The Halophilic Bacterium for the Production of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) from Single Carbon Sources.

The study objective was to evaluate the potential production of polyhydroxyalkanoates (PHAs), a biodegradable plastic material, by for which PHA production has never been reported. To identify the most effective nitrogen-limited culture conditions for PHAs production from this bacterium, batch fermentation using glucose concentrations ranging from 4 g l to 20 g l with a fixed ammonium concentration of 0.5 g l was carried out at 30°C and pH 8.0. A glucose supplement of 12 g l produced the highest PHA concentration (1.6 g l) and PHA content (0.63 g g) thereby identifying the optimal condition for PHA production from this bacterium. Gas chromatography-mass spectrometry analysis suggests that mostly produced copolymer types of poly(3-hydroxybutyrate--3-hydroxyvalerate) [P(3HB--3HV)] from glucose concentrations at 12 g l or higher under the nitrogen-limited conditions. When several other single carbon sources were evaluated for the most efficient PHA production, fructose provided the highest biomass (2.8 g l), and PHAs (1.29 g l) concentrations. Results indicated that this bacterium mostly produced the copolymers P(3HB--3HV) from single carbon sources composing a range of 93-98% of 3-hydroxybutyrate and 2-7% of 3-hydroxyvalerate, whereas mannose-supplemented conditions produced the only homopolymer type of P(3HB). However, when propionic acid as a secondary carbon source were supplemented into the media, produced the copolymer P(3HB--3HV), composed of a 50% maximum monomeric unit of 3-hydroxyvaleric acid (3HV). However, as the concentration of propionic acid increased, cell biomass and PHAs concentrations substantially decreased due to cell toxicity.