Development of a novel biotechnology for decomposing of plastic using PET (polyethylene terephthalate)-decomposing microorganisms

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The results in this research are as follows.1.Screening, isolation, and identification of PET-decomposing microorganisms : We have succeeded in getting six strains, which could decompose the non-crystalline PET fibers. Some of them were identified as Trichosporon sp.No.85, Sphingomonas paucimobilis No.77-2, and Arthrobacter sp.No.97-2, respectively.2.Purification of PET-decomposing enzyme from Arthrobacter sp.No, 97-2 : A 35-kDa protein was purified as a candidate for PET-decomposing enzymes from the culture filtrate of Arthrobacter sp.No.97-2. The amino-terminal sequence of the purified enzyme showed high similarity with that of flagellin (identity ; 63% and similarity ; 75%). We could not elucidate enzymatic properties, because of low specific activity.3.Development of new assay methods : Observations of the surface of PET fiber by a scanning electron microscopy and measurements of tensile strength of PET fiber have been used for assay of PET-decomposing activities. However, these assay methods take a lot of time, and also their data are not accurate. To improve assay methods for PET-decomposing enzymes, measurements of viscosity, gel permeation chromatography, and NMR spectroscopy were introduced. Four kinds of substrates were used : PET fiber, PET film, PET oligomer, and OEST (oligo (ethylene succinate-co-terephthalate). These assay methods turned out to be useful for assay of PET-decomposing activities.Some of our researches were not carried. The reasons are (1) it was very difficult to keep such PET-decomposing strains with high activities. These enzymes might be coded on plasmids. (2) There were no any adequate assay methods, which are reliable.