Isolation and characterization of low-density polyethylene degrading and biosurfactant-producing bacteria from soils

Abstract

Microorganisms play a very important role in the biological decomposition of various materials in the natural environment, this is called biodegradation. Synthetic materials including plastic and polyethylene waste accumulate in the environment and pose an ever-increasing ecological threat to humankind and the overall ecosystem on earth. Biodegradation of these plastic wastes using potent microbial strains could provide a solution to the problem. In the present study, the microorganisms responsible for biodegradation were isolated and characterized from local samples contaminated with hydrocarbon polymers. The experiment was conducted over a series of screening methods. The primary screening involved culturing collected samples for over 40 days to screen out low-density polyethylene (LDPE) non-degrading bacteria, followed by observation of polyethylene glycol (PEG) utilization by the formation of a clear zone. This led to the isolation of 43 different colonies. Secondary screening further allowed for selection of 14 different isolates that were able to form biofilm over the polymer surface. Finally, the tertiary screening allowed for the selection of 10 different isolates that are confirmed LDPE-degraders. From continuous culturing for 36 days, 8 out of 10 isolates were able to survive and propagate in minimal salt broth, namely, Staphylococcus sp., Acinetobacter sp., Clostridium sp., Bacillus sp., and Lysinibacillus sp. Finally, organism able to produce anionic and cationic biosurfactant were identified as Clostridium novyitype A and Staphylococcus massiliensis respectively.