Yeast breaks down biodegradable plastic, researchers find.
A boy sorts through empty plastic bottles at a recyclables shop in Quetta, Pakistan on Nov. 15. The plastic bottles are not biodegradable, but Japanese researchers identified a common yeast strain that breaks down biodegradable plastics. Naseer Ahmed/ REUTERS

Across Tsukuba, 45 miles north of Tokyo, plastic mulchfilms spread across fields of hakusai cabbage and daikon radishes, keeping the vegetable crops weed-free and the drip-irrigated soil moist.

Each year after harvest, farmers need to dispose thousands to millions of acres of the plastic, creating a huge amount of labor and environmental headaches.

Biodegradable plastics could be useful, but the degradation process can be irregular because of the weather so farmers can't depend on the plastic being eaten away when the next crop season arises.

A Japanese research group identified the yeast strain Pseudozyma, common worldwide, that excretes an enzyme that eats away at biodegradable plastics, giving a potential tool in a vegetable farmer's arsenal.

However, researchers expect the plastic-eating enzyme could be useful outside vegetable fields and help accelerate degradation of biodegradable plastics around the house and office.

If we can degrade plastics immediately after use, it will change the way of plastics use, Hiroko Kitamoto, researcher at the National Institute for Agro-Environmental Sciences in Tsukuba, Japan and lead author, wrote in an email.

The journal AMB Express published the study online Tuesday.

Some critics say that biodegradable plastics may be good in theory, but in practice, any garbage-bound plastic will not degrade in an airtight landfill.

The issue of kickstarting degradation of biodegradable plastics degrade will become more significant in the future as the industry grow.

A market report released Monday estimated that the global market value of biodegradable plastics will reach $1.85 billion by 2011, a market that is expected to increase over the next 10 years. Visiongain, a market analyst firm based in London, UK released the study.

Biodegradable plastics are made from complex sugars such as poly-butylene succinate that currently three microbes are known to degrade into carbon dioxide and water.

Those plastics differ from photodegradable plastics where a light-sensitive chemical binds together tiny pieces of plastic. Small pieces of plastics are remained after degradation of photodegradable binder, Kitamoto wrote. It will be the problem of the plastic pollution.

The research group is keeping mum on the identity of the enzyme other than writing about its size. We are writing about it in the next manuscript, Kitamoto wrote.