University of Tübingen: Cyanobacteria could revolutionize the plastics industry

As a by-product of photosynthesis, cyanobacteria produce plastic on a natural basis – sustainably and environmentally friendly. Researchers at the University of Tübingen have now succeeded for the first time in changing the metabolism of bacteria in such a way that they produce the natural substance in quantities that enable industrial use. The natural plastic could compete with the environmentally harmful petroleum-based plastic. The research group, led by Professor Karl Forchhammer from the Interfaculty Institute for Microbiology and Infection Medicine, recently presented its results in several studies that appeared in the journals Microbial Cell Factories and PNAS .

“The industrial relevance of this form of bioplastic can hardly be overestimated,” said Forchhammer. Around 370 million tons of plastics are currently produced each year. According to forecasts, global plastic production will increase by another 40 percent over the next decade. Plastic can be used in a variety of ways and is inexpensive, for example as food packaging. On the other hand, it is the cause of increasing environmental problems. More and more plastic waste ends up in nature, where the plastics partly pollute the oceans or end up in the food chain in the form of microplastics. In addition, plastic is mainly made from crude oil, which releases additional CO2 into the atmosphere when it is burned.

A solution to these problems could be found in a strain of cyanobacteria with surprising properties. Cyanobacteria of the genus Synechocystis produce polyhydroxybutyrate (PHB), a natural form of plastic. PHB can be used in a similar way to the plastic polypropylene, but is quickly degradable in the environment and free of harmful substances. However, the amount produced by these bacteria is usually very small. The Tübingen research group succeeded in identifying a protein in the bacteria that restricts the carbon flow in the direction of the PHB within the bacterial cell. After removing the corresponding regulator and making other genetic changes, the amount of PHB produced by the bacteria increased enormously and ultimately made up over 80 percent of the total mass of the cell. “We created real plastic bacteria,” says Dr. Moritz Koch, first author of the study published in Microbial Cell Factories.

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