Bacteria that breaks down plastic bags

OK, I’ve written about a terrifying burden on the environment that is plastic bags. Now a Canadian high school student may find a plausible solution to this problem — by isolating bacteria that break down plastic bags in 3 months, instead of millions of years.

Daniel Burd, a 16-year-old student of Waterloo Collegiate Institute decided to do something about the pile of plastic bags that was sitting in his closet. He knew that plastic bags do eventually degrade, and that microorganisms could be behind it. But the degrading microbes are difficult to isolate because they do not exist in high numbers in nature.

To find out which bacteria are more effective as biodegraders, he put together a bacterial culture medium by mixing some household chemicals, tap water and yeast. He ground plastic bags into a powder and added it to the medium along with some dirt. The mixture was placed in a shaker at 30 degree for 3 months. Then he filtered out the remaining powder, transfer the culture into 3 flasks and also prepared a flask of boiled culture as the negative control. He placed strips of plastics cut out from bags into these flasks and compared the weights of the plastic strips after 6 weeks. He observed a 17% decrease, but that’s not good enough for him.

To identify the specific strain of bacteria responsible for degrading the plastic, Daniel grew the microbes on agar plates and found 4 different species. He did more tests using plastic strips and found that only the second strain was able to break down the plastic significantly.

Growing the strain with the others respectively indicated that the first strain and the second strain together resulted in 32% weight loss in plastic strips. Daniel hypothesized that strain no. 1 helped strain no. 2 reproduce. More tests revealed that the degrading species was Sphingomonas bacteria and the helper was Pseudomonas.

He did more tests using different bacterial concentrations, temperatures, and addition of sodium acetate as a carbon source for the bacteria. He found that at 37 degrees, with the optimal concentration and a little sodium acetate added, 43% degradation was achieved in 6 weeks. Although he did not actually do the test, but the plastic strips should be totally broken down in double that time. He also checked whether this could work on a larger scale by testing whole plastic bags. It worked, too.

A researcher in Ireland had shown that Pseudomonas broke down polystyrene, but Daniel Burd was the first to reasearch on polyethelene plastic bags.

There should not be any problem applying this method in the industry, all that is required includes a fermenter, a bacterial growth medium, the bugs and the plastic bags. Since the bacteria also produce heat during the process, little energy is needed to maintain the optimal temperature. The system produces only water and carbon dioxide, in the minuscular amount of 0.01% of the bacteria’s weight. If this works, it is a huge step forward in solving the problem of “white pollution.”

And all this coming from a 16-year-old teenager with an idea to do something that most of us just accept as it is. Now that’s the power of science!

Source: WCI student isolates microbe that lunches on plastic bags

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