Production and Characterization of Polyhydroxyalkanoates from Food Waste Using Indigenous Bacterial Strains

Abstract

The accumulation of petrochemical plastics necessitates sustainable alternatives. This study investigated the production of polyhydroxyalkanoates (PHAs) using indigenous bacterial strains isolated from Balochistan's soils and five locally sourced food wastes: rice bran, potato peels, fruit pulp, dairy waste, and corn starch. The isolates were identified as Bacillus megaterium and Cupriavidusnecator via 16S rRNA sequencing. Fermentation parameters were systematically optimized for each strain. C. necator achieved a maximum PHA yield of 4.5 ± 0.3 g/L, constituting 85% of the cell dry weight, using Rice Bran at 30°C, pH 7.0, and 1% NaCl. Hydrothermal pretreatment increased yields by up to 36%, and nitrogen limitation enhanced polymer accumulation by 40-50%. Characterization by FTIR, NMR, and GC confirmed the synthesis of poly(3-hydroxybutyrate) (PHB) by B. megaterium and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with up to 33% hydroxyvalerate by C. necator. The PHBV copolymer exhibited a tensile strength of 32-40 MPa and a degradation temperature of 248-268°C, properties comparable to polypropylene. These results demonstrate that indigenous Balochistan strains efficiently convert regional food wastes into bioplastics with competitive material properties, establishing viable substrate-specific and strain-dependent bioprocessing strategy.