Enhanced co-production of hydrogen and poly-(R)-3-hydroxybutyrate by recombinant PHB producing E. coli over-expressing hydrogenase 3 and acetyl-CoA synthetase

Recombinant Escherichia coli was constructed for co-production of hydrogen and polyhydroxybutyrate (PHB) due to its rapid growth and convenience of genetic manipulation. In particular, anaerobic metabolic pathways dedicated to co-production of hydrogen and PHB were established due to the advantages of directing fluxes away from toxic compounds such as formate and acetate to useful products. Here, recombinant E. coli expressing hydrogenase 3 and/or acetyl-CoA synthetase showed improved PHB and hydrogen production when grown with or without acetate as a carbon source. When hydrogenase 3 was over-expressed, hydrogen yield was increased from 14 to 153mmol H₂/mol glucose in a mineral salt (MS) medium with glucose as carbon source, accompanied by an increased PHB yield from 0.55 to 5.34mg PHB/g glucose in MS medium with glucose and acetate as carbon source.