Abstract
Six bacteria that synthesize medium-chain-length polyhydroxyalkanoates (mcl-PHAs) were isolated from sewage sludge and hog barn wash and identified as strains of Pseudomonas and Comamonas by 16S rDNA gene sequencing. One isolate, Pseudomonas putida LS46, showed good PHA production (22% of cell dry mass) in glucose medium, and it was selected for further studies. While it is closely related to other P.putida strains (F1, KT2440, BIRD-1, GB-1, S16, and W619), P.putida LS46 was genetically distinct from these other strains on the basis of nucleotide sequence analysis of the cpn60 gene hypervariable region. PHA production was detected as early as 12h in both nitrogen-limited and nitrogen-excess conditions. The increase in PHA production after 48h was higher in nitrogen-limited cultures than in nitrogen-excess cultures. Pseudomonasputida LS46 produced mcl-PHAs when cultured with glucose, glycerol, or C(6)-C(14) saturated fatty acids as carbon sources, and mcl-PHAs accounted for 56% of the cell dry mass when cells were batch cultured in medium containing 20mmol/L octanoate. Although 3-hydroxydecanoate was the major mcl-PHA monomer (58.1-68.8mol%) in P.putida LS46 cultured in glucose medium, 3-hydroxyoctanoate was the major monomer produced in octanoate medium (88mol%).
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