Challenges of exopolysaccharides production from polystyrene degradation by bacterium CHB 1.5 strain

Polystyrene (PS), a substance that constitutes a significant portion of plastic waste, has resulted in environmental pollution and adverse health effects. Biodegradation and chemical transformation of PS are limited. However, biodegradation is one alternative way to reduce plastic pollution. This research aims to select plastic-degrading bacteria and produce exopolysaccharides (EPS) from plastic waste. Among the marine plastic waste at Chala tat Beach (Songkhla, Thailand), 35 rod-shaped and Gram-positive bacteria were found. The selected strains that exhibited the highest optical density (OD) at 600 nm were CHB1.5, CHD2.2, and CHC3.2. The efficiency of EPS production was tested and showed that CHB 1.5 could produce the maximum amount of EPS (13.47 +/- 0.10 g/L) with a significant difference. After four weeks of plastic breakdown, CHB 1.5 had the highest total count (4.03 +/- 0.02 Log CFU/mL), followed by CHD2.2 and CHC3.2 (3.99 +/- 0.12 and 3.96 +/- 0.02 Log CFU/mL, respectively). CHB 1.5 was also examined to use PS foam as a carbon source in modified Mineral Salt Medium for EPS production, with an EPS yield of 1.36 +/- 0.08 g/L in week 4. The presence of amides I, polysaccharides, benzene rings, and hydroxyl groups (O-H) was detected by Fourier transform infrared spectroscopy. The Scanning Electron Microscope images confirmed the adherence of the CHB1.5 strain and EPS formation on the plastic sheet. In conclusion, the strain CHB1.5 showed promising potential for degrading PS plastic and producing EPS. Its qualities could be utilized in the future, as well as contribute to the reduction of plastic pollution in the environment in an eco-friendly way.