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. • Rice straw hydrolysate effective valorization into bioplastic • C5 rich sugar to polyhydroxyalkanoate (PHA) production • Volatile Fatty Acids can be used as platform chemicals • Feast-Famine strategy efficiently directs microbes towards PHA accumulation