doi:10.1038/nindia.2013.170 Published online 17 December 2013
Researchers have identified three marine bacteria that can degrade polyethylene, a polymer widely used to make plastic products . These marine bacteria could be used as an ecofriendly way to degrade plastic products in the environment.
Every year India uses 8 million tons of plastic products, some of which end up polluting marine environments. Plastic products are non-degradable and hence harmful to various animals, such as fish, birds and marine animals. Microbial degradation of plastic is a potential solution.
To identify new microbes that can degrade plastic, the researchers cultivated 60 species of marine bacteria on low-density polyethylene films isolated from pieces of polyethylene bags. Three of these bacteria — Kocuria palustris, Bacillus pumilus and Bacillus subtilis — utilized polyethylene as their sole source of carbon and energy. The researchers then investigated the ability of these bacteria to attach to and degrade polyethylene films.
The bacteria showed increased respiration rate and metabolic activity, indicating that they were growing on the polyethylene films. The study detected the activity of dehydrogenases, a group of intracellular enzymes involved in microbial metabolism.
The metabolic activity of the polyethylene bacteria attached to the films caused the films to degrade. This degradation was evident in the dry weight loss of the polyethylene films: after 30 days of incubation with the films, K. palustris, B. pumilus and B. subtilis reduced the film weight by 1, 1.5 and 1.75 per cent, respectively.
"This study provides experimental evidence that these marine bacteria are capable of degrading plastic without any physical or chemical treatment," says B. Jha, a senior author of the study.