In a promising development that could provide a solution to the menace posed by plastic waste, a scientist attached to the Malabar Botanical Garden and Institute for Plant Sciences (MBGIPS) in Kozhikode has isolated six strains of bacteria capable of breaking down plastic into biodegradable polymers.
The new strains were identified by the scientist R.B. Smitha from soil samples collected from a plastic recycling unit at West Hill, Kozhikode. The bacteria were found to produce polyhydroxyalkanoates (PHAs), a class of biodegradable polymers that could substitute synthetic plastics.
“In the presence of high carbon sources or nutrients like nitrogen, phosphorous, sulphur, oxygen, and magnesium, PHAs are synthesized by the bacteria as intracellular carbon and accumulate as granules in the cytoplasm, the jellylike material lining the inside of a cell,” explains Dr. Smitha. “All the six strains we identified were found to produce PHA granules.” Laboratory tests carried out at the MBGIPS and Calicut University revealed that plastic carry bags, blood bags, and plastic granules were completely degraded by the bacteria.
Biochemical tests and molecular analysis were used to identify the bacteria and confirm the production of PHA.
Six strainsThe six strains, namely Cronobacter muytjensii mbg5, C muytjensii mbg6, C sakazakii mbg1, C sakazakii mbg3, Enterobacter clocae mbg2 and Ohrobactrum intermedium mbg4, were submitted to the GenBank database on organisms and have been allotted accession numbers.
With properties similar to polyethylene and polypropylene, PHAs have emerged as an environment-friendly alternative to petrochemical-based plastic.
Many applicationsThey are finding applications as packaging and coating materials and production of medical equipment like blood bags and surgical sutures.
Dr. Smitha said the bacteria were found to produce 80 to 85 per cent more of PHA when fed on biomass like water weeds that choke canals and lakes in Kerala.
“We have stumbled on something that has the potential to solve the twin menace of water weeds and plastic that the State is struggling to contain,” observes R. Prakashkumar, Director, MBGIPS. He, however, stresses the need for a major initiative to scale up the work at different levels and make it a viable project.
Last year, Dr. Smitha had reported the discovery of three strains of oil degrading bacteria. “Efforts are on to isolate and purify the key hydrocarbon- degrading enzyme produced by the bacteria and patent it,” she said.
