Low-cost production of PHA using cashew apple (Anacardium occidentale L.) juice as potential substrate: optimization and characterization

Abstract

Polyhydroxyalkanoates are polyesters of R-hydroxyalkonic acids, prominently used as bioplastics on grounds of their complete biodegradable and environment-friendly characteristics. There is an upsurge in need of an alternative low-cost, renewable carbon source for the production of PHA for enhanced economic and to exert a positive impact on the industries. In the present work, cashew apple juice (CAJ) was supplemented as a carbon source for Cupriavidus necator to produce PHA. (NH4)2SO4, NH4Cl, NH4NO3 and CO(NH2)2, and NaNO3 were tested and urea was found to be the best nitrogen source that supports optimal growth of the microorganism. The production process was then optimized using response surface methodology by incorporating the effects of total reducing sugar concentration, urea concentration, and inoculum size. Under optimized condition, the resulting PHA yield was found to be 15.78 g/L with total reducing sugar concentration of 50 g/L, inoculum size of 50 mL/L, and urea concentration of 3 g/L. FT-IR, NMR, TGA, and DSC analysis revealed the product to be a copolymer of hydroxybutyrate and hydroxyvalerate.