Characterization of newly isolated thermotolerant bacterium Cupriavidus sp . CB15 from composting and its ability to produce polyhydroxyalkanoate from glycerol

Background This study aimed to isolate a novel thermotolerant bacterium that is capable of synthesizing polyhydroxyalkanoate from glycerol under high temperature conditions. Results A newly thermotolerant polyhydroxyalkanoate (PHA) producing bacterium, Cupriavidus sp . strain CB15, was isolated from corncob compost. The potential ability to synthesize PHA was confirmed by detection of PHA synthase ( phaC ) gene in the genome. This strain could produce poly(3-hydroxybutyrate) [P(3HB)] with 0.95 g/L (PHA content 75.3 wt% of dry cell weight 1.24 g/L) using glycerol as a carbon source. The concentration of PHA was enhanced and optimized based on one-factor-at-a-time (OFAT) experiments and response surface methodology (RSM). The optimum conditions for growth and PHA biosynthesis were 10 g/L glycerol, 0.78 g/L NH 4 Cl, shaking speed at 175 rpm, temperature at 45 °C, and cultivation time at 72 h. Under the optimized conditions, PHA production was enhanced to 2.09 g/L (PHA content of 74.4 wt% and dry cell weight of 2.81 g/L), which is 2.12-fold compared with non-optimized conditions. Nuclear magnetic resonance (NMR) analysis confirmed that the extracted PHA was a homopolyester of 3-hydyoxybutyrate. Conclusion Cupriavidus sp . strain CB15 exhibited potential for cost-effective production of PHA from glycerol.