Establishment of a gene transfer system for Rhodococcus opacus PD630 basedon electroporation and its application for recombinant biosynthesis of poly(3-hydroxyalkanoic acids)

A gene transfer system for Rhodococcus opacus PD630 based on electroporatio n was established and optimized employing the Escherichia coli-Rhodococcus shuttle vectors pNC9501 and pNC9503 as well as the E. coli-Corynebacterium glutamicum shuttle vector pJC1 as suitable cloning vectors for R. opacus PD 630, resulting in transformation efficiencies up to 1.5 x 10(5) CFUs/mu g p lasmid DNA. Applying the optimized electroporation protocol to the pNC9501- derivatives pAK68 and pAK71 harboring the entire PHB synthesis operon from Ralstonia eutropha and the PHA synthase gene phaC1 from Pseudomonas aerugin osa, respectively, recombinant PI-IA biosynthesis was established in R. opa cus PD630 and the TAG-negative mutant ROM34. Plasmid pAK68 enabled synthesi s and accumulation of poly(3HB) in R. opacus PD630 and ROM34 during cultiva tion under storage conditions from 1% (w/v) gluconate, of poly(3HB-co-3HV) from 0.2% (w/v) propionate and of poly(3HV) from 0.1% (w/v) valerate. Under storage conditions, recombinant strains of PD630 and ROM34 harboring pAK71 were able to synthesize and accumulate PHA of the medium chain length hydr oxyalkanoic acids 3HHx, 3HO, 3HD and 3HDD from 0.1% (w/v) hexadecane or oct adecane and a copolyester composed of 3HHp, 3HN and 3HUD from 0.1% (w/v) pe ntadecane or heptadecane. In the recombinant strains of PD630 and ROM34, th e thiostrepton-induced overexpression of a 20 kDa protein was observed with its N-terminus exhibiting a homology of 60% identical amino acids to TipA from Streptomyces lividans.