リパーゼの応用 (第2報)

2種リパーゼ剤による米ぬかろうの分解

抄録

In the previous study, we found natural wax esters to be hydrolyzed by the particular commercial lipase preparations when an organic solvent was present in the reaction mixture. In all cases of vegetable wax esters, lipase activity required to bring about the same degree of hydrolysis differed signicficantly according to the enzyme source.
The present study was carried out to clarify the above phenomenon, using a rice bran wax with two lipases from Candida cylindracea (Can.) and Rhizopus chinensis (Rh.). To obtain reaction products for the same degree (11%) of hydrolysis of a rice bran wax in each case, Can. lipase was required in an amount that would provide 5000 U of lipase activity, while for Rh. lipase, the amount that would give 150 U under the same reaction conditions. An assay of the above reaction products indicated Rh. lipase liberate the saturated longer-chain fatty acids constituting the rice bran wax more than Can. lipase, although no significant difference was observed in alcohol specificity under the reaction conditions tested. Also Can. lipase was inactivated much faster in the reaction mixture with the organic solvent than Rh. lipase which had previously been identified as fairly thermostable. Thus, differences in the degree of hydrolysis of the wax ester caused by both enzymes may primarily arise from those in stability and substrate specificity of the two enzymes.
It is thus concluded that at least three properties of an enzyme, thermostability, stability in the reaction mixture with an organic solvent, and reactivity on long chain monoesters, are critical indexes for the screening of an appropriate enzyme or microorganism producing an enzyme which applicable to the industrial hydrolysis of natural wax esters.