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

Takashi Watanabe,Haruyuki Iefuji,Hiroko K Kitamoto

doi:10.1186/2193-1801-2-514

Abstract

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.

Highlights

Shochu is a traditional Japanese distilled liquor made from barley, sweet-potato, rice, and other crops
The amounts of Dissolved organic carbon (DOC), Dissolved total nitrogen (DTN), and DTP removed by C. utilis UNA1 were higher than those removed by C. utilis IFO1086 (Table 2)
These results were similar to previous results using barley shochu wastewater (BSW) (Table 2, (Watanabe et al 2013a)), indicating that organic compounds of shochu wastewater (SSW) are good substrates for C. utilis biomass production

Summary

Introduction

Shochu is a traditional Japanese distilled liquor made from barley, sweet-potato, rice, and other crops. Shochu waste has high concentrations of suspended solids (30,000 – 65,000 SS mg/L), 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) This makes it too expensive to treat by the conventional activated sludge method. The main treatment method of shochu waste is solid–liquid separation, Previously, the National Research Institute of Brewing (NRIB) of Japan developed an aerobic wastewater treatment method using a combination of yeasts and activated sludge (Yoshizawa 1978). This system removes large amounts of organic compounds, requires little space, and discharges little waste sludge. This method is useful for treating food and beverage industry wastewater (Yoshizawa 1978) and has been used to treat SW in laboratory experiments for over thirty years (Saito et al 1983; Suzuki et al 1991; Watanabe et al 2009; Yoshii et al 2001)

Methods

Results

Conclusion