Kyoto Institute of Technology, Japan
Nariyoshi Kawabata completed his PhD degree from Kyoto University at 1963. He was a chemistry assistant at Kyoto University from 1963 to 1969. He was an assistant professor of Kyoto Institute of Technology from 1969 to 1976 and a professor from 1976 to 1999. He was a professor of University of Shiga Prefecture from 1999 to 2005. He has a faithful opinion about severe duty of chemists in the protection of natural abundant environment from harmful and obstructive chemical materials produced by chemists and chemical industry.
My research group accidentally discovered powerful capture of bacterial cells in the living state on the surface of cross-linked poly(N-benzyl-4-vinylpyridinium bromide), PBVP(Br), during development of a new technology for water purification without leaving chemical materials in the treated water. During this research, we encountered with violent proliferation of bacteria on the polymer surface which was covered with proliferated bacteria that resembled a group of breeding mold although there was no organic material other than the polymer and bacteria. After about ten years, we were shocked by violent digestion of cross-linked PBVP(Br) by activated sludge when placed in a continuous aerobic treatment of artificial sewage by activated sludge. We tried to prepare biodegradable vinyl polymers by connection of oligomers of vinyl compounds by BVP, since oligomers of vinyl compounds are biodegradable different from vinyl polymers. Half-life of polystyrene that contained 10.6 mol % of BVP (the oligomer portion was about octamer) was only 13 days when treated with activated sludge in soil in spite of the fact that no degradation of oligomers larger than trimer of styrene by bacterial strain was reported. We realized that BVP is not only a highly biodegradable chemical unit useful to connect oligomers, but also strongly stimulates microbes to degrade the oligomer portion connected to BVP. I keenly realized the great importance of the grant of highly nutritive worth for microbes in charge of biodegradation in the preparation of biodegradable synthetic polymers.