Treatment of, and Candida utilis biomass production from shochu wastewater; the effects of maintaining a low pH on DOC removal and feeding cultivation on biomass production.

Shochu wastewater (SW; alcoholic distillery wastewater) contains large amounts of organic compounds (25,000 - 60,000 COD mg/L), nitrogen (1,000 - 6,000 T-N mg/L), and phosphorus (500 - 1,000 T-P mg/L). Despite its high nutrient content, SW is highly perishable, which limits its utilization for animal feed and fertilizer. Therefore, SW is mainly treated by methane fermentation. On the other hand, a feed yeast, Candida utilis, can utilize various organic compounds and be utilized as a yeast extract source and animal feed. We previously bred a mutant, C. utilis UNA1, that accumulates a large amount of nitrogen. Here, we investigated the use of C. utilis UNA1 to treat highly concentrated SW. With fed-batch cultivation using a 5-L jar fermenter, controlling pH at 5.0 with H2SO4, 62.9% of DOC, 38.4% of DTN, and 44.5% of DTP were stably removed from non-diluted barley shochu wastewater (BSW), and about 16.7 kg of freeze-dried yeast biomass was obtained. The yeast sludge biomass generated from BSW contains about 60% crude protein. Furthermore, using H2SO4 to control pH increased the sulfur content of wastewater, which increased the methionine composition of yeast sludge biomass.