Marine bacterial based enzymatic degradation of low-density polyethylene (LDPE) plastic

Abstract

Polyethylene has become an essential part of the day-to-day activities of human life. However, its excess use led to accumulation in the environment-causing marine pollution without having any safe and proper disposable methods. Biodegradation is the most efficient method to control synthetic plastic waste pollution sustainably. In the present study, we used three identified marine bacterial isolates (two Marinobacter sp. (H-244 and H-246) and one Bacillus subtilis (H-248)) to degrade unplasticized low-density polyethylene film after screening and showed maximum weight loss up to 1.68% by H-246 bacterial isolate within 90 days. The degradation of LDPE film by bacteria was characterized by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) analysis for topographical changes such as crack, pits, cavity and roughness. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) analysis of degraded film showed the addition of extra-functional group at the range of 1025–1275 cm−1 with an increase in C-O stretching that is due to the addition of alcohol (–OH) group, which was further confirmed by the gas chromatography-mass spectrometry (GC-MS) analysis of degraded by-products release of fatty acids due to esterase activity. A decrease in tensile strength (0.43 MPa) and thermal weight loss (99.63%) in LDPE degraded by bacterial isolate H-246. Carbon content was also reduced in the bacterial degraded LDPE film from 86.10% to 80.45% for bacterial isolate H-244. All these characteristic changes in polyethylene were occurred due to esterase enzyme production by the bacteria and confirmed by isolation and purification, which showed 32, 32 and 43 KD of molecular weight for bacterial isolate H-244, H-246 and H-248, respectively. The present study of LDPE biodegradation by three marine bacteria has acted as a suitable candidate and will help in decreasing plastic waste.