Biodegradation Potential of Mixed Cultures of Bacillus sp. and Priestia sp. from Landfill Investigated on Low-Density Polyethylene (LDPE) Sheets

Abstract This study investigated the efficacy of mixed cultures of Bacillus sp. (isolate BS5) (accession no. OP536168) and Priestia sp. (isolate TL1) (accession no. OP536170) in degrading low-density polyethylene (LDPE) sheets derived from synthetic plastic source (Ziploc bags). The mixed culture was compared against single isolate application over a 48-day period. Biodegradation was confirmed by weight loss and the changes to the surface of the LDPE sheets. Biofilm production, bacterial growth, and esterase production was also quantified to describe biodegradation of LDPE. Results revealed that application of Bacillus sp. (isolate BS5) and Priestia sp. (isolate TL1) as mixed cultures were generally more effective in degrading LDPE. A gradual increase in weight loss, reaching 0.667% by day 48, was observed, along with biofilm production (0.099 at OD 550 ), growth (0.261 at OD 600 ), and esterase production (0.0028 U/mL). The effectiveness of the mixed cultures was attributed to the function of isolate Bacillus sp. (isolate BS5), which on its own (application as single isolate), demonstrated relatively high levels of biofilm production (0.089 at OD 550 ), growth (0.337 at OD 600 ), and esterase activity (0.00033 U/mL), that led to a weight loss of 0.467% of the LDPE sheets. The Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) showed LDPE sheets undergoing early signs of degradation with surface damage (pits and perforations), bacterial colonization, and biofilm formation observed on surface of LDPE sheets. These results established the potential of the bacterial isolates in degrading synthetic LDPE and corroborated the prospects of mixed bacterial culture application to achieve better results.