Rice straw hydrolysate valorization for efficient polyhydroxyalkanoate production in a two-stage process

Lignocellulose hydrolysate bioconversion into Polyhydroxyalkanoates (PHAs) has emerged as a captivating alternative to petroleum-based polymers. The present work investigated PHA biosynthesis from a volatile fatty acids (VFAs)-rich titer produced from anaerobic digestion of C5-sugar rich rice straw hydrolysate (RSH). The feast and famine approach employed for PHA production produced 9.207 g COD/L PHA during famine cycle 5, resulting in a PHA yield of 0.11 g PHA/g dry rice straw. Famine conditions selectively induce stress and allow only stress-tolerant organisms to survive. The microbial community population during the maximum PHA production was dominated by genera Acinetobacter Paenibacillus, Bacillus, and Lysinibacillus. The produced PHA was analyzed by NMR and FTIR and found to be a copolymer Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) combination of ∼55 % hydroxybutyrate (HB) and ∼45 % hydroxyvalerate. Biodegradable and biocompatible plastic products made from this PHA combination can be used in a variety of applications, including biotechnology, food packaging, and medical equipment.