2. By the early 1970s it had change into a standard follow to add pure tradition strains of yeasts ( Saccharomyces rouxii and sometimes Torulopsis spp .) and amino acids suppliers bacteria to the moromi mash to accelerate the fermentation and enhance the shoyu high quality. In 1975 main manufacturers started to omit chemical preservatives and add a small amount (0.5-1%) of alcohol (ethanol; the same as found in wine or beer) to boost the total alcohol content over 2.5%.