Pune, May 1st 2019
(India Science Wire): Fungi are said to be grand recyclers of the planet and are
considered vanguard species in habitat restoration. Now Indian scientists have
found that they may also be the answer to one of the biggest environmental
problems – plastic pollution. They have identified fungi which can potentially
help degrade polythene.
By Amruta Morone
Researchers led by Dr. Avinash Ade at
Savitribai Phule Pune University have identified certain fungi with high
polythene degradation potential from mangrove rhizosphere soil (root soil where
microorganisms colonise) collected from 12 different locations in five coastal
states – Kerala, Karnataka, Maharashtra, Goa and Gujarat. These locations were
plastic waste dumping sites with growing mangroves surrounded by marine water.
Polythene contributes around 64% of
the total plastic waste and takes about 1000 years to degrade under natural
environmental conditions. Despite a ban, single-use polythene bags are still
being used widely and are accumulating at dumping sites. Available options for
polythene disposal such as incineration are harmful to the environment. Biodegradation
or degradation using microbes is considered suitable and eco-friendly. That’s
why scientists have been hunting for microbes capable of degrading polythene.
From the soil samples collected
from coastal areas, fungi were isolated in the laboratory and subjected to
analysis. “Among the 109 fungal isolates that we obtained, Aspergillus
terreus strain MANGF1/WL and Aspergillus sydowii strain PNPF15/TS have
been found to be the most efficient polythene degraders,” said Dr. Ade, while
speaking to India Science Wire. “These isolates are much more efficient
than those reported from other parts of the world,” he added.
Polythene strips were placed in petri
dishes containing fungi and were subjected to regular shaking at room
temperature. Primarily, reduction in weight and tensile strength of polythene
after this period was chosen as a criterion for assessing degradation
efficiency of the fungi. Aspergillus terreus strain MANGF1/WL showed about
50 % weight loss of polythene while Aspergillus sydowii strain PNPF15/TS
showed a 94 % reduction in tensile strength of polythene.
After screening, the most efficient
polythene degrading fungi were analysed using Scanning Electron Microscopy and
Fourier-transform infrared spectroscopy (FTIR) to confirm the level of
polythene degradation. Researchers also investigated products obtained from
polythene degradation. “We studied the harmful effects of these products on
tiger shark fish and sorghum seeds and found them to be least toxic to both,”
said Dr. Ade.
However, the mechanism of degradation is not yet known. “We are seeking to get an insight into the enzymes acting upon polythene and genes involved in its degradation. We are also exploring other fungi for degradation of another plastic, polyvinyl chloride,” he further informed. The researchers have published their findings in the journal Scientific Reports. Besides Dr. Ade, the research team included Dr. Manisha Sangale (Savitribai Phule Pune University) and Dr. Mohd Shahnawaz (currently with CSIR-Indian Institute of Integrative Medicine, Jammu).