Biodegradation of low-density polyethylene (LDPE) sheet by microalga, Uronema africanum Borge

Plastic (polyethylene) pollution is a severe cause of deterioration of a healthy environment. For example, ingestion of plastics in the animal gut, clogging of water canals and retarded solid waste management. Many conventional methods of polyethylene degradation include UV photooxidation, thermal oxidation, incineration, chemical oxidation and landfill are being practiced. However, these methods are not feasible, costlier and not a complete solution for this global issue. Therefore, plausible, alternative solution for this issue is biodegradation. Microbes such as bacteria, fungi and algae are involved in polyethylene degradation in its natural habitat. Among them, algae were given very less importance. In our present study, a potential microalga, morphologically identified as Uronema africanum Borge, isolated from a waste plastic bag collected from a domestic waste dumping site in a freshwater lake. This microalga was further treated with the LDPE sheet in BBM culture medium. Based on the results obtained from light microscopy, dark field microscopy, GC-MS, FT-IR, SEM and AFM, it was concluded that the microalga has initiated degradation of LDPE sheet within 30 days of incubation. Concurrently, the configuration of corrosions, abrasions, grooves and ridges were found similar with the morphological features of the microalga. For example, the configuration of the radial disc-like attachment structure of the microalga was found corresponding to the abrasions on the surface of LDPE sheet at an average size of 20-30 µm in diameter. Whereas, the configuration of ridges and grooves were found similar with the filamentous nature of the microalga (10-15 µm width). This is a hitherto report on the biodegradation of LDPE sheet by the microalga Uronema africanum Borge.