A current study by Dr. Başak Öztürk and her team at the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH in Braunschweig, Germany, investigated how marine organisms break down and utilise biologically degradable plastic. The researchers not only established the bacterial groups involved in the breakdown, but were also able to uncover a potential mechanism behind the degradation of the plastic material. The team recently published their findings in the internationally renowned journal Nature Communications (https://www.nature.com/articles/s41467-020-19583-2).
Plastic: an environmental issue
Demand for plastic has increased continuously over the last few years. For instance, in 2017 350 million tons of plastic were produced worldwide, more than 70 percent of which resurfaced as waste in the oceans. The industry has reacted to this increasing pollution of the environment by developing biologically degradable plastics. One frequently utilised material is poly(butylene adipate-co-terephthalate) (PBAT), which offers both the necessary mechanical properties as well as a good biologic degradability. PBAT is often used in packaging materials, bin bags and even in agriculture, for instance in mulch films, as its properties are very similar to those of the conventional plastic polyethylene (LD-PE). The breakdown of PBAT by microorganisms in the soil has already been extensively researched. However, it is still unclear how the breakdown occurs in an aquatic environment, and whether for instance marine bacteria would be able to use the degradation products as a food source.
Different bacteria cooperate when breaking down plastics
In their study, the research team was able to show that different bacteria from the groups Alphaproteobacteria, Gammaproteobacteria, Flavobacteria and Actinobacteria are involved in the degradation of PBAT. “Our first experiments demonstrated that a biofilm is formed on the plastic within the first three days; the first holes were apparent after six days”, reports Dr. Ingrid Meyer Cifuentes, postdoc researcher at the DSMZ and lead author of the publication. In total, it took the bacterial community 15 to 20 days to fully disintegrate the plastic material. During this time, the various bacteria used the metabolic PBAT products as carbon source for their own metabolism. The bacteria ultimately converted approximately 60 percent of the available plastic carbon into CO2.
Further experimental findings led the authors to conclude that the initial degradation of the plastic takes place within the biofilm. The resulting metabolic products are then further broken down by both the bacterial community of the biofilm as well as free-floating bacteria in the immediate surroundings. Thus, the degradation of the plastic is a synergistic feat. “The degradation process we investigated in the lab is probably a bit different to that in the ocean”, remarks microbiologist and study leader Başak Öztürk. “However, our findings clearly indicate that the degradation of plastic in a marine environment is similar to that observed in soil. In the long run, this knowledge could help science develop plastic with an even better organic degradability, and thereby make a significant contribution to the protection of the environment.”
Independent Junior Research Group “Microbial Biotechnology”
Dr. Öztürk has headed the Independent Junior Research Group “Microbial Biotechnology” at the Leibniz-Institute DSMZ since 2018. The group focuses on three main subjects: the investigation of the degradation, continuance and behaviour of biodegradable plastics in the marine ecosystem, the research of new microorganisms capable of breaking down groundwater-polluting pesticides and xenobiotics in the micromolar range, and the structural explanation of enzymes involved in these degradation processes.
Meyer-Cifuentes, I.E., Werner, J., Jehmlich, N. et al. Synergistic biodegradation of aromatic-aliphatic copolyester plastic by a marine microbial consortium. Nat Commun 11, 5790 (2020). doi.org/10.1038/s41467-020-19583-2
PhDr. Sven-David Müller, Head of Public Relations, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH
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About the Leibniz Institute DSMZ
The Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures is the world's most diverse collection of biological resources (bacteria, archaea, protists, yeasts, fungi, bacteriophages, plant viruses, genomic bacterial DNA as well as human and animal cell lines). Microorganisms and cell cultures are collected, investigated and archived at the DSMZ. As an institution of the Leibniz Association, the DSMZ with its extensive scientific services and biological resources has been a global partner for research, science and industry since 1969. The DSMZ is the first registered collection in Europe (Regulation (EU) No. 511/2014) and certified according to the quality standard ISO 9001:2015. As a patent depository, it offers the only possibility in Germany to deposit biological material in accordance with the requirements of the Budapest Treaty. In addition to scientific services, research is the second pillar of the DSMZ. The institute, located on the Science Campus Braunschweig-Süd, accommodates more than 73,000 cultures and biomaterials and has 198 employees. www.dsmz.de
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The Leibniz Association connects 96 independent research institutions that range in focus from the natural, engineering and environmental sciences via economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance. They conduct knowledge-driven and applied basic research, maintain scientific infrastructure and provide research-based services. The Leibniz Association identifies focus areas for knowledge transfer to policy-makers, academia, business and the public. Leibniz institutions collaborate intensively with universities – in the form of “Leibniz ScienceCampi” (thematic partnerships between university and non-university research institutes), for example – as well as with industry and other partners at home and abroad. They are subject to an independent evaluation procedure that is unparalleled in its transparency. Due to the importance of the institutions for the country as a whole, they are funded jointly by the Federation and the Länder, employing some 19,100 individuals, including 9,900 researchers. The entire budget of all the institutes is approximately 1,9 billion Euros. www.leibniz-gemeinschaft.de