation and change in extract. A statistical analysis showed that the concentration of ethyl acetate is dependent on yeast dosage and the interaction between time between worts and aeration while the isoamyl acetate concentration is dependent on yeast dosage and time between worts. No parameters are statistically significant for FAN degradation while the change in extract is dependent on the yeast dosage. Due to botched runs, mostly because of aeration problems, it was not possible to verify theoretical parameter values and responses. Since the aeration was not properly performed, the management of the aeration control should be further investigated. Ester analysis and analysis of FAN were performed as worts entered and exited horizontal fermentation tanks. An additional analysis of ester content was also performed as the early stage beer was transferred into lagering tanks. Cell viability as well as extract, pH and tank temperature was measured daily to verify the state of fermentation. Statistical calculations showed that when using NucleoCounter YC-100, there is no significant difference between analysis made of samples homogenized by a magnetic stirrer and samples shaken by hand.

  • 271.
    Skvaril, Jan
    et al.
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Kyprianidis, Konstantinos
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Dahlquist, Erik
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Applications of near-infrared spectroscopy (NIRS) in biomass energy conversion processes: A review2017Inngår i: Applied spectroscopy reviews (Softcover ed.), ISSN 0570-4928, E-ISSN 1520-569X, Vol. 52, nr 8, s. 675-728Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biomass used in energy conversion processes is typically characterized by high variability, making its utilization challenging. Therefore, there is a need for a fast and non-destructive method to determine feedstock/product properties and directly monitor process reactors. The near-infrared spectroscopy (NIRS) technique together with advanced data analysis methods offers a possible solution. This review focuses on the introduction of the NIRS method and its recent applications to physical, thermochemical, biochemical and physiochemical biomass conversion processes represented mainly by pelleting, combustion, gasification, pyrolysis, as well as biogas, bioethanol, and biodiesel production. NIRS has been proven to be a reliable and inexpensive method with a great potential for use in process optimization, advanced control, or product quality assurance.

  • 272.
    Srivastava, Vaibhav
    et al.
    Division of Glycoscience, School of Biotechnology, Royal Institute of Technology.
    Obudulu, Ogonna
    Computational Life Science Cluster (CLiC), Department of Chemistry, Umeå.
    Löfstedt, Tommy
    Department of Chemistry, Umeå University.
    Rydén, Patrik
    Umeå University, Department of Mathematics and Mathematical Statistics.
    Nilsson, Robert
    Ahnlund, Maria
    Umeå Plant Science Centre, Department of Forest Genetics and Plant.
    Johansson, Annika
    Umeå Plant Science Centre, Department of Forest Genetics and Plant.
    Jonsson, Pär
    Department of Chemistry, Umeå University.
    Freyhult, Eva
    Computational Life Science Cluster (CLiC), Department of Chemistry, Umeå.
    Qvarnström, Johanna
    Umeå Plant Science Centre, Department of Forest Genetics and Plant.
    Karlsson, Jan
    Umeå Plant Science Centre, Department of Plant Physiology, Umeå University.
    Melzer, Michael
    Department of Molecular Cell Biology, Institute of Plant Genetics and Crop Plant Research, Gatersleben.
    Moritz, Thomas
    Umeå Plant Science Centre, Department of Forest Genetics and Plant.
    Trygg, Johan
    Computational Life Science Cluster (CLiC), Department of Chemistry, Umeå.
    Hvidsten, Torgeir R
    Department of Chemistry, Biotechnology and Food Science, Norwegian, University of Life Sciences, 1432 Ås.
    Wingsle, Gunnar
    Umeå Plant Science Centre, Department of Forest Genetics and Plant.
    OnPLS integration of transcriptomic, proteomic and metabolomic data shows multi-level oxidative stress responses in the cambium of transgenic hipI- superoxide dismutase Populus plants2013Inngår i: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 14, nr 893Artikkel i tidsskrift (Fagfellevurdert)
  • 273.
    Stenberg, Anna
    et al.
    Luleå tekniska universitet.
    Malinovskiy, Dmitry
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Andren, Henrik
    Forsling, Willis
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Engström, Lena-Maria
    Umeå universitet.
    Wahlin, Anders
    Umeå universitet.
    Engström, Emma
    Rodushkin, Ilya
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Baxter, Douglas
    Measurement of iron and zinc isotopes in human whole blood: preliminary application to the study of HFE genotypes2005Inngår i: Journal of Trace Elements in Medicine and Biology, ISSN 0946-672X, E-ISSN 1878-3252, Vol. 19, nr 1, s. 55-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multi-collector inductively coupled plasma - sector field mass spectrometry was applied to the measurement of Fe and Zn isotopes in human whole blood samples. For the Fe present in the blood of healthy adults, enrichment of the lighter isotopes relative to a standard material was observed, in agreement with earlier studies. The level of fractionation was found to be lower in hemochromatosis patients exhibiting homozygous (C282Y/C282Y) mutation of the HFE gene. On the one hand, this reinforces the hypothesis that Fe fractionation in blood decreases with enhanced dietary absorption. On the other hand, this contradicts predictions made on the basis of determinations of Fe fractionation in blood samples collected from subjects characterized by milder HFE mutations. In healthy subjects, the Zn in blood is depleted in lighter isotopes, consistent with the limited number of prior observations. As for Fe, the Zn isotopic composition exhibited a tendency toward lower levels of fractionation in the blood of subjects with hereditary hemochromatosis with homozygous mutation (C282Y/C282Y) of the HFE gene. The results therefore suggest that both Fe and Zn isotopic signatures in whole blood, at least to some extent, reflect polymorphisms in the HFE gene.

  • 274.
    Stephanidis, S.D.
    et al.
    Chemical Process Engineering Research Institute, CERTH.
    Nitsos, Christos
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Kalogiannis, Konstantions G.
    Chemical Process Engineering Research Institute, CERTH.
    Iliopoulou, Eleni F.
    Chemical Process Engineering Research Institute, CERTH.
    Lappas, Angelos A
    Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece, Chemical Process Engineering Research Institute, CERTH.
    Triantafyllidis, Kostas
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece.
    Catalytic upgrading of lignocellulosic biomass pyrolysis vapours: Effect of hydrothermal pre-treatment of biomass2011Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 167, nr 1, s. 37-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main objective of the present work was the study of the effect of hydrothermal pretreatment of lignocellulosic biomass (beech wood) on the product yields and bio-oil composition produced from biomass flash pyrolysis as well as from the catalytic upgrading of the biomass pyrolysis vapours. The hydrothermal pretreatment of lignocellulosic biomass was performed at a severity factor (Ro) of 3.55 leading to ∼35 wt.% loss of solids, mainly due to solubilization and removal of hemicellulose. The production of sugars (mainly levoglucosan) was significantly increased by the use of the hydrothermally pretreated biomass instead of the untreated biomass in the non-catalytic flash pyrolysis experiments. On the other hand, the concentration of carboxylic acids, ketones and phenols was decreased in the bio-oil derived from the pretreated biomass. The catalysts tested in the upgrading of the biomass pyrolysis vapours were the strongly acidic zeolites H-ZSM-5 and silicalite (with very low number of acid sites) and the mildly acidic mesoporous aluminosilicate Al-MCM-41. The effect of catalysts on product yields and composition of bio-oil in the upgrading of pyrolysis vapours, was similar for both the pretreated and untreated biomass. The use of zeolite H-ZSM-5 decreased the total liquid yield (bio-oil) via decreasing the organic phase of bio-oil and increasing its water content, accompanied by increase of gases and moderate formation of coke on the catalyst. The zeolite silicalite and the Al-MCM-41 induced similar effects with those of H-ZSM-5 but to a less extent, except of the significantly higher coke that was deposited on Al-MCM-41. With regard to the composition of the bio-oil, all the catalysts and mostly the strongly acidic H-ZSM-5 zeolite reduced the oxygen content of the organic fraction, mainly by decreasing the concentration of acids, ketones and phenols in the untreated biomass pyrolysis oil or the concentration of sugars in the pretreated biomass pyrolysis oil. Aromatics and polycyclic aromatic hydrocarbons (PAHs) were significantly increased by the use of all catalysts, for both types of biomass feed. A substantial increase in the concentration of phenols was observed in the upgraded bio-oil derived by the hydrothermally pretreated biomass, using the less acidic silicalite and Al-MCM-41 catalysts

  • 275.
    Stoklosa, Ryan J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    del Pilar Orjuela, Andrea
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    da Costa Sousa, Leonardo
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Uppugundla, Nirmal
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Williams, Daniel L.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Dale, Bruce E.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Balan, Venkatesh
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Techno-economic comparison of centralized versus decentralized biorefineries for two alkaline pretreatment processes2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 226, s. 9-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, corn stover subjected to ammonia fiber expansion (AFEX™) pretreatment or alkaline pre-extraction followed by hydrogen peroxide post-treatment (AHP pretreatment) were compared for their enzymatic hydrolysis yields over a range of solids loadings, enzymes loadings, and enzyme combinations. Process techno-economic models were compared for cellulosic ethanol production for a biorefinery that handles 2000 tons per day of corn stover employing a centralized biorefinery approach with AHP or a de-centralized AFEX pretreatment followed by biomass densification feeding a centralized biorefinery. A techno-economic analysis (TEA) of these scenarios shows that the AFEX process resulted in the highest capital investment but also has the lowest minimum ethanol selling price (MESP) at $2.09/gal, primarily due to good energy integration and an efficient ammonia recovery system. The economics of AHP could be made more competitive if oxidant loadings were reduced and the alkali and sugar losses were also decreased.

  • 276.
    Stoklosa, Ryan J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Fractionation and Improved Enzymatic Deconstruction of Hardwoods with Alkaline Delignification2015Inngår i: Bioenergy Research, ISSN 1939-1234, E-ISSN 1939-1242, Vol. 8, nr 3, s. 1224-1234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, an alkaline delignification was investigated for several industrially relevant hardwoods to understand the kinetics of xylan solubilization and degradation and the role of residual lignin content in setting cell wall recalcitrance to enzymatic hydrolysis. Between 34 and 50 % of the xylan was solubilized during the heat-up stage of the pretreatment and undergoes degradation, depolymerization, as well as substantial disappearance of the glucuronic acid substitutions on the xylan during the bulk delignification phase. An important finding is that substantial xylan is still present in the liquor without degradation. Cellulose hydrolysis yields in the range of 80 to 90 % were achievable within 24–48 h for the diverse hardwoods subjected to delignification by alkali at modest enzyme loadings. It was found that substantial delignification was not necessary to achieve these high hydrolysis yields and that hybrid poplar subjected to pretreatment removing only 46 % of the lignin was capable of reaching yields comparable to hybrid poplar pretreated to 67 or 86 % lignin removal. Decreasing the lignin content was found to increase the initial rate of cellulose hydrolysis to glucose while lignin contents under approximately 70 mg/g original biomass were found to slightly decrease the maximum extent of hydrolysis, presumably due to drying-induced cellulose aggregation and pore collapse. Pretreatments were performed on woodchips, which necessitated a “disintegration” step following pretreatment. This allowed the effect of comminution method to be investigated for the three hardwoods subjected to the highest level of delignification. It was found that additional knife-milling following distintegration did not impact either the rate or extent of glucan and xylan hydrolysis.

  • 277.
    Sunner, Hampus
    et al.
    Chalmers University of Technology, Department of Chemical and Biological Engineering, Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology.
    Charavgi, Maria-Despoina
    National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Olsson, Lisbeth
    Technical University of Denmark, Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Glucuronoyl Esterase Screening and Characterization Assays Utilizing Commercially Available Benzyl Glucuronic Acid Ester2015Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 20, nr 10, s. 17807-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Research on glucuronoyl esterases (GEs) has been hampered by the lack of enzyme assays based on easily obtainable substrates. While benzyl d-glucuronic acid ester (BnGlcA) is a commercially available substrate that can be used for GE assays, several considerations regarding substrate instability, limited solubility and low apparent affinities should be made. In this work we discuss the factors that are important when using BnGlcA for assaying GE activity and show how these can be applied when designing BnGlcA-based GE assays for different applications: a thin-layer chromatography assay for qualitative activity detection, a coupled-enzyme spectrophotometric assay that can be used for high-throughput screening or general activity determinations and a HPLC-based detection method allowing kinetic determinations. The three-level experimental procedure not merely facilitates routine, fast and simple biochemical characterizations but it can also give rise to the discovery of different GEs through an extensive screening of heterologous Genomic and Metagenomic expression libraries.

  • 278.
    Tamagawa, Rosana E.
    et al.
    Campinas State University.
    Miranda, Everson A.
    Campinas State University.
    Berglund, Kris
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Simultaneous monitoring of protein and (NH4)(2)SO4 concentrations in aprotinin hanging-drop crystallization using Raman spectroscopy2002Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 2, nr 6, s. 511-514Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study the use of fiber optic Raman spectroscopy for the in situ monitoring of aprotinin supersaturation in a hanging-drop crystallization is described. The crystallizing agent, (NH4)2SO4, is Raman active, which allows monitoring of the salt concentration in the drop during the whole hanging-drop crystallization process in addition to monitoring of the aprotinin concentration. Through the continuous measuring of protein and salt concentrations, supersaturation in the drop solution was measured in real time. Moreover, through the monitoring of protein and salt concentrations, the cocrystallization of aprotinin and (NH4)2SO4 was observed.

  • 279.
    Tamagawa, Rosana
    et al.
    Campinas State University.
    Miranda, Everson
    Michigan State University.
    Berglund, Kris
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Raman spectroscopic monitoring and control of aprotinin supersaturation in hanging-drop crystallization2002Inngår i: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 2, nr 4, s. 263-267Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fiber optic Raman spectroscopy is used for in situ monitoring of supersaturation during the hanging-drop crystallization of aprotinin. Schwartz and Berglund (1999) previously demonstrated this technique for lysozyme crystallization and showed it combines two critical elements for protein crystallization studies: real-time monitoring/control of supersaturation and small amounts of sample. Experiments were carried out using 10 L of protein solution. A partial-least-squares (PLS) calibration based on Raman spectra of standard solutions allowed an accurate measurement of aprotinin in a range of 2-100 mg/mL with a standard error of 0.54 mg/mL determined by a leave-one-out cross validation. A 10× microscope attached to a Raman fiber optic probe allowed the monitoring of the hanging-drop liquid phase in a noninvasive and real-time mode. Aprotinin solubility determined by measuring the protein concentration of drop solution at equilibrium decreased with increase in NaCl concentration. By continuously collecting Raman spectra of the liquid phase in the drop, the protein concentration was monitored in real time during the whole process. Control of supersaturation by manipulating the evaporation rate of the drop solution allowed the optimization of the process, leading to an increase in the resulting crystal size.

  • 280.
    Thörn, Christian
    et al.
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Utadha, D.B.R.K. Gupta
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Zhou, Hao
    Department of Environmental Science and Technology, Dalian University of Technology.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Topakas, Evangelos
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Olsson, Lisbeth
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Understanding the pH-dependent immobilization efficacy of feruloyl esterase-C on mesoporous silica and its structure-activity changes2013Inngår i: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 93, s. 65-72Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of the present investigation was to study the pH dependence of both the immobilization process and the enzyme activity of a feruloyl esterase (FoFaeC from Fusarium oxysporum) immobilized in mesoporous silica. This was done by interpreting experimental results with theoretical molecular modeling of the enzyme structure. Modeling of the 3D structure of the enzyme together with calculations of the electrostatic surface potential showed that changes in the electrostatic potential of the protein surface were correlated with the pH dependence of the immobilization process. High immobilization yields were associated with an increase in pH. The transesterification activity of both immobilized and free enzyme was studied at different values of pH and the optimal pH of the immobilized enzyme was found to be one unit lower than that for the free enzyme. The surface charge distribution around the binding pocket was identified as being a crucial factor for the accessibility of the active site of the immobilized enzyme, indicating that the orientation of the enzyme inside the pores is pH dependent. Interestingly, it was observed that the immobilization pH affects the specific activity, irrespective of the changes in reaction pH. This was identified as a pH memory effect for the immobilized enzyme. On the other hand, a change in product selectivity of the immobilized enzyme was also observed when the transesterification reaction was run in MOPS buffer instead of citrate phosphate buffer. Molecular docking studies revealed that the MOPS buffer molecule can bind to the enzyme binding pocket, and can therefore be assumed to modulate the product selectivity of the immobilized enzyme towards transesterification.

  • 281.
    Tian, Bo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    de la Torre, Teresa Zardan Gomez
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Donolato, Marco
    Tech Univ Denmark, Dept Micro & Nanotechnol, DTU Nanotech, Bldg 345 East, DK-2800 Lyngby, Denmark..
    Hansen, Mikkel Fougt
    Tech Univ Denmark, Dept Micro & Nanotechnol, DTU Nanotech, Bldg 345 East, DK-2800 Lyngby, Denmark..
    Svedlindh, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Strömberg, Mattias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Multi-scale magnetic nanoparticle based optomagnetic bioassay for sensitive DNA and bacteria detection2016Inngår i: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 8, nr 25, s. 5009-5016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Benefiting from their rapid readout, highly flexible devices and low-cost portable systems, optomagnetic biosensors have drawn increased attention in recent years as bioassay technologies for small molecules, biomarkers, DNA, and bacteria. Herein, an optomagnetic bioassay strategy suitable for point-of-care diagnostics, utilizing functionalized magnetic nanoparticles (100 nm) with Brownian relaxation behavior is optimized in order to obtain higher detection sensitivity for DNA molecules and bacteria. Presence of target DNA sequences or bacteria changes the dynamic behavior of the magnetic nanoparticles (binding to the target) and thus the optomagnetic response of the sample, which is measured by an optomagnetic setup including a 405 nm laser and a photodetector. The limit of detection is mainly set by the lowest measurable concentration of magnetic nanoparticles. Herein, as new results compared to previous work, we systematically optimize the concentration of 100 nm magnetic nanoparticles to increase the assay sensitivity and lower the limit of detection. To enable biplex detection, we perform this optimization in the presence of larger 250 nm magnetic nanoparticles that do not interact with the target. We show that the optimization and lowering of the 100 nm magnetic nanoparticle concentration result in a limit of detection of 780 fM of DNA coils formed by rolling circle amplification (size of about 1 mu m) and 10(5) CFU per mL Salmonella (for immunoassay). These values are 15 times lower than those reported previously for this readout principle. Finally, we show that the 250 nm magnetic nanoparticles can serve as a second detection label for qualitative biplex detection of DNA coils formed by rolling circle amplification from V. cholerae and E. coli DNA coils using 100 nm and 250 nm magnetic detection nanoparticles, respectively.

  • 282.
    Tomek, Kyle J.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Saldarriaga, Carlos Rafael Castillo
    Department of Chemical and Environmental Engineering, Universidad Nacional de Colombia, Bogotá.
    Velasquez, Fernando Peregrino Cordoba
    Department of Chemical and Environmental Engineering, Universidad Nacional de Colombia, Bogotá.
    Liu, Tongjun
    DOE-Great Lakes Bioenergy Research Center, Michigan State University, East Lansing.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Whitehead, Timothy A.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Removal and upgrading of lignocellulosic fermentation inhibitors by in situ biocatalysis and liquid-liquid extraction2015Inngår i: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 112, nr 3, s. 627-632Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydroxycinnamic acids are known to inhibit microbial growth during fermentation of lignocellulosic biomass hydrolysates, and the ability to diminish hydroxycinnamic acid toxicity would allow for more effective biological conversion of biomass to fuels and other value-added products. In this work, we provide a proof-of-concept of an in situ approach to remove these fermentation inhibitors through constituent expression of a phenolic acid decarboxylase combined with liquid-liquid extraction of the vinyl phenol products. As a first step, we confirmed using simulated fermentation conditions in two model organisms, Escherichia coli and Saccharomyces cerevisiae, that the product 4-vinyl guaiacol is more inhibitory to growth than ferulic acid. Partition coefficients of ferulic acid, p-coumaric acid, 4-vinyl guaiacol, and 4-ethyl phenol were measured for long-chain primary alcohols and alkanes, and tetradecane was identified as a co-solvent that can preferentially extract vinyl phenols relative to the acid parent and additionally had no effect on microbial growth rates or ethanol yields. Finally, E. coli expressing an active phenolic acid decarboxylase retained near maximum anaerobic growth rates in the presence of ferulic acid if and only if tetradecane was added to the fermentation broth. This work confirms the feasibility of donating catabolic pathways into fermentative microorganisms in order to ameliorate the effects of hydroxycinnamic acids on growth rates, and suggests a general strategy of detoxification by simultaneous biological conversion and extraction.

  • 283. Topakas, E.
    et al.
    Panagiotou, G
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Characteristics, sources, production and applications. Xylanases2013Inngår i: Bioprocessing Technologies in Biorefinery for Sustainable Production of Fuels, Chemicals, and Polymers, John Wiley & Sons, 2013, s. 147-169Kapittel i bok, del av antologi (Fagfellevurdert)
  • 284.
    Topakas, Evangelos
    et al.
    Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Screening and purification of recombinant lignocellulolytic enzymes2014Inngår i: Protein Downstream Processing: Design, Development and Application of High and Low-Resolution Methods, New York: Humana Press, 2014, s. 517-526Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In the search for novel biomass-degrading enzymes through mining microbial genomes, it is necessary to apply functional tests during high-throughput screenings, which are capable of detecting enzymatic activities directly by way of plate assay. Using the most efficient expression systems of Escherichia coli and Pichia pastoris, the production of high amount of His-tagged recombinant proteins could be thrived, allowing the one-step isolation by affinity chromatography. Here, we describe simple and efficient assay techniques for the detection of various biomass-degrading enzymatic activities on agar plates, such as cellulolytic and hemicellulolytic activities and their isolation using immobilized-metal affinity chromatography.

  • 285.
    Topakas, Evangelos
    et al.
    School of Chemical Engineering, National Technical University of Athens.
    Moukouli, Maria
    School of Chemical Engineering, National Technical University of Athens.
    Dimarogona, Maria
    School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Expression, characterization and structural modelling of a feruloyl esterase from the thermophilic fungus Myceliophthora thermophila2012Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 94, nr 2, s. 399-411Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A ferulic acid esterase (FAE) from the thermophilic fungus Myceliophthora thermophila (synonym Sporotrichum thermophile), belonging to the carbohydrate esterase family 1 (CE-1), was functionally expressed in methylotrophic yeast Pichia pastoris. The putative FAE from the genomic DNA was successfully cloned in P. pastoris X-33 to confirm that the enzyme exhibits FAE activity. The recombinant FAE was purified to its homogeneity (39 kDa) and subsequently characterized using a series of model substrates including methyl esters of hydroxycinnamates, alkyl ferulates and monoferuloylated 4-nitrophenyl glycosides. The substrate specificity profiling reveals that the enzyme shows a preference for the hydrolysis of methyl caffeate and p-coumarate and a strong preference for the hydrolysis of n-butyl and iso-butyl ferulate. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 and C-2 linkages of arabinofuranose, whilst it was found capable of de-esterifying acetylated glucuronoxylans. Ferulic acid (FA) was efficiently released from destarched wheat bran when the esterase was incubated together with an M3 xylanase from Trichoderma longibrachiatum (a maximum of 41% total FA released after 1 h incubation). Prediction of the secondary structure of MtFae1a was performed in the PSIPRED server whilst modelling the 3D structure was accomplished by the use of the HH 3D structure prediction server.

  • 286.
    Uusi-Penttilä, Marketta
    et al.
    Michigan State University.
    Richards, Robert J.
    Michigan State University.
    Blowers, Paul
    Michigan State University.
    Torgerson, Béatrice A.
    Michigan State University.
    Berglund, Kris
    Liquid-liquid equilibria of selected dibasic ester + water + solvent ternary systems1996Inngår i: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 41, nr 2, s. 235-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental liquid-liquid equilibria for various dibasic ester + solvent + water systems were obtained at 297 K. These systems are suggested as possible substitutes in applications where chlorocarbons and aromatic hydrocarbons are used. The dibasic esters can also be used as novel solvents in separation techniques.

  • 287.
    Uusi-Penttilä, Marketta S
    et al.
    Michigan State University.
    Berglund, Kris
    Spectroscopic monitoring of environmentally benign anti-solvent crystallization1996Inngår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 166, nr 1-4, s. 967-970Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There are very few studies dealing with the fundamentals of anti-solvent crystallization, even though this crystallization method is widely used in the pharmaceutical industry. Anti-solvent crystallization is accomplished by adding a miscible anti-solvent into a mixture of solute and solvent, effectively reducing the solubility of the solute in the solvent, and thus, causing the crystallization of the solute. Unfortunately, many of the anti-solvents used today are chlorinated hydrocarbons suspected of environmental damage. The current research demonstrates the use of environmentally benign solvents for anti-solvent crystallization and new approaches for monitoring of the solvent behavior during an anti-solvent crystallization. Results are presented confirming the efficacy of various water and ester systems for anti-solvent crystallization. Furthermore, the application of fluorescence spectroscopy for monitoring these crystallizations is demonstrated.

  • 288.
    Uusi-Penttilä, Marketta S.
    et al.
    Michigan State University.
    Richards, Robert J.
    Michigan State University.
    Torgerson, Béatrice A.
    Michigan State University.
    Berglund, Kris
    Spectroscopically determined dielectric constants for various esters1997Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 36, nr 2, s. 510-512Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polarity of a solvent can be defined by the Onsager function or the Debye function, which both are functions of the static dielectric constant. Polarity has also been shown to be related to the solvatochromic shifts of the absorption and fluorescence spectra. In this study, the emission maxima of the probe molecule Nile Red were taken in different solvents of known dielectric constants, and relationships between the emission maxima and the Onsager and Debye functions were established. These relationships were used to estimate dielectric constants for various environmentally benign esters.

  • 289.
    Varriale, Simona
    et al.
    Department of Chemical Sciences, Complesso Universitario Monte S. Angelo, University of Naples Federico II, Naples, Italy.
    Cerullo, Gabriella
    Department of Chemical Sciences, Complesso Universitario Monte S. Angelo, University of Naples Federico II, Naples, Italy.
    Antonopoulou, Io
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Tron, Thierry
    Centrale Marseille, CNRS, Aix Marseille Université, Marseille, France.
    Fauré, Régis
    LISBP, CNRS, INRA, INSA, Université de Toulouse, Toulouse, France.
    Jütten, Peter
    Taros Chemicals GmbH & Co. KG, Dortmund, Germany.
    Piechot, Alexander
    Taros Chemicals GmbH & Co. KG, Dortmund, Germany.
    Brás, Joana L A
    NzyTech LDA, Lisbon, Portugal.
    Fontes, Carlos M G A
    NzyTech LDA, Lisbon, Portugal.
    Faraco, Vincenza
    Department of Chemical Sciences, Complesso Universitario Monte S. Angelo, University of Naples Federico II, Naples, Italy .
    Evolution of the feruloyl esterase MtFae1a from Myceliophthora thermophila towards improved catalysts for antioxidants synthesis2018Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The chemical syntheses currently employed for industrial purposes, including in the manufacture of cosmetics, present limitations such as unwanted side reactions and the need for harsh chemical reaction conditions. In order to overcome these drawbacks, novel enzymes are developed to catalyze the targeted bioconversions. In the present study, a methodology for the construction and the automated screening of evolved variants library of a Type B feruloyl esterase from Myceliophthora thermophila (MtFae1a) was developed and applied to generation of 30,000 mutants and their screening for selecting the variants with higher activity than the wild-type enzyme. The library was generated by error-prone PCR of mtfae1a cDNA and expressed in Saccharomyces cerevisiae. Screening for extracellular enzymatic activity towards 4-nitrocatechol-1-yl ferulate, a new substrate developed ad hoc for high-throughput assays of feruloyl esterases, led to the selection of 30 improved enzyme variants. The best four variants and the wild-type MtFae1a were investigated in docking experiments with hydroxycinnamic acid esters using a model of 3D structure of MtFae1a. These variants were also used as biocatalysts in transesterification reactions leading to different target products in detergentless microemulsions and showed enhanced synthetic activities, although the screening strategy had been based on improved hydrolytic activity.

  • 290.
    Vouyiouka, Stamatina
    et al.
    National Technical University of Athens.
    Topakas, Evangelos
    National Technical University of Athens.
    Katsini, Adamantia
    National Technical University of Athens.
    Papaspyrides, Constantine
    National Technical University of Athens.
    Christakopoulos, Paul
    A green route for the preparation of aliphatic polyesters via lipase-catalyzed prepolymerization and low-temperature post polymerization2013Inngår i: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 298, nr 6, s. 679-689Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lipase-catalyzed polycondensation of two biobased diacids, 1,12-dodecanedioic acid and 1,14-tetradecanedioic acid, with 1,8-octanediol was achieved using immobilized Lipase B from Candida antarctica. The procedure resulted in partially renewable prepolymers, while poly(octylene adipate) from petroleum-based adipic acid was also synthesized for comparison reasons, revealing a dependence of the enzymatic polymerization degree on monomer composition. The prepolymers were further submitted to bulk postpolymerization at temperatures in the vicinity of their melting point under flowing nitrogen. The intrinsic viscosity increase was found up to 12%, with no significant impact on the polyesters thermal properties.

  • 291.
    Wang, F.
    et al.
    Michigan State University.
    Berglund, Kris
    Monitoring pH swing crystallization of nicotinic acid by the use of attenuated total reflection Fourier transform infrared spectrometry2000Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 39, nr 6, s. 2101-2104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nicotinic acid is crystallized by adding hydrochloric acid (HCl) to a sodium nicotinate aqueous solution. An attenuated total reflection Fourier transform infrared spectrometer is used to monitor the crystallization process of nicotinic acid. The partial least squares method is employed for IR data analysis. The solubility of nicotinic acid varies with the pH and the concentration of sodium nicotinate. The ability to measure the concentration and solubility of nicotinic acid in situ in aqueous mixtures of nicotinic acid and sodium nicotinate provides the possibility of controlling the degree of supersaturation of the solution and in turn optimizing the crystallization conditions for nicotinic acid.Nicotinic acid is crystallized by adding hydrochloric acid (HCl) to a sodium nicotinate aqueous solution. An attenuated total reflection Fourier transform infrared spectrometer is used to monitor the crystallization process of nicotinic acid. The partial least squares method is employed for IR data analysis. The solubility of nicotinic acid varies with the pH and the concentration of sodium nicotinate. The ability to measure the concentration and solubility of nicotinic acid in situ in aqueous mixtures of nicotinic acid and sodium nicotinate provides the possibility of controlling the degree of supersaturation of the solution and in turn optimizing the crystallization conditions for nicotinic acid.

  • 292.
    Wang, F.
    et al.
    Michigan State University.
    Wachter, J.A.
    Pharmacia Corporation, Kalamazoo, MI.
    Antosz, F.J.
    Pharmacia Corporation, Kalamazoo, MI.
    Berglund, Kris
    An investigation of solvent-mediated polymorphic transformation of progesterone using in situ Raman spectroscopy2000Inngår i: Organic Process Research & Development, ISSN 1083-6160, E-ISSN 1520-586X, Vol. 4, nr 5, s. 391-395Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many analytical techniques, such as differential scanning calorimetry (DSC), X-ray diffraction (XRD), infrared spectroscopy (IR) and Raman spectroscopy can be used to differentiate between crystalline polymorphs of the same chemical entity. While all of these techniques are routinely applied to off-line analysis of materials, Raman spectroscopy has the advantage over these other techniques in that Raman technology currently exists for in situ monitoring of the solid-phase behavior within a mixed suspension of liquid and solid. In this work, we present our results from an in situ Raman study, demonstrating the solvent-mediated polymorphic phase transformation of progesterone. In situ Raman analysis has shown that the appearance of Form I progesterone is always preceded by the formation of Form II progesterone. Phase transformation rates were found to increase monotonically as the temperature increases, which indicates that the polymorphic system is monotropic. Form I was found to be thermodynamically more stable than Form II, while Form II was found to be kinetically favored over Form I. The results from this study are consistent with Ostwald's law of stages and lead to an in-depth understanding of the polymorphic transformation process of progesterone. The in situ monitoring capabilities of Raman spectroscopy have allowed us to define the processing parameters required to control the morphology of crystalline progesterone.

  • 293.
    Wang, Zhao
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Recalcitrance of wood to biochemical conversion: feedstock properties, pretreatment, saccharification, and fermentability2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lignocellulose is an inexpensive and abundant renewable resource that can be used to produce advanced biofuels, green chemicals, and other bio-based products. Pretreatment and efficient enzymatic saccharification are essential features of bioconversion of lignocellulosic biomass. The aims of the research were to achieve a better understanding of the recalcitrance of woody biomass to bioconversion, to explore different pretreatment techniques that can be used to decrease the recalcitrance of the biomass and improve the digestibility of the cellulose, and to investigate by-products of acid pretreatment that cause enzymes and microorganisms to work less efficiently.

    The recalcitrance of wood from aspen, birch, and spruce was investigated before and after acid pretreatment. Before pretreatment, birch exhibited the highest recalcitrance, which was attributed to structural factors. After pretreatment, spruce showed the highest recalcitrance, which was attributed to chemical factors, such as high lignin content. Deacetylation of hybrid aspen in planta by a CE5 acetyl xylan esterase decreased the recalcitrance, and the glucose yield of enzymatic saccharification of non-pretreated wood increased with 27%.

    Pretreatment options based on ionic liquids and steam explosion were further explored. The effects of the anionic constituents of a series of imidazolium-based ionic liquids on pretreatment of aspen and spruce were investigated. [HSO4]− was efficient only for aspen, which was attributed to acid degradation of xylan. [MeCO2]− was efficient for both aspen and spruce, which was attributed to its capability to create a disordered cell wall structure rather than to removal of lignin and hemicellulose. A comparison was made between using sulfuric acid and sulfur dioxide for pretreatment of spruce. Although sulfur dioxide resulted in a pretreatment liquid that was more inhibitory to both enzymes and yeast, it was still superior to pretreatment with sulfuric acid, a phenomenon that was attributed to the particle size of the pretreated material.

    In a comparison of microbial inhibitors in pretreatment liquids from steam explosion of spruce, formaldehyde was found to be the most important inhibitor of yeast. Enzyme inhibition by catalytically non-productive adsorption to lignins and pseudo-lignin was investigated using quantitative proteomics. The results indicate that protein adsorption to pseudo-lignin can be as extensive as adsorption to real lignin. 

    Fulltekst tilgjengelig fra 2019-03-06 00:01
  • 294.
    Williams, Daniel L.
    et al.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Crowe, Jacob D.
    Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing.
    Ong, Rebecca G.
    Department of Chemical Engineering, Michigan Technological University, Houghton, MI.
    Hodge, David
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Water Sorption in Pretreated Grasses as a Predictor of Enzymatic Hydrolysis Yields2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 245, s. 242-249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work investigated the impact of two alkaline pretreatments, ammonia fiber expansion (AFEX) and alkaline hydrogen peroxide (AHP) delignification performed over a range of conditions on the properties of corn stover and switchgrass. Changes in feedstock properties resulting from pretreatment were subsequently compared to enzymatic hydrolysis yields to examine the relationship between enzymatic hydrolysis and cell wall properties. The pretreatments function to increase enzymatic hydrolysis yields through different mechanisms; AFEX pretreatment through lignin relocalization and some xylan solubilization and AHP primarily through lignin solubilization. An important outcome was that while changes in lignin content in AHP-delignified biomass could be clearly correlated to improved response to hydrolysis, compositional changes alone in AFEX-pretreated biomass could not explain differences in hydrolysis yields. We determined the water retention value, which characterizes the association of water with the cell wall of the pretreated biomass, can be used to predict hydrolysis yields for all pretreated biomass.

  • 295. Xiros, C.
    et al.
    Christakopoulos, Paul
    Biotechnological potential of brewers spent grain and its recent applications2012Inngår i: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265X, Vol. 3, nr 2, s. 213-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Brewers spent grain (BSG) is a by-product of the brewing process corresponding to around 85% of total by-products generated. The great number of publications over the last 5 years, on the biotechnological applications of BSG, represents the increased scientific interest on it. This critical, state of the art review aims at gathering and analysing the most recent scientific efforts on the biotechnological potential of Brewer’s spent grain and on its evaluation as a feedstock for high added value products.MethodsThe assiduous bibliographic retrospection focused on the latest scientific reports. The consideration of all relevant scientific articles was thorough and critical. The classification of the scientific efforts was made not only according to the end-products but also according to the biotechnological approach adopted.ResultsBSG has been used in a wide range of biotechnological applications such as substrate for enzymes production, as a source for value-added products (antioxidants, monosaccharides, oligosaccharides, xylitol, arabitol, bioethanol, biogas or lactic acid) or for the production of functional proteins and lipids. Its applications as a carrier in various bioprocesses have also been reported.ConclusionThe implementation of BSG’s fractionation in industrial scale seems to be the next step in BSG’s exploitation. A fractionation process which allows the exploitation of biomolecules belonging to different classes, produced from one feedstock (BSG) may be used as a pattern for the implementation of the biorefinery concept in industrial scale, as long as the methods adopted ensure the functionality of the potentially valuable components.

  • 296.
    Xiros, Charilaos
    et al.
    National Technical University of Athens, Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Topakas, Evangelos
    National Technical University of Athens, School of Chemical Engineering, National Technical University of Athens, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hydrolysis and Fermentation for Cellulosic Ethanol Production2016Inngår i: Advances in Bioenergy: The Sustainability Challenge, Chichester, UK: John Wiley & Sons Ltd , 2016, s. 11-31Kapittel i bok, del av antologi (Fagfellevurdert)
  • 297.
    Xiros, Charilaos
    et al.
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Topakas, Evangelos
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hydrolysis and fermentation for cellulosic ethanol production2013Inngår i: Wiley Interdisciplinary Reviews: Energy and Environment, ISSN 2041-8396, E-ISSN 2041-840X, Vol. 2, nr 6, s. 633-654Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Second-generation bioethanol produced from various lignocellulosic materials, such as wood, agricultural, or forest residues, has the potential to be a valuable substitute for, or a complement to, gasoline. At least three major factors—rapidly increasing atmospheric CO2 levels, dwindling fossil fuel reserves, and their rising costs—suggest that we now need to accelerate research plans to make greater use of plant-based biomass for energy production and as a chemical feedstock as part of a sustainable energy economy. Optimizing the production of bioethanol to be competitive with petrochemical fuels is the main challenge for the underlying process development. The exhaustive research on enzyme technology during the latest years, resulting in significant advances in the field, show the importance of the enzymatic hydrolysis for a profitable ethanol production process. On the other hand, the persisting challenges in biomass pretreatment, which are the initial steps in most process designs, show the remarkable recalcitrance of the lignocellulosic materials to biological degradation. The recent scientific trends show toward an integrated overall bioconversion process in which fermentation technology and genetic engineering of ethanologenic microorganisms aim not only at maximizing yields and productivities but also at widening the range of fermentation products and applications.

  • 298.
    Xiros, Charilaos
    et al.
    National Technical University of Athens.
    Vafiadi, Christina
    National Technical University of Athens.
    Topakas, Evangelos
    National Technical University of Athens.
    Christakopoulos, Paul
    Decrement of cellulose recalcitrance by treatment with ionic liquid (1-ethyl-3-methylimidazolium acetate) as a strategy to enhance enzymatic hydrolysis2012Inngår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 87, nr 5, s. 629-634Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND: The high crystallinity of cellulose underlies the recalcitrance that this polymer presents in enzymatic degradation. Thus, a pre-treatment step is applied in most bioconversion processes. Treatments with ionic liquids are considered an emerging pre-treatment technology, owing to their high efficiency in solvating cellulose, over molecular solvent systems.RESULTS: Crystalline cellulose with and without ionic liquid (1-ethyl-3-methylimidazolium acetate) treatment, both commercially available, were used as substrates in enzymatic hydrolysis reactions using the earlier evaluated cellulolytic system of Fusarium oxysporum. The in situ removal of the hydrolysate during reactions enhanced the reaction rate as well as the overall glucose production. Ionic liquid treatment significantly decreased cellulose crystallinity and enhanced bioconversion yields and rates. The effects of cellulose structural changes during treatment on hydrolysis rate were investigated and the recalcitrance constants were determined.CONCLUSION: The study showed that ionic liquid-treated cellulose became more homogeneous and more easily degradable than the untreated cellulose, a conclusion that was expressed mathematically by the difference in the recalcitrance constants for the two substrates. It was concluded that glucose production from ionic liquid-treated cellulose could achieve very high conversion yields in consolidated bioprocesses or during simultaneous saccharification and fermentation

  • 299.
    Yedur, Sanjay K
    et al.
    Michigan State University.
    Berglund, Kris
    Use of fluorescence spectroscopy in concentration and supersaturation measurements in citric acid solutions1996Inngår i: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 50, nr 7, s. 866-870Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurement of supersaturation is of critical importance in the operation and control of crystallizers. In this work, we report a novel spectroscopic technique to achieve the measurement of concentration and supersaturation in crystallizing solutions. In order to develop a sensor for this measurement, citric acid is chosen as the model solute, and the analytical technique involves fluorescence spectroscopy. Citric acid is a common food-grade compound with a wide range of applications that is exclusively produced by crystallization. The fluorescent properties of a probe, 8-hydroxy-1,3,6-pyrenetrisulfonate (pyranine), are used to provide concentration measurements in aqueous citric acid solutions, thereby providing for supersaturation estimation. The change in the relative emission peak intensities of the probe in different solute concentrations gives an excellent calibration curve for concentration measurements. It is also shown that, although pyranine responds to both its solvent microenvironment and the pH of the solution, it is still possible to measure concentration and supersaturation by using this fluorescence technique.

  • 300.
    Yedur, Sanjay K.
    et al.
    Michigan State University.
    Dulebohn, Joel
    Grand River Technologies, Lansing, MI.
    Werpy, Todd
    Michigan Biotechnology Institute, Lansing.
    Berglund, Kris
    Synthesis and testing of catalysts for the production of maleic anhydride from a fermentation feedstock1996Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 35, nr 3, s. 663-671Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is necessary to develop alternate pathways for the production of chemicals that are traditionally produced from fossil fuels to reduce our dependency on nonrenewable energy sources. In this paper, an alternate technology is presented for producing maleic anhydride from a fermentation feedstock. The process involves the catalytic oxydehydrogenation of fermentation-derived succinic anhydride to produce maleic anhydride. Various catalysts have been synthesized and tested for the oxydehydrogenation reaction. Iron phosphate based catalysts are found to be the best on the basis of high conversions and selectivities obtained. The effects of temperature, oxygen concentration, contact time, and the total time on stream on the performance of the catalyst are investigated, and an optimum set of conditions for the operation of the bench-scale reactor is presented. The bulk and surface compositions, the surface areas, and the bulk crystallographic structure of the catalysts are also reported.

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