Development of an Integrated Biorefinery System for Bioconversion of Lignocellulosic Biomass to Polyhydroxyalkanoates and Biohydrogen

Abstract

A sustainable lignocellulosic biomass-based biorefinery requires complete utilization and valorization of the biomass components. In the present study, a phase-separated pretreatment (chemo mechanical─delignification followed by bacterial pretreatment) was performed to fractionate lignin and cellulose-rich residue from rice straw biomass (RSB) to utilize lignin for polyhydroxyalkanoates (PHA) and cellulose-rich residue for biohydrogen production. A higher lignin removal of 81.4% was obtained through combined H2O2–homogenizer pretreatment. The lignin was utilized as a substrate by Bacillus cereus for PHA production. The cellulose-rich delignified RSB was hydrolyzed with cellulase-secreting bacteria. A higher chemical oxygen demand solubilization of 38.2% was achieved in delignified and bacterially (Delig-Bac) pretreated RSB than bacterially pretreated (Bac) alone (22.9%) and control (3.43%). A higher cellulose solubilization of 35.8% was obtained in Delig-Bac pretreated RSB than Bac alone (21.5%). A higher PHA concentration, content, and yield of 480 mg/L, 56%, and 561 mg/g were obtained from 2.970 g/L of lignin. Higher biohydrogen production of 66 mL/gVS was achieved in Delig-Bac pretreated RSB. The economic analysis revealed that Delig-Bac was found to be economically feasible with a net profit of 4.18 USD/m3 when compared to Bac (−457.4 USD/m3).