Abstract: The effects of weight-average molecular mass (Mw) of konjac glucomannan (KGM) and acyl donors on its acylation catalyzed by an immobilized lipase Novozym 435 in t-BuOH were investigated. The results demonstrated that the Mw of KGM had a significant effect on the acylation. The initial reaction rate and degree of substitution of the product decreased with the increase in Mw of KGM. These could be related to the difference in solubility of KGM, viscosity of the reaction system, steric hindrance, and granule structure of KGM with different Mw values. When fatty acid vinyl esters were used as acyl donors for the Novozym 435-catalyzed acylation of KGM in t-BuOH, the initial reaction rate and substitution degree of the product decreased with increasing carbon-chain length of fatty acid vinyl esters. Novozym 435-catalyzed acylation of KGM with various acyl donors in t-BuOH was highly regioselective and occurred predominantly at the C6-OH group of KGM.

Key words: konjac glucomannan, acylation, regioselectivity, lipase, weight-average molecular mass, acyl donor