Glucosyltransferase (GTase) is a kind of important enzyme which can convert α-1,4 glycosidic bond into other glycosidic bond.The modified product can be used as a new type of dietary fiber.The glucosyltransferase gene from Lactobacillus reuteri was heterologously expressed.The purified GTase was analyzed for its enzymatic properties and function.The results showed that the molecular weight of GTase is 105 kDa,the enzyme was stable at pH 7.0-8.5,the residual enzyme activity remained above 80% after being stored at 4 ℃ for 12 h.The optimum temperature and pH were 40 ℃ and 5.0 respectively.Under these conditions,Ca2+ could increase the enzyme activity by about 2.1-fold.The Km and Vmax of GTase to maltodextrin (DE12) were (1.18±0.21) g/L and 2.6×10-6 g/s respectively.When maltodextrin (DE12) was reacted with GTase at 40 ℃ for 72 h,the content of α-1,6 glycosidic bond was increased by 38.4%,the content of rapidly digestible starch was decreased by 25.96%,the content of slowly digestible starch and resistant starch were increased by 8.97% and 17.76% respectively.
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