Breeding of the Zygosaccharomyces rouxii DBH114 strain for miso products to prevent re-fermentation after packaging

Abstract

Ethanol is added to prevent re-fermentation of yeast in miso that is not heat-sterilized, but this increases manufacturing costs. In response to a request from the Hiroshima Prefecture Miso Cooperative to reduce the amount of ethanol used, we developed the yeast DBH114 strain for miso manufacturing. Mutant strains were obtained from the 　D-9 strain used in the Cooperative. The DBH114 strain was selected by assessing its ethanol sensitivity and ethanol production ability in liquid cultures. In a small-scale miso manufacturing test (total weight of 2 kg), it was confirmed that the DBH114 strain produced an amount of ethanol equivalent to that of the D-9 strain and met the target of easy breakdown. In miso manufacturing with a total weight of 1,000 kg, the DBH114 strain suppressed re-fermentation at a lower ethanol concentration than the D-9 strain, indicating the possibility of reducing the amount of ethanol added.