Valorization of agro-wastes for the biosynthesis and characterization of polyhydroxybutyrate by Bacillus sp. isolated from rice bran dumping yard.

Investigations have been made to determine the usage of inexpensive agro-waste products as an alternative carbon source for the production of degradable bacterial polyester. Among 33 bacterial isolates, a gram-positive bacterium PPECLRB-16 isolated from rice bran dumping yard was found to accumulate a relatively higher quantity of PHB and identified as Bacillus sp. through 16S rRNA gene sequence analysis. The higher PHB producing bacterial isolate was grown with different inexpensive agro-wastes to determine the suitable carbon source for its growth and PHB production. The one-factor-at-a-time approach comparatively enhanced PHB yield (5.64 g/L) when grown for 48 h with 1.5% (w/v) of defatted oil cake at a pH of 7.0. The bacterially accumulated PHB was isolated from the cells, purified, and characterized using solid-state 13C NMR, FT-IR, Powder XRD, TGA, GPC, Tensile and HR-SEM analyses. The hydrophobicity and printing accessibility of recovered PHB were demonstrated using contact angle measurement by coating on different surfaces. The results obtained in the present investigation have thrown light on the potential usage of agro-waste by-products, mainly oil cake, as an appropriate carbon source for the commercial production of PHB by Bacillus sp. in a cost-effective way. © King Abdulaziz City for Science and Technology 2021.