PRODUCTION OF POLYHDROXYALKANOATE USING AGRICULTURAL WASTES BY LOCALLY ISOLATED STENOTROPHOMONAS MALTOPHILIA

Polyhydroxyalkanoates (PHAs) are biodegradable microbial polymers with potentials as alternatives to petroleum-based plastics; however, the cost of conventional carbon substrates remains a major limitation to their production. This study investigated PHA production by a locally isolated Stenotrophomonas maltophilia using agricultural wastes as alternative carbon sources. Soil samples were serially diluted and were used for the isolation of bacterial colonies on nutrient agar enriched with glucose. Potential PHA-accumulating bacteria were identified through staining Sudan Black B, which revealed fluorescent or dark-stained intracellular granules under microscopy confirming PHA synthesis potential upon nutrient depletion. Positive isolates from preliminary screenings were further subjected to PHA production studies under standard laboratory conditions. Five bacterial isolates were obtained from contaminated soil and screened for PHA accumulation, after which isolate A4 was selected and identified by 16S rRNA gene sequencing as S. maltophilia. Pretreated sugarcane bagasse, banana peels and rice rusk were evaluated for reducing sugar release and PHA production. Sugarcane bagasse produced the highest reducing sugar concentration (0.7414 mg/mL), followed by banana peels (0.3176 mg/mL) and rice husk (0.0228 mg/mL). Correspondingly, PHA yields were 53.7%, 33.3% and 16.6% respectively. The findings demonstrate that sugarcane bagasse is a promising low-cost carbon source for PHA production by S. maltophilia and provide a basis for further optimization, characterizations and scale-up studies.