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Osaka Univ. research team developing starch compound to break down marine plastics

The degradable plastic being developed by a team led by Osaka University graduate school professor Hiroshi Uyama is seen in bag and stick shapes, on Nov. 9, 2020, in Kita Ward, Osaka. (Mainichi/Koki Matsumoto)

TOKYO -- A team of scientists at Osaka University is working on creating plastic using the common food ingredient starch to solve the global problem of marine plastics derived from used plastics including bottles, bags and straws that find their way into our oceans, which are threatening the environment and organisms in our seas.

    A group led by polymer material chemistry professor Hiroshi Uyama at the Graduate School of Engineering Osaka University has partnered with around 30 private companies in an attempt to find a solution that could make plastics in our seas return safely to nature.

    According to organizations including Japan's Ministry of the Environment, each year the world produces some 400 million metric tons of plastic, and 8 million tons of it enters our oceans. Most of these items are semi-permanent and don't break down and remain as they are in the environment. But, they present a serious danger to life, including by contributing to changes turning the sea bed into sludge. Large amounts of plastic trash have also been found in the digestive systems of whales, seabirds and other creatures fished from the oceans.

    Professor Uyama and others announced in March 2020 that they developed a material stronger than existing plastics which could break down in the sea. According to Uyama, there have been other decomposing plastics before, but they come at a high cost that precludes their mass production, and many such products only decompose on land.

    The key point of the plastic they're developing is that starch has been mixed in with the plant fiber cellulose for it. On dry land, it maintains good decomposability and is easily processed, meaning it could lead to a fall in costs for the material.

    But why will it help with decomposition under the sea? Starch is made up of alpha-glucose bound together in a large number to form the carbohydrate. For many microorganisms floating around in the oceans, these compounds are delicious. As a result, the surface of the starch-made plastic is mobbed by microorganisms, which create a sheet-like bio film. The organisms release an enzyme called amylase, which unpacks the sugar molecules and breaks down starch to extract it as nutrients. Additionally, the microorganisms reportedly also release enzymes which breakdown protein and fat, meaning that they can dissolve plastic components other than starch.

    The research quickly made waves in the manufacturing industry. From September onward, the team started recruiting private companies to participate in an academic-industrial collaboration to develop the concept. Among the firms that offered their services are material processing makers, chemistry-related companies, food manufacturers, retailers and others. By Nov. 9, 25 commercial firms and research bodies had joined the project.

    The team says they're considering testing the mixture on food packaging and other products, and that it has already been successfully produced in bag and stick shapes. They will be looking into more concrete uses for the product, and aim to exhibit it at the 2025 World Exposition in Osaka, Kansai.

    At present, the research is at the stage where tests are being done to confirm whether substances other than cellulose can be broken down when combined with starch. Professor Uyama said, "We've had many more companies come on board than we had imagined. We won't be able to solve all the world's marine plastic problems with these substances, but by using familiar ingredients like starch, we can bring costs down, increase interest, and move little by little toward changing the environment."

    (Japanese original by Koki Matsumoto, Science & Environment News Department)

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