Water Activity Dependence of Lipases in Non-aqueous Biocatalysis

Abstract

Eleven lipases are tested and it was found that lipases can be divided into three types according to water activity dependence. The first type is lipase that has low water activity dependence and works in a low water activity, its performance changes little with the change of water activity. The optimum water activity is 0.19 and Newlase F (Rhizopus niveus), lipase FAP-15 (Rhizopus oryzae) belong to this type. The second type is lipase that has medium water activity dependence and its performance changes with the change of water activity. Most lipases belong to this type and the optimum water activity in this type is about 0.60. The third type is lipase that has a high water activity dependence and works only in a high water activity (a ( w ) > 0.75). WGL (wheat germ) belongs to this type and the optimum water activity is 0.90. The relationship between enantioselectivity and water activity is also discussed and the enantioselectivity seems to be independent of water activity. And we also compared the two control methods of water activity, it was found that the method which add solid salt hydrates to the reaction mixture (method II) is more stable and effective throughout the reaction than the method that pre-equilibrate via the vapor phase (method I). The addition concentration of salt hydrates is also investigated and the optimum concentration is 1 g/l.

Improving activity and enantioselectivity of lipase via immobilization on macroporous resin for resolution of racemic 1- phenylethanol in non-aqueous medium

“…It indicates that high water content may lead to an increase in hydrolysis, resulting in the decrease in transesterification activity of the enzyme. For the immobilized lipase, the enzyme activity and ee s also showed a similar decrease in tendency, which can be explained as that extra water would accumulate inside the immobilized lipase and influence the flexibility of the protein [ 21 ]. Therefore, there is no necessity to add extra water during the reaction, as the immobilized lipase has contained necessary water to maintain its active conformation during immobilization process.…”

Lipase‐catalyzed interesterification reactions for human milk fat substitutes production: A review

“…Under these circumstances, it is essential to control the a w of the catalyst as it will directly determine the performance of the synthesis, namely its yield, selectivity, and stability 26. As a result, carrying out transfer reactions catalyzed by lipases requires a preliminary study of the influence of the a w of the enzyme on kinetics and reaction yield 27–32. By studying water activity, one can define the optimum conditions of hydration necessary for maximum enzyme activity in acyl transfer catalysis and limit competitive hydrolysis reaction.…”

“…By studying water activity, one can define the optimum conditions of hydration necessary for maximum enzyme activity in acyl transfer catalysis and limit competitive hydrolysis reaction. Sorption isotherms of the enzyme, representing its water content plotted against water activity ( a w ) at constant temperature can then be studied to determine the moisture content corresponding to the optimum a w of the biocatalyst 28–33. The optimum a w for most lipase preparations is generally between 0.25 and 0.45, which usually corresponds to moisture contents between 0.5 and 1% 34.…”

Activity of immobilized Thermomyces lanuginosus and Candida antarctica B Lipases in Interesterification Reactions: Effect of the Aqueous Microenvironment

“…In these circumstances, it is essential to control the a w of the catalyst as it will directly determine the performance of the synthesis, namely its yield, selectivity and stability [7]. Therefore, the carrying out of acyl transfer reactions biocatalyzed by lipases requires a preliminary study of the influence of the a w of the enzyme on kinetics and reaction yield [8][9][10][11][12][13]. By studying the water activity, one can define the optimum conditions of hydration combining maximum enzyme activity for the acyl transfer catalysis and limiting the competitive hydrolysis reaction.…”