Increasing glutaminase activity in shoyu koji using a mixed culture of two koji moulds

Abstract

For improved fermentation of shoyu (soy sauce), a useful koji-making system has been developed using a mixed tane-koji of two shoyu koji moulds, namely Aspergillus oryzae K2 (length of conidiophores about 350 μm) and the late-conidiation strain, A. oryzae HG (length of conidiophores about 2500 μm). The mixed culture of strains K2 and HG had about twice the glutaminase activity of the single-strain cultures. In addition, the number of conidia in the mixed culture was about 10% of that in a culture of strain K2 alone.