Biodegradability of polyethylene (PE), polypropylene (PP), and polystyrene (PS) microplastics by floc-forming bacteria, Bacillus cereus strain SHBF2 isolated from a commercial aquafarm

Abstract

The ubiquitous proximity of the commonly used microplastic (MP) particles particularly polyethylene (PE), polypropylene (PP), and polystyrene (PS) poses a serious threat to the environment, and human health globally. Biological treatment as an environment-friendly approach to MPs pollution has recent interest when the bio-agent has beneficial functions in their ecosystem. This study aimed to utilize beneficial floc-forming bacteria B. cereus SHBF2 isolated from an aquaculture farm in reducing the MPs particles (PE, PP, and PS) from their environment. The bacteria were inoculated for 60 days in a media containing MPs particles as a sole carbon source. On different days of incubation (DOI), the bacterial growth analysis was monitored and the MPs particles were harvested to examine their weight loss, surface changes, and alterations in chemical properties. After 60 DOI, the highest weight loss was recorded for PE, 6.87 ± 0.92%, which was further evaluated to daily reduction rate (k), 0.00118 gday− 1, and half-life (t1/2), 605.08 ± 138.52 days. The OD value (1.38 ± 0.18 Abs.) indicated the higher efficiency of bacteria for PE utilization, whereas the colony-forming unit showed the bacteria was growing at a higher rate while utilizing PP (1.04 × 1011 CFU/mL). Biofilm formation, erosions, cracks, and fragments were evident when the surface changes were observed using scanning electron microscopy (SEM) which resulted in the formation of carbonyl and alcohol group due to the oxidation and hydrolysis were confirmed using Fourier transform infrared spectroscopic (FTIR) analysis. The results confirmed and indicated a higher degree of biodegradation in all of the selected MPs types. Thus, this study revealed that the floc-forming bacteria, B. cereus SHBF2 has a high potential to be used as an effective MPs degrading bacteria.