Bacterial poly(hydroxyalkanoate) polymer production from the biodiesel co-product stream

A co-product stream from soy-based biodiesel production (CSBP) containing glycerol, fatty acid soaps, and residual fatty acid methyl esters (FAME) was utilized as a fermentation feedstock for the bacterial synthesis of poly(3-hydroxybutyrate) (PHB) and medium-chain-length poly(hydroxyalkanoate) (mcl-PHA) polymers. Pseudomonas oleovorans NRRL B-14682 and P. corrugata 388 grew and synthesized PHB and mcl-PHA, respectively, when cultivated in up to 5% (w/v) CSBP. In shake flask culture, P. oleovorans grew to 1.3 +/- 0.1 g/L (PHA cellular productivity = 13-27% of the bacterial cell dry weight; CDW) regardless of the initial CSBP concentration, whereas P. corrugata reached maximum cell yields of 2.1 g/L at 1% CSBP, which tapered off to 1.7 g/L as the CSBP media concentration was increased to 5% (maximum PHA cellular productivity = 42% of the CDW at 3% CSBP). While P. oleovorans synthesized PHB from CSBP, P. corrugata produced mcl-PHA consisting primarily of 3-hydroxyoctanoic acid (C-8:0; 39 +/- 2 mol%), 3-hydroxydecanoic acid (C-10:0; 26 +/- 2 mol%) and 3-hydroxytetradecadienoic acid (C-14:2; 15 +/- 1 mol%). The molar mass (M-n) of the PHB polymer decreased by 53% as the initial CSBP culture concentration was increased from 1% to 5% (w/v). In contrast, the Mn of the mcl-PHA polymer produced by P. corrugata remained constant over the range of CSBP concentrations used.