Effect of nitrogen availability on the poly-3-d-hydroxybutyrate accumulation by engineered Saccharomyces cerevisiae


Poly-3-d-hydroxybutyrate (or PHB) is a polyester which can be used in the production of biodegradable plastics from renewable resources. It is naturally produced by several bacteria as a response to nutrient starvation in the excess of a carbon source.

The yeast Saccharomyces cerevisiae could be an alternative production host as it offers good inhibitor tolerance towards weak acids and phenolic compounds and does not depolymerize the produced PHB. As nitrogen limitation is known to boost the accumulation of PHB in bacteria, the present study aimed at investigating the effect of nitrogen availability on PHB accumulation in two recombinant S.

cerevisiae strains harboring different xylose consuming and PHB producing pathways: TMB4443 expressing an NADPH-dependent acetoacetyl-CoA reductase and a wild-type S. stipitis XR with preferential use of NADPH and TMB4425 which expresses an NADH-dependent acetoacetyl-CoA reductase and a mutated XR with a balanced affinity for NADPH/NADH.

TMB4443 accumulated most PHB under aerobic conditions and with glucose as sole carbon source, whereas the highest PHB concentrations were obtained with TMB4425 under anaerobic conditions and xylose as carbon source. In both cases, the highest PHB contents were obtained with high availability of nitrogen.

The major impact of nitrogen availability was observed in TMB4425, where a 2.7-fold increase in PHB content was obtained. In contrast to what was observed in natural PHB-producing bacteria, nitrogen deficiency did not improve PHB accumulation in S.

cerevisiae. Instead the excess available carbon from xylose was shunted into glycogen, indicating a significant gluconeogenic activity on xylose.



Published on: 2017-02-07

Made available by EUPB via SpringerOpen / BioMedCentral. Please make sure to read our disclaimer prior to contacting 7thSpace Interactive. To contact our editors, visit our online helpdesk. To submit your press release click here. The full research and author details are available at http://www.amb-express.com/content/7/1/35

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