title: Formation of ethyl ferulate by rice koji enzyme in sake and mirin mash conditions.
abstract: Formation mechanism of ethyl ferulate (EF) in sake and mirin mash conditions was investigated to understand EF level control in the manufacturing process. Rice koji formed EF from ferulic acid (FA) and ethanol and decomposed EF to FA. This did not occur in sake yeast and chemical esterification was rare. Esterification of FA and hydrolysis of EF by rice koji might be due to feruloyl esterase(s). The rice koji enzyme showed normal Michaelis-Menten kinetics for FA in ethyl esterification and for EF in hydrolysis, but not for ethanol in the esterification reaction. Substrate specificity of the rice koji enzyme for hydroxycinnamic acids suggested that the main enzyme involved might be similar to type A feruloyl esterase. We studied the rice koji enzyme properties, short-term digestion of steamed rice grains with exogenous ethanol and small scale mirin making with pH adjustment. Our results suggested differences in the esterification and hydrolysis properties of the enzyme, in particular, different pH dependencies and different behaviors under high ethanol conditions; these factors might cause the differing EF levels in sake and mirin mashes.
authors.affiliation: Department of Biological Resource Sciences, Akita Prefectural University, Nakano Shimoshinjyo, Akita 010-0195, Japan. hashizume@akita-pu.ac.jp
authors.forename: Katsumi
authors.initials: K
authors.lastname: Hashizume
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ito
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishizuka
authors.forename: Naoki
authors.initials: N
authors.lastname: Takeda
mesh_terms: D000434:Alcoholic Beverages; D002109:Caffeic Acids / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D003373:Coumaric Acids / Q000378:metabolism; D004951:Esterification; D000431:Ethanol / Q000378:metabolism; D012275:Oryza / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013227:Steam
chemical_list: D002109:Caffeic Acids; D003373:Coumaric Acids; D013227:Steam; D000431:Ethanol; C099085:ethyl ferulate; C004999:ferulic acid; D002265:Carboxylic Ester Hydrolases; C070196:feruloyl esterase