Cloning and characterization of poly(3‐hydroxybutyrate) biosynthesis genes from Pseudomonas sp. USM 4‐55

Pseudomonas sp. USM 4‐55 is a locally isolated bacterium that possesses the ability to produce polyhydroxyalkanoates (PHA) consisting of both poly(3‐hydroxybutyrate) [P(3HB)] homopolymer and medium‐chain length (mcl) monomers (6 to 14 carbon atoms) when sugars or fatty acids are utilized as the sole carbon source. In this study, the P(3HB) biosynthesis operon carrying the phbC_Ps P(3HB) synthase was successfully cloned and sequenced using a homologous probe. Three open reading frames encoding NADPH‐dependent acetoacetyl‐coenzyme A reductase (PhbB_Ps), β‐ketothiolase (PhbA_Ps) and P(3HB) synthase (PhbC_Ps) were found in the phb operon. The genetic organization of phb operon showed a putative promoter region, followed by phbB_Ps‐phbA_Ps‐phbC_Ps. phbR_Pswhich encoded a putative transcriptional activator was located in the opposite orientation, upstream of phbBAC_Ps. Heterologous expression of pGEM″ABex harboring phbC_Ps in Escherichia coli JM109 resulted in P(3HB) accumulation of up to 40% of dry cell weight (DCW). (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)