Isolation and characterization of two halophilic bacteria producing polyhydroxybutyrate from high-salt environment

Polyhydroxyalkanoates (PHAs), one of biodegradable polyesters, are substances that store carbon and energy in various microorganisms. Polyhydroxybutyrate (PHB) is the most commonly type of PHAs with relatively simple chemical structure. In this study, we developed a polymerase chain reaction (PCR) screening method for screen novel halophilic bacteria containing PHA synthase (PhaC) gene. Halophilic bacteria were collected and isolated from high-salt environment such as sea soil or shrimp jeotgal in South Korea. Primer set was designed based on the conserved region in Class I PhaC from 30 kinds of Halomonas species. The designed primer set was used to optimize PCR conditions to identify PhaC gene in newly isolated 15 halophilic bacteria from sea soil or shrimp jeotgal. Among 15 candidates, five bacteria were selected after PCR and agarose gel analysis and confirmed to produce PHB. Two bacteria with higher PHB production were identified as Halomonas and Marinobacter sp. by 16 s rRNA analysis and named as Halomonas shrimpha IBTH01 and Marinobacter haeunpha IBTM02. Then, PHB production was examined by changing culture temperature, media composition, carbon source, and glucose concentration. Finally, PHB from two bacteria was analyzed by transmission electron microscopy, gas chromatography, and ¹H nuclear magnetic resonance. Taken together, this study will contribute to establish a platform for the utilization of novel halophilic bacteria in the synthesis of PHA polymers.