Production of poly-(R)-3-hydroxybutyrate from halophilic bacterium Salinivibrio sp. utilizing palm oil mill effluent as a carbon source

Abstract

The accumulation of plastic waste has become an emerging threat to the ecosystem. Reducing plastic waste can be overcome by replacing petrochemical-based plastics with biodegradable ones, such as poly-(R)-3-hydroxybutyrate (PHB). In the present study, we have successfully isolated, characterized, and optimized the PHB yield produced by halophilic bacteria isolated from salt lake Gili Meno, Lombok, Indonesia, utilizing palm oil mill effluent (POME) as the carbon source. Bacterial screening found that isolated bacteria from the bottom of the lake produced the highest PHB yield, mainly when the bacterial isolate was grown in the medium containing 15% (v/v) POME, 5% (w/v) NaCl, as well as 0.1% (w/v) yeast, and 0.1% (w/v) ammonium sulfate. The highest PHB yield produced by the bacterial isolate in this medium was about 5.0 ± 0.8 mg/L. Ribotyping has identified the bacterial isolate as Salinivibrio sp. with 99.9% similarity to the 16S rRNA gene of Salinivibrio sp. YCSC6 (GenBank accession no. CP039516.1). Scanning electron microscope images of the produced PHB exhibited the morphology of sheet-like structures. Thermal analysis revealed that the produced PHB has maximum decomposition and degradation temperatures at 442.4 °C and 282.9 °C, respectively. Therefore, Salinivibrio sp. is a potential bacterial isolate for producing high-yield PHB with high thermal stability. In addition, this bacterial strain is also a productive bacterium in bio-converting POME into PHB, thereby resolving the environmental issue of liquid waste from palm oil industries.