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  • 1.
    Ahlén, Gustaf
    et al.
    Recopharma AB.
    Strindelius, Lena
    Recopharma AB.
    Johansson, Tomas
    Recopharma AB.
    Nilsson, Anki
    Rrecopharma AB.
    Chatzissavidou, Nathalie
    Recopharma AB.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holsgersson, Jan
    Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy.
    Mannosylated mucin-type immunoglobulin fusion proteins enhance antigen-specific antibody and T lymphocyte responses2012Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Targeting antigens to antigen-presenting cells (APC) improve their immunogenicity and capacity to induce Th1 responses and cytotoxic T lymphocytes (CTL). We have generated a mucin-type immunoglobulin fusion protein (PSGL-1/mIgG2b), which upon expression in the yeast Pichia pastoris became multivalently substituted with O-linked oligomannose structures and bound the macrophage mannose receptor (MMR) and dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) with high affinity in vitro. Here, its effects on the humoral and cellular anti-ovalbumin (OVA) responses in C57BL/6 mice are presented.OVA antibody class and subclass responses were determined by ELISA, the generation of anti-OVA CTLs was assessed in 51Cr release assays using in vitro-stimulated immune spleen cells from the different groups of mice as effector cells and OVA peptide-fed RMA-S cells as targets, and evaluation of the type of Th cell response was done by IFN-γ, IL-2, IL-4 and IL-5 ELISpot assays.Immunizations with the OVA − mannosylated PSGL-1/mIgG2b conjugate, especially when combined with the AbISCO®-100 adjuvant, lead to faster, stronger and broader (with regard to IgG subclass) OVA IgG responses, a stronger OVA-specific CTL response and stronger Th1 and Th2 responses than if OVA was used alone or together with AbISCO®-100. Also non-covalent mixing of mannosylated PSGL-1/mIgG2b, OVA and AbISCO®-100 lead to relatively stronger humoral and cellular responses. The O-glycan oligomannoses were necessary because PSGL-1/mIgG2b with mono- and disialyl core 1 structures did not have this effect.Mannosylated mucin-type fusion proteins can be used as versatile APC-targeting molecules for vaccines and as such enhance both humoral and cellular immune responses.

  • 2.
    Christakopoulos, Paul
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Topakas, Evangelos
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Project: BIOcatalytic Carbon Capture and Conversion of steel flue gas to liquid hydrocarbons (FORMAS)2016Annet (Annet (populærvitenskap, debatt, mm))
  • 3.
    Gustafsson, Anki
    et al.
    Recopharma AB, Huddinge.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Strindelius, Lena
    Recopharma AB, Huddinge.
    Johansson, Thomas
    Recopharma AB, Huddinge.
    Fleckenstein, Tilly
    Recopharma AB, Huddinge.
    Chatzissavidou, Nathalie
    Recopharma AB, Huddinge.
    Lindberg, Linda
    Absorber AB, Stockholm.
    Ångström, Jonas
    Göteborgs universitet.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holgersson, Jan
    Karolinska Institutet.
    Pichia pastoris-produced mucin-type fusion proteins with multivalent O-glycan substitution as targeting molecules for mannose-specific receptors of the immune system2011Inngår i: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 21, nr 8, s. 1071-1086Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mannose-binding proteins like the macrophage mannose receptor (MR), the dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) and mannose-binding lectin (MBL) play crucial roles in both innate and adaptive immune responses. Immunoglobulin fusion proteins of the P-selectin glycoprotein ligand-1 (PSGL-1/mIgG2b) carrying mostly O-glycans and, as a control, the a1-acid glycoprotein (AGP/mIgG2b) carrying mainly N-linked glycans were stably expressed in the yeast Pichia pastoris. P. pastoris-produced PSGL-1/mIgG2b was shown to carry O-glycans that mediated strong binding to mannose-specific lectins in a lectin array and were susceptible to cleavage by a-mannosidases including an a1,2- but not an a1,6-mannosidase. Electrospray ionization - ion trap mass spectrometry (ESI-MS) confirmed the presence of O-glycans containing up to 9 hexoses with the penta- and hexasaccharides being the predominant ones. a1,2- and a1,3-linked, but not a1,6-linked, mannose residues were detected by 1H-nuclear magnetic resonance (1H-NMR) spectroscopy confirming the results of the mannosidase cleavage. The apparent equilibrium dissociation constants for binding of PNGase F-treated mannosylated PSGL-1/mIgG2b to MR, DC-SIGN and MBL were shown by surface plasmon resonance to be 126, 56 and 16 nM, respectively. In conclusion, PSGL-1/mIgG2b expressed in P. pastoris carried O-glycans mainly comprised of a-linked mannoses and with up to nine residues. It bound mannose-specific receptors with high apparent affinity and may become a potent targeting molecule for these receptors in vivo.

  • 4.
    Kenny, Diarmuid T.
    et al.
    School of Chemistry and Medical Biochemistry, National University Ireland Galway.
    Gaunitz, Stefan
    Division of Clinical Immunology and Transfusion Medicine, Karolinska Institute.
    Hayes, Catherine A.
    Medical Biochemistry, University of Gothenburg.
    Gustafsson, Anki
    Recopharma AB, Stockholm.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holgersson, Jan
    Absorber AB, Stockholm.
    Karlsson, Niclas G.
    Medical Biochemistry, University of Gothenburg.
    Mass Spectrometric Analysis of O-Linked Oligosaccharides from Various Recombinant Expression Systems2013Inngår i: Glycosylation Engineering of Biopharmaceuticals: Methods and Protocols, New York: Humana Press, 2013, s. 145-167Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Analysis of O-linked glycosylation is one of the main challenges during structural validation of recombinant glycoproteins. With methods available for N-linked glycosylation in regard to oligosaccharide analysis as well as glycopeptide mapping, there are still challenges for O-linked glycan analysis. Here, we present mass spectrometric methodology for O-linked oligosaccharides released by reductive β-elimination. Using LC-MS and LC-MS2 with graphitized carbon columns, oligosaccharides are analyzed without derivatization. This approach provides a high-throughput method for screening during clonal selection, as well as product structure verification, without impairing sequencing ability. The protocols are exemplified by analysis of glycoproteins from mammalian cell cultures (CHO cells) as well as insect cells and yeast. The data shows that the method can be successfully applied to both neutral and acidic O-linked oligosaccharides, where sialic acid, hexuronic acid, and sulfate are common substituents. Further characterization of O-glycans can be achieved using permethylation. Permethylation of O-linked oligosaccharides followed by direct infusion into the mass spectrometer provide information about oligosaccharide composition, and subsequent MSn experiments can be carried out to elucidate oligosaccharide structure including linkage information and sequence.

  • 5.
    Krige, Adolf
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Ramser, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Christakopoulos, Paul
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    On-line Raman spectroscopic study of cytochromes’ redox state of biofilms in microbial fuel cells2019Inngår i: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 24, nr 3, artikkel-id 646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bio-electrochemical systems such as microbial fuel cells and microbial electrosynthesis cells depend on efficient electron transfer between the microorganisms and the electrodes. Understanding the mechanisms and dynamics of the electron transfer is important in order to design more efficient reactors, as well as modifying microorganisms for enhanced electricity production. Geobacter are well known for their ability to form thick biofilms and transfer electrons to the surfaces of electrodes. Currently, there are not many “on-line” systems for monitoring the activity of the biofilm and the electron transfer process without harming the biofilm. Raman microscopy was shown to be capable of providing biochemical information, i.e., the redox state of C-type cytochromes, which is integral to external electron transfer, without harming the biofilm. In the current study, a custom 3D printed flow-through cuvette was used in order to analyze the oxidation state of the C-type cytochromes of suspended cultures of three Geobacter sulfurreducens strains (PCA, KN400 and ∆pilA). It was found that the oxidation state is a good indicator of the metabolic state of the cells. Furthermore, an anaerobic fluidic system enabling in situ Raman measurements was designed and applied successfully to monitor and characterize G. sulfurreducens biofilms during electricity generation, for both a wild strain, PCA, and a mutant, ∆S. The cytochrome redox state, monitored by the Raman peak areas, could be modulated by applying different poise voltages to the electrodes. This also correlated with the modulation of current transferred from the cytochromes to the electrode. The Raman peak area changed in a predictable and reversible manner, indicating that the system could be used for analyzing the oxidation state of the proteins responsible for the electron transfer process and the kinetics thereof in-situ. 

  • 6.
    Kudahettige-Nilsson, Rasika
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Helmerius, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Nilsson, Robert
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Sjöblom, Magnus
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hodge, David
    Rova, Ulrika
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Biobutanol Production by Clostridium acetobutylicum Using Xylose Recovered from Birch Kraft Black Liquor2015Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 176, s. 71-79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acetone-Butanol-Ethanol (ABE) fermentation was studied using acid-hydrolyzed xylan recovered from hardwood Kraft black liquor by CO2 acidification as the only carbon source. Detoxification of hydrolyzate using activated carbon was conducted to evaluate the impact of inhibitor removal and fermentation. Xylose hydrolysis yields as high as 18.4% were demonstrated at the highest severity hydrolysis condition. Detoxification using active carbon was effective for removal of both phenolics (76-81%) and HMF (38-52%). Batch fermentation of the hydrolyzate and semi-defined P2 media resulted in a total solvent yield of 0.12-0.13 g/g and 0.34 g/g, corresponding to a butanol concentration of 1.8-2.1 g/L and 7.3 g/L respectively. This work is the first study of a process for the production of a biologically-derived biofuel from hemicelluloses solubilized during Kraft pulping and demonstrates the feasibility of utilizing xylan recovered directly from industrial Kraft pulping liquors as a feedstock for biological production of biofuels such as butanol.

  • 7.
    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)
  • 8.
    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.

  • 9.
    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)
  • 10.
    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.

  • 11.
    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.

  • 12.
    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.

  • 13.
    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

  • 14.
    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.

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