Synthesis ofβ-1,4-Glucan by theβ-Transglucosylase ofSclerotinia libertiana

The β-transglucosylase of Sclerotinia libertiana catalyzed the reaction transferring the non-reducing end glucose of cellotetraitol (G4-OH) to the non-reducing end glucose of G4-OH, and both G3-OH and G5-OH were produced in the reaction at first. A water-insoluble glucan was synthesized by the enzyme, accompanied by the production of soluble cellooligosaccharides such as cellobiose, cellotriose, cellopentaose, and cellohexaose in a prolonged reaction with 2% cellotetraose. The water-insoluble glucan was found to be a linear β-1,4-glucan having an average degree of polymerization of 14 by enzymatic hydrolysis test, methylation, and X-ray analyses. From the results, the β-transglucosylase of Sclerotinia libertiana was defined as a new enzyme able to synthesize higher cellodextrin by a disproportionation reaction of lower molecular weight cellooligosaccharides.