Accelerated degradation of low-density polyethylene by bacteria isolates: Insights from Surabaya River, Indonesia

Low-density polyethylene (LDPE) plastic bags were the dominant type of waste in Surabaya River, accounting for 21.16 particles/m³ in 2021. For both the environment and human health, LDPE poses a significant risk, as it contains plastic additives (plasticizers) with the ability to bind heavy metals such as copper (Cu), zinc (Zn), nickel (Ni), and lead (Pb). Therefore, this study aimed to compare the plastic degradation abilities of different bacteria isolates in the Surabaya River. Analysis was carried out to explore bacteria growth on plastic surfaces, changes in the chemical structure of the plastic, and the morphological variations of the plastic surface over a 30-day incubation period. Bacteria isolates were collected from a depth of 1.5 meters in the Surabaya River. The results showed that M2 had the highest bacteria growth on the plastic surface, reaching 42×10⁴ cfu/mL. Additionally, isolates M2, M3, and M4 were able to stretch the plastic’s chemical structure affecting O-H, C-H, C=C, and C-O groups, thereby causing visible damage to the plastic surface. The 16S RNA sequencing identified isolates M2, M3, and M4 as Bacillus cereus and Pseudomonas sihuiensis. Based on bacteria growth, changes in the plastic chemical structure, and surface damage, the results suggested that Bacillus cereus was more effective in degrading plastic than Pseudomonas sihuiensis.