Published papers

High-molecular weight polyricinoleate having an Mw of 100,600 was enzymatically prepared by the polycondensation of methyl ricinoleate using immobilized lipase from Pseudomonas cepacia (IM-PC) in bulk in the presence of molecular sieves 4A at 80 ºC for 7 days. Polyricinoleate was a viscous liquid at room temperature having a glass transition temperature (Tg) of -74.8 ºC and showed no crystallinity, and biodegraded by activated sludge. Polyricinoleate was readily cured by a dicumyl peroxide at 170 ºC for 30 min to produce a chloroform-insoluble crosslinked polyricinoleate having a hardness of 50º using durometer A.

Aryl C-glycosylation of several glycosyl donors, including unprotected sugars, with phenol and naphthol derivatives in an ionic liquid containing a protic acid proceeded effectively and stereoselectively to give the corresponding aryl C-glycosides in good to high yields. Because the ionic liquid was nonvolatile, the reaction could be carried out under reduced pressure; in addition, the ionic liquid could be reused without loss of effectivelness. The features contribute to the significant advantages of this novel aryl C-glycosylation reaction.

Enzyme-catalyzed synthesis and degradation of a typical diol-diacid type plastic, poly(butylene succinate) (PBS), and diol-diacid type polythioester were studied with respect to the establishment of sustainable polymer production and chemical recycling system. A significantly higher-molecular weight polyester was produced via the ring-opening polymerization of the cyclic oligomer. The cyclic oligomer was produced both by the condensation of monomers and degradation of the polyester. Polymer blends of PBS/poly(L-lactic acid) (PLLA) were degraded into repolymerizable oligomers, first by the lipase-catalyzed degradation of PBS into cyclic BS oligomers followed by the degradation of PLLA into lactic acid oligomers by montmorillonite K-5. By the reprecipitation procedures, the PLLA and BS oligomers were completely separated. Aliphatic dithiol-diacid type polythioesters were enzymatically prepared by the direct polycondensation of dithiol and diacid diesters. A higher molecular weight polythioester was produced using lipase in a two-step procedure, i.e., cyclization with subsequent ring-opening polymerization.

Aliphatic dithiol-diacid type polyethioester were first enzymatically prepared by the direct polycondensation of hexane-1,6-dithiol and diacid diesters using the immobilized lipase from Candida antarctica (lipase CA). Both the melting and crystallization temperatures of the produced polythioesters were higher when compared to those of the corresponding polyoxyesters.

The enzymatic degradation of chemically synthesized typical biodegradable plastics, such as poly(R,S-3-hydroxybutanoate), poly(-caprolactone) and poly(butylene adipate), into reactive cyclic oligomers under the continuous flow of supercritical or subcritical carbon dioxide (scCO2) with toluene through an enzyme column was studied with reference to chemical recycling. It was confirmed that all the tested polymers were quantitatively transformed into the corresponding cyclic oligomers by passage through the column packed with immobilized lipase from Candida antarctica (Novozym 435) at 40 ℃ under the continuous flow of scCO2 with some organic solvent. Compared to the pure organic solvents, by the addition of scCO2 as a mobile phase degradation of the polymer was significantly promoted with respect to the reaction time, temperature and polymer concentration for complete transformation of the polyesters into oligomers through the enzyme column.

The newly designed and synthesized artificial anthracene derivatives possessing a deoxyamino sugar effectively and randomly cleaved proteins, such as bovine serum albumin (BSA) and hen egg lysozyme (Lyso), during photoirradiation using a long wavelength UV light (365 nm) without any further additives. Furthermore, it was found that the cleaving ability of anthracene could be improved by the attachment of a suitable substitute into anthracene core skeleton.