Tuning enzyme concentration and particle size for LDPE biodegradation using lipase and laccase systems

The persistent accumulation of low-density polyethylene (LDPE) waste in the environment has necessitated the exploration of eco-friendly degradation methods. This study aimed to degrade LDPE films using lipase (Lip) and laccase (Lac) enzymes obtained from Aspergillus flavus. The effects of enzyme concentration and LDPE particle size on the degradation rate were examined. LDPE samples were prepared in three particle sizes: 0.5, 1, and 2 cm. These samples were incubated with Lip, Lac, and a combination of both enzymes (Lip-Lac) at two concentration levels: 50% and 100% (v/v). The degradation process or extent of degradation was monitored over 10 and 30 days by analyzing percentage weight loss and observing surface morphology using scanning electron microscopy (SEM). Results indicated that the highest degradation occurred in the Lip-Lac system with 0.5 cm particles at 100% enzyme concentration, yielding a weight loss of 23.81% after 30 days, thereby suggesting that the blend performed better than the single enzyme system. SEM analysis confirmed extensive surface erosion and cracking in smaller particles treated at higher enzyme concentrations. This study also demonstrated that both enzyme concentration and LDPE particle size significantly influence biodegradation efficiency. Taken together, the bifunctional enzyme system is an efficient treatment method for enhancing the degradation process of plastics such as LDPE.