A Study on the Synthesis of Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) by Bacillus megaterium Utilizing Cheese Whey Permeate

Cheese whey permeate, a processed by-product of the dairy industry, was utilized as the sole carbon source for the production of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from Bacillus megaterium. In the present study, propionic acid was co-fed as an internal plasticizer to synthesize PHBV co-polymer. Cultivation parameters such as time, propionic acid, C/N ratio were optimized by investigating several parameters that affect the production of PHBV. The maximum PHBV content of 86.6% and the highest PHBV yield of 3.64 g/L were achieved at 72 h, 0.1% propionic acid content, and C/N ratio of 15. The presence of PHBV in the extracted sample was confirmed by gas chromatography-mass spectroscopy (GC-MS) and Fourier transform-infrared spectroscopy analysis, and further, the morphology was studied by scanning electron microscopy analysis. Mechanical characterization revealed that PHBV has a tensile strength of 4.41 MPa, which was higher than polyhydroxybutyrate with 3.37 MPa. The PHBV biopolymer was observed to be thermally stable between 100-400 degrees C. The melting point, crystallization temperature and glass transition temperature of PHBV were measured to be 116.60 degrees C, 108.92 degrees C and 87.88 degrees C respectively. The synthesized PHBV nanoparticles had an average diameter of 343.3 nm, and the zeta potential was found to be-21.3 mV.