Hokkaido University of Science

A bacterium found in the sea can degrade a plastic that otherwise resists microbial breakdown in marine environments. A bacterium found in the sea can degrade a plastic that otherwise resists microbial breakdown in marine environments. A bacterium that can degrade the common polymer polybutylene succinate (PBS), which naturally biodegrades to only a limited extent in marine environments, could lead to improved ways to recycle this polymer. The bacterium's potential, and its enzyme molecule that breaks down PBS, was discovered by researchers at Hokkaido University, working with colleagues at the Mitsubishi Chemical Group in Japan. The team published their results in the journal Environmental Microbiology. PBS is generally regarded as an eco-friendly polymer due to its biodegradability when discarded on land and exposed to the atmosphere. This has led to its increasing use since the early 1990s in industrial plastics, including mulching films, compostable bags and catering packaging. But many discarded plastics eventually find their way into the sea, and unfortunately PBS does not biodegrade well in that environment. "Plastic pollution in the ocean is a global problem and we need to tackle it by gaining new understanding of plastic behaviour in that environment, and new technologies to deal with the pollution," says Tomoo Sawabe, leader of the research team at Hokkaido University's Faculty of Fisheries Sciences. As only a small number of marine microorganisms able to biodegrade PBS had been discovered previously, Sawabe and his colleagues set out to try to find others and with better activity. They examined the effect on PBS of microbes gathered from natural seawater off Japan, allowing them to identify several types of marine bacteria that could degrade it. They also identified the enzyme responsible for degrading PBS in a specific strain of bacteria called Vibrio ruber. They named the enzyme PBSase. They then took things further by using molecular biological techniques to insert the gene for PBSase into the common bacterium Escherichia coli, which they cultured to produce highly purified samples of the enzyme for further study. "Elucidating the degradation mechanism in seawater at the molecular level may lead to the development of new marine biodegradable polymers," says Yasuhito Yamamoto, Sawabe's collaborator at Mitsubishi Chemical Corporation of the Mitsubishi Chemical Group. "This enzyme could be used as a decomposition accelerator or catalyst for chemical recycling of collected waste plastics." The availability of the purified enzyme also allowed the researchers to examine its structure, with simulations suggesting it was closely related to a different enzyme known to degrade another common polymer: polyethylene terephthalate (PET). "By exploring the enzyme's activity in degrading other polymers, such as PET, we hope that our work will contribute more widely to advances in plastic recycling technologies," Sawabe concludes. This research is part of wider efforts to address the complexity of biodegradable polymer technologies caused by their differing biodegradability on land and in the sea. By learning more about what controls biodegradability in different environments, scientists will hopefully develop polymers that are best suited to the environments they are used in, and those that they may end up in after use.

Elusive fundamental particles called neutrinos are predicted to interact unexpectedly with photons under extreme conditions. Elusive fundamental particles called neutrinos are predicted to interact unexpectedly with photons under extreme conditions. Research at Hokkaido University has revealed that elusive particles called neutrinos can interact with photons, the fundamental particles of light and other electromagnetic radiation, in ways not previously detected. The findings from Kenzo Ishikawa, Professor Emeritus at Hokkaido University, with colleague Yutaka Tobita, lecturer at Hokkaido University of Science, were published in the journal Physics Open. "Our results are important for understanding the quantum mechanical interactions of some of the most fundamental particles of matter," says Ishikawa. "They may also help reveal details of currently poorly understood phenomena in the sun and other stars." Neutrinos are one of the most mysterious fundamental particles of matter. They are extremely difficult to study because they barely interact at all with other particles. They are electrically neutral and have almost no mass. Yet they are highly abundant, with vast numbers constantly streaming from the sun and passing through the Earth, and indeed ourselves, with barely any effect. Learning more about neutrinos is important for testing and perhaps refining our current understanding of particle physics, known as The Standard Model. "Under normal 'classical' conditions, neutrinos will not interact with photons," explains Ishikawa "We have revealed, however, how neutrinos and photons can be induced to interact in the uniform magnetic fields of the extremely large scale -- as large as 103 km -- found in the form of matter known as plasma, which occurs around stars." Plasma is an ionized gas, meaning that all of its atoms have acquired either an excess or a deficiency of electrons, making them negatively or positively charged ions, rather than the neutral atoms that can occur under everyday conditions on Earth. The interaction described by the researchers involves a theoretical phenomenon called the electroweak Hall effect. This is an interaction of electricity and magnetism under extreme conditions where two of the fundamental forces of nature -- the electromagnetic and the weak forces -- merge into the electro-weak force. It is a theoretical concept, expected to apply only in the very high energy conditions of the early universe or within collisions in particle accelerators. The research has derived a mathematical description of this unexpected neutrino-photon interaction, known as the Lagrangian. This describes everything known about the energy states of the system. "In addition to its contribution to our understanding of fundamental physics, our work might also help explain something called the solar corona heating puzzle," says Ishikawa. "This is a long-standing mystery concerning the mechanism by which the outermost atmosphere of the sun -- its corona -- is at a much higher temperature than the sun's surface. Our work shows that the interaction between neutrinos and photons liberates energy that heats up the solar corona." "We now hope to continue our work in search of deeper insights, especially in connection with energy transfer between neutrinos and photons under these extreme conditions," says Ishikawa.