Bioconversion of agro-industrial effluents for polyhydroxyalkanoates production using Bacillus subtilis RS1

The effectiveness of inexpensive agro-industrial wastes such as sugarcane molasses, paper mill effluent, and dairy effluent for the production of polyhydroxyalkanoates (PHAs) using Bacillus subtilis RS1 was assessed in this study. Laboratory-scale fermentations were carried out with both raw and pre-treated agro-industrial effluents, and maximum PHAs yield was observed in pre-treated effluents. Experimental variables such as pH, inoculum dose, and incubation time were further optimized to maximize PHAs yield, and the optimal conditions were identified as incubation time 48 h; pH 7; and inoculum dose 10% v/v. PHAs yield in pre-treated sugarcane molasses increased to 70.5% under optimal conditions. Fourier transform infrared spectroscopy and gas chromatography–mass spectrometric analysis revealed that the extracted polymer was composed of penta- and hexadecanoic acid methyl esters, a copolymer of PHAs. Results indicated that the pre-treated sugarcane molasses could be used as an inexpensive substrate for the production of PHAs.