Production of medium-chain-length-polyhydroxyalkanoates using Bacillus australimaris isolated from groundnut oil mill dirt.

Abstract

The environmental burden of petroleum-based plastics has intensified interest in biodegradable alternatives such as polyhydroxyalkanoates (PHAs). This study reports the production of medium-chain-length PHAs (mcl-PHAs) using Bacillus australimaris isolated from groundnut oil mill dirt, an underexplored agro-industrial waste. The isolate was screened using Sudan Black B staining and identified via 16S rRNA gene sequencing. Cultivation in optimized mineral medium supplemented with lauric acid resulted in an average yield of 0.8033 g PHA per 5 g biomass, corresponding to 8.033 g/L volumetric yield. FTIR analysis confirmed the presence of key functional groups including carbonyl esters, while SEM revealed uneven surface morphology and a carbon-rich composition (98.86%). XRD patterns showed semi-crystalline characteristics, and TGA indicated thermal stability with major degradation occurring at 228.01°C. These results establish Bacillus australimaris as a promising candidate for mcl-PHA biosynthesis and highlight the utility of groundnut oil mill dirt as a microbial source. The findings support the development of cost-effective, biologically derived polymers for sustainable materials applications.