Isolation and Characterization of the Bioplastic Producing Bacteria Using Low-Cost Substrate, Sawdust

Abstract

Plastics are routinely used in the packaging of materials as well as in industrial production. However, once in the environment, they are non-biodegradable, posing severe threats to the ecosystems. Bioplastic replaces conventional plastic, which is biodegradable due to its biological origin and does not affect environment. Sawdust is a very important agrowaste screened as a substrate for bioplastic production. In the present study, bacteria capable of producing bioplastic by utilizing sawdust as a cheap substrate were isolated and optimized for bioplastic production. Eight sawdust utilizing bacteria were isolated and the strains were designated as SD1 to SD8. These indigenous bacterial isolates were screened for bioplastic production using Sudan Black B Staining. Among the bacterial isolates, the bioplastics (PHB) production levels were 0.046 g/mL to 0.32 g/mL, while the maximum PHB (g/ml) production (0.32 ± 0.008g/mL) was given by SD2 isolate identified as the Bacillus cereus-SD2 strain through 16SrDNA sequencing. The isolate SD2 was optimized for bioplastic production at different growth conditions. The best temperature for the bioplastic production was 37˚C in the saw dust containing low-cost medium and yielded 0.32 ± 0.00 optical density at wavelength 235 nm of crotonic acid. The isolate SD2 showed a higher PHB (g/ml) yield of 0.31 ± 0.008 under alkaline conditions of pH 9. Sufficient oxygen was required for the higher PHB (g/ml) production by the bacterial isolate SD2, which yielded a 0.32 ± 0.006 level of PHB as compared to the non-aeration. The Bacillus cereus-SD2 is a promising bacterial which can produce environmentally friendly bioplastics using low-cost substrate. Finding more growth condition for enhanced bioplastics yields in future are suggested to scale up the production process at industrial level.