Cultivation strategies for production of (R)-3-hydroxybutyric acid from simultaneous consumption of glucose, xylose and arabinose by Escherichia coli
2015 (English)In: Microbial Cell Factories, ISSN 1475-2859, E-ISSN 1475-2859, Vol. 14, no 1, 51- p.Article in journal (Refereed) Published
Lignocellulosic waste is a desirable biomass for use in second generation biorefineries. Up to 40 % of its sugar content consist of pentoses, which organisms either take up sequentially after glucose depletion, or not at all. A previously described Escherichia coli strain, PPA652ara, capable of simultaneous consumption of glucose, xylose and arabinose was in the present work utilized for production of (R)-3-hydroxybutyric acid (3HB) from a mixture of glucose, xylose and arabinose.
The Halomonas boliviensis genes for 3HB production were for the first time cloned into E. coli PPA652ara leading to product secretion directly into the medium. Process design was based on comparisons of batch, fed-batch and continuous cultivation, where both excess and limitation of the carbon mixture was studied. Carbon limitation resulted in low specific productivity of 3HB (< 2 mg g-1 h-1) compared to carbon excess (25 mg g-1 h-1), but the yield of 3HB/cell dry weight (Y3HB/CDW) was very low (0.06 g g-1)during excess. Nitrogen-exhausted conditions could be used to sustain a high specific productivity (31 mg g-1 h-1) and to increase the yield of 3HB/cell dry weight to 1.38 g g-1. Nitrogen-limited fed-batch process design lead to further increased specific productivity (38 mg g-1 h-1) but also to additional cell growth (Y3HB/CDW = 0.16 g g-1). Strain PPA652ara did under all processing conditions simultaneously consume glucose, xylose and arabinose, which was not the case for a reference wild type E. coli, which also gave a higher carbon flux to acetic acid.
It was demonstrated that by using the strain E. coli PPA652ara it was possible to design a production process for 3HB from a mixture of glucose, xylose and arabinose where all sugars were consumed. An industrial 3HB production process is proposed to be divided into a growth and a production phase, and nitrogen depletion/limitation is a potential strategy to maximize the yield of 3HB/CDW in the latter. The specific productivity of 3HB by E. coli reported here from glucose, xylose and arabinose is further comparable to the current state of the art for production of 3HB from glucose sources.
Place, publisher, year, edition, pages
BioMed Central, 2015. Vol. 14, no 1, 51- p.
Escherichia coli, 3-Hydroxybutyric acid, 3HB, simultaneous uptake, lignocellulose, production process, nitrogen limitation
Research subject Biotechnology
IdentifiersURN: urn:nbn:se:kth:diva-166385DOI: 10.1186/s12934-015-0236-2ISI: 000353259300001ScopusID: 2-s2.0-84928231166OAI: oai:DiVA.org:kth-166385DiVA: diva2:810678
QC 201505082015-05-082015-05-082015-11-10Bibliographically approved