Propionic acid metabolism and poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P3HB-co-3HV) production by Burkholderia sp.

Mutants of Burkholderia sp. that are unable to grow on propionic acid (prp) but still accumulate P3HB-co-3HV from carbohydrate and propionic acid were studied. In shaken flask tests, yields of 3HV from propionic acid (Y(3HV/Prop)) increased from 0.10 g g(-1) in the wild type to c.a. 0.35 g g(-1) in mutants affected in alpha-oxidation pathway or to 0.80 g g(-1) in mutants not affected in that pathway. In bioreactor tests, mutant IPT 189 showed Y(3HV/Prop) = 1.20 g g(-1), a yield very close to the theoretical maximum of 1.35 g g(-1). Accumulation of 3HV units from unrelated carbon sources was undetectable in these mutants indicating that 3HV units are produced directly from propionic acid. Thus, the industrial use of those mutants to produce the copolymer from sucrose and propionic acid could significantly reduce the production costs. The results strongly suggest the existence of at least two pathways that are involved in the oxidation of propionic acid in Burkholderia sp. Their rates would be modulated by the availability of propionic acid.