Here, there and everywhere—the omnipresence of discarded plastic bags, in spite of the many bans, cannot be ignored. The convenience these polythene bags offer for packaging has popped up the production of polythene, accounting for 35% of total plastic production. Consequently, they also constitute nearly 64% of plastic waste, ending up on our land and in our oceans, choking many animals to death and clogging our drains. The findings of a recent study by researchers at the Savitribai Phule Pune University may put an end to this plastic menace. The researchers have identified a fungal strain that can degrade polythene—the most common form of plastic.
Many attempts have been made to degrade polythene, including irradiation using gamma rays and treatment with reactive chemicals. However, these methods result in more harmful effects by producing toxic end-products which worsen the problem. Biodegradation, or degradation using microbes, is considered to be an eco-friendly approach to manage plastics. Scientists across the globe are on the lookout for some bacteria or fungi that can degrade polythene, which is made up of organic and inorganic compounds.
In the current study, researchers have identified two strains of fungi, Aspergillus terreus and Aspergillus sydowii, which can degrade polythene under laboratory conditions. The findings of the study are published in the journal Scientific Reports. The study was partially funded by the University Grants Commission (UGC) and the Science Engineering and Research Board (SERB).
The researchers searched about 109 strains of fungi, found in heaps of plastic dumped on mangrove soil, from 12 various eco-geographical locations on the west coast of India. They tried to identify possible strains that can degrade polythene, zeroing on two of them—Aspergillus terreus and Aspergillus sydowii—as potential candidates. When they grew these two fungi on polythene strips in a laboratory, the researchers observed a reduction in the weight, tensile strength, elongating nature of polythene, indicating degradation. A look at the surface of these strips under an electron microscope confirmed the action of these fungi.
“By measuring the tensile strength of the treated polythene strips with fungi from mangrove rhizosphere, the polythene degradation was compared. In our case, 94% tensile strength reduction was observed. This study is the first of its kind to achieve such a tensile strength reduction in polythene using fungi”, says Dr Avinash Ade, an author of the study.
Apart from their innate ability to degrade polythene, the media in which they grow, its pH and temperature also play a role in enhancing the process. In the present study, these conditions were optimized, and the researchers achieved about 50% loss in the total weight of polyethene strips.
The researchers say that since these fungal strains can be grown under lab conditions, they could be used in dump sites that are rich in polythene. “As a next step, we are working on extracting and isolating enzymes from these fungi that are responsible for degrading polythene and other forms of polymers”, says Dr Ade.
In a world that produces 9.2 billion tons of plastic per year, of which 6.9 billion tons is discarded as 'waste', innovations like these are the need of the hour.