A two-stage procedure was developed for the preparation of the soy yeast starter Zygosaccharomyces rouxii, which is added to the mash (moromi) in the fermentation process for the production of soy sauce (shoyu). In the first stage, the yeast was cultured in a medium containing 9% (w/v) NaCl at 30 degrees C. In the second stage, the starter culture was supplemented with 16% (w/v) NaCl at 15 degrees C in order to maintain high growth and fermentation activities of the yeast cells as well as to minimize microbial contamination.