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Comparison of engineered Escherichia coli AF1000 and BL21 strains for (R)-3-hydroxybutyrate production in fed-batch cultivation
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). (Industrial Biotechnology)ORCID iD: 0000-0003-3873-4977
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). (Industrial Biotechnology)ORCID iD: 0000-0001-6501-9886
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). (Industrial Biotechnology)ORCID iD: 0000-0002-3314-6060
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2019 (English)In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 103, no 14, p. 5627-5636Article in journal (Refereed) Accepted
Abstract [en]

Accumulation of acetate is a limiting factor in recombinant production of (R)-3-hydroxybutyrate (3HB) by E. coli in high-cell-density processes. To alleviate this limitation, this study investigated two approaches: (i) Deletion of phosphotransacetylase (pta), pyruvate oxidase (poxB) and/or the isocitrate-lyase regulator (iclR), known to decrease acetate formation, on bioreactor cultivations designed to achieve high 3HB concentrations. (ii) Screening of different E. coli strain backgrounds (B, BL21, W, BW25113, MG1655, W3110 and AF1000) for their potential as low acetate-forming, 3HB-producing platforms. Deletion of pta and pta-poxB in the AF1000 strain background was to some extent successful in decreasing acetate formation, but also dramatically increased excretion of pyruvate and did not result in increased 3HB production in high-cell-density fed-batch cultivations. Screening of the different E. coli strains confirmed BL21 as a low acetate forming background. Despite low 3HB titers in low-cell density screening, 3HB-producing BL21 produced 5 times less acetic acid per mol of 3HB, which translated into a 2.3-fold increase in the final 3HB titer and a 3-fold higher volumetric 3HB productivity over 3HB-producing AF1000 strains in nitrogen-limited fed-batch cultivations. Consequently, the BL21 strain achieved the hitherto highest described volumetric productivity of 3HB (1.52 g L-1 h-1) and the highest 3HB concentration (16.3 g L-1) achieved by recombinant E. coli. Screening solely for 3HB titers in low-cell-density batch cultivations would not have identified the potential of this strain, reaffirming the importance of screening with the final production conditions in mind.

Place, publisher, year, edition, pages
Springer, 2019. Vol. 103, no 14, p. 5627-5636
Keywords [en]
Escherichia coli, (R)-3-hydroxybutyrate, acetate, nitrogen limitation, fed batch, BL21.
National Category
Engineering and Technology
Research subject
Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-251046DOI: 10.1007/s00253-019-09876-yISI: 000473129900012Scopus ID: 2-s2.0-85066078742OAI: oai:DiVA.org:kth-251046DiVA, id: diva2:1314440
Funder
Sida - Swedish International Development Cooperation Agency, 70828
Note

QC 20190508

Available from: 2019-05-08 Created: 2019-05-08 Last updated: 2019-08-15Bibliographically approved
In thesis
1. Metabolic engineering and cultivation strategies for recombinant production of (R)-3-hydroxybutyrate
Open this publication in new window or tab >>Metabolic engineering and cultivation strategies for recombinant production of (R)-3-hydroxybutyrate
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Metabolic engineering and process engineering are two powerful disciplines to design and improve microbial processes for sustainable production of an extensive number of compounds ranging from chemicals to pharmaceuticals. The aim of this thesis was to synergistically combine these two disciplines to improve the production of a model chemical called (R)-3-hydroxybutyrate (3HB), which is a medium-value product with a stereocenter and two functional groups. These features make 3HB an interesting building block, especially for the pharmaceutical industry. Recombinant production of 3HB was achieved by expression of two enzymes from Halomonas boliviensis in the model microorganism Escherichia coli, which is a microbial cell factory with proven track record and abundant knowledge on its genome, metabolism and physiology.

Investigations on cultivation strategies demonstrated that nitrogen-depleted conditions had the biggest impact on 3HB yields, while nitrogen-limited cultivations predominantly increased 3HB titers and volumetric productivities. To further increase 3HB production, metabolic engineering strategies were investigated to decrease byproduct formation, enhance NADPH availability and improve the overall 3HB-pathway activity. Overexpression of glucose-6-phosphate dehydrogenase (zwf) increased cofactor availability and together with the overexpression of acyl-CoA thioesterase YciA resulted in a 2.7-fold increase of the final 3HB concentration, 52% of the theoretical product yield and a high specific productivity (0.27 g g-1 h-1). In a parallel strategy, metabolic engineering and process design resulted in an E. coli BL21 strain with the hitherto highest reported volumetric 3HB productivity (1.52 g L-1 h-1) and concentration (16.3 g L-1) using recombinant production. The concepts developed in this thesis can be applied to industrial 3HB production processes, but also advance the knowledge base to benefit design and expansion of the product range of biorefineries.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 106
Series
TRITA-CBH-FOU ; 2019:20
Keywords
Escherichia coli, (R)-3-hydroxybutyrate, nitrogen limitation, nitrogen depletion, lignocellulose, fed batch, acetate, β-ketothiolase, acetoacetyl-CoA reductase, Halomonas boliviensis.
National Category
Engineering and Technology
Research subject
Biotechnology
Identifiers
urn:nbn:se:kth:diva-251048 (URN)978-91-7873-216-6 (ISBN)
Public defence
2019-06-05, FD5, AlbaNova, Roslagstullsbacken 21, SE-11421, Stockholm, Sweden, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency, 70828
Note

QC 2019-05-08

Available from: 2019-05-08 Created: 2019-05-08 Last updated: 2019-05-09Bibliographically approved
2. Strain- and bioprocess-design strategies to increase production of (R)-3-hydroxybutyrate by Escherichia coli
Open this publication in new window or tab >>Strain- and bioprocess-design strategies to increase production of (R)-3-hydroxybutyrate by Escherichia coli
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microbial bio-based processes have emerged as an alternative to replace fossil-based processes for the production of fuels and chemicals. (R)-3-hydroxybutyrate (3HB) is a medium-value chemical that has gained special attention as a precursor of antibiotics and vitamins, as a monomer for the synthesis of tailor-made polyesters and as a nutritional source for eukaryotic cells. By integrating strain and bioprocess-design strategies the work of this thesis has aimed to improve microbial 3HB production by the well-studied platform organism Escherichia coli (strain AF1000) expressing a thiolase and a reductase from Halomonas boliviensis.

Uncoupling growth and product formation by NH4+- or PO43-- limited fed-batch cultivations allowed for 3HB titers of 4.1 and 6.8 g L-1 (Paper I). Increasing the NADPH supply by overexpression of glucose-6-phosphate dehydrogenase (zwf) resulted in 1.7 times higher 3HB yield compared to not overexpressing zwf in NH4depleted conditions (Paper II). To increase 3HB production in high-cell density cultures, strain BL21 was selected as a low acetate-forming, 3HB-producing platform. BL21 grown in NH4limited fed-batch cultivations resulted in 2.3 times higher 3HB titer (16.3 g L-1) compared to strain AF1000 (Paper III). Overexpression of the native E. coli thioesterase “yciA”, identified as the largest contributor in 3HB-CoA hydrolysis, resulted in 2.6 times higher 3HB yield compared to AF1000 not overexpressing yciA. Overexpressing zwf and yciA in NH4depleted fed-batch experiments resulted in 2 times higher total 3HB yield (0.210 g g-1) compared to AF1000 only overexpressing zwf (Paper IV)Additionally, using 3HB as a model product, the bacterial artificial chromosome was presented as a simple platform for performing pathway design and optimization in E. coli (Paper V)While directly relevant for 3HB production, these findings also contribute to the knowledge on how to improve the production of a chemical for the development of robust and scalable processes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 100
Series
TRITA-CBH-FOU ; 2019:25
Keywords
E. coli, (R)-3-hydroxybutyrate, metabolic engineering, bioprocess design, NADPH, acetic acid, thioesterase, BAC
National Category
Industrial Biotechnology
Research subject
Biotechnology
Identifiers
urn:nbn:se:kth:diva-251096 (URN)978-91-7873-205-0 (ISBN)
Public defence
2019-06-03, F3, Lindstedtsvägen 26, Sing-Sing, våningsplan 2, KTH Campus, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation AgencySwedish Research Council Formas
Note

QC 2019-05-09

Available from: 2019-05-09 Created: 2019-05-09 Last updated: 2019-05-09Bibliographically approved

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