Abstract
A model system was employed to investigate the role of glutaminase in soy sauce fermentation. In this system, a soybean protein was used as the starting material and a water extract of wheat bran koji was used as the enzyme preparation containing proteinases, peptidases, glutaminases and so on. A soybean protein was digested with the enzyme preparation. γ-Glutamylserine, γ-glutamylglutamic acid and γ-glutamylalanine were isolated from an acidic fraction of the soybean protein digest.
The addition of the purified glutaminase from Aspergillus oryzae led to more production of glutamic acid and γ-glutamyl peptide and less production of glutamine and pyroglutamic acid, γ-Glultamyltranspeptidase activity and γ-glutamyl peptide(s) were also detected in a practical soy sauce mash.
