Isolation and Enhancement of PHB-producing Bacteria from Sewage using Watermelon Rinds

Plastics contribute significantly to global environmental pollution due to their non-biodegradable nature. Biopolymers like polyhydroxybutyrate (PHB), synthesized by microorganisms, offer an eco-friendly alternative. This study reports the isolation and characterization of PHB-producing bacteria from untreated sewage, identifying one potent isolate as Bacillus tequilensis via 16S rRNA sequencing. Preliminary screening using Sudan Black B confirmed PHB accumulation. Optimization of growth conditions revealed that glucose and tryptone were the most effective carbon and nitrogen sources, respectively, yielding 0.10 g of PHB under optimal conditions (pH 7, 37 °C, 48 hours). Notably, substituting glucose with watermelon rind, a sustainable fruit waste, enhanced PHB production to 0.34 g, demonstrating a 3.4-fold increase. The extracted PHB was characterized using FT-IR, confirming the presence of functional groups typical of PHB. This study highlights a dual environmental benefit: valorization of sewage-derived bacteria and agro-industrial waste for sustainable bioplastic production. These findings present a novel approach for cost-effective and eco-friendly PHB synthesis.