Industrial wastes from pulp and food plants were treated with microorganisms to clarify organic waste-water and to produce cells as animal feed, and results were summarized as follows.
(1) Waste-water from pulp, beer, bread yeast, and ethanol distillation plants contained 1.4∼1.5% of total sugar, 0.25∼0.35% nitrogen, and biological oxygen demand (BOD) was 400∼25,000, chemical oxygen demand (COD), 500∼28,000, and pH, 3.8∼7.0. The BOD and COD were highest in waste-water from ethanol distillation plants among others. (2) Bacterial and yeast counts were 4×10⁴-1×10^9, 2×10²-7×10⁴/㎖ in waste-water. (3) Bacteria grew better in pulp waste and yeasts in beer, bread yeast, and ethanol distillation waste. (4) Saccharomyces cerevisiae SAFM 1008 and Candida curvala SAFM 70 were the most suitable microorganisms for clarification of ethanol distillation waste. (5) When liquid and solid waste from ethanol distillation were treated with microbial cellulose, xylanase, and pectinase, solid waste was reduced by 36%, soluble waste was increased, and recuding sugar content was increased by 1.3 times which provided better medium than untreated waste for cultivation of yeasts. (6) Optimum growth conditions of the two species of yeast in ethanol distillation waste were pH 5.0, 30℃, and addition of 0.2% of urea, 0.1% of KH₂PO₄ and 0.02% of MgSO₄. (7) Minimum number of yeast for proper propagation was 1.8×10^5/㎖. (8) C. curvata 70 was better than cerevisae for the production of yeast cells from ethanol distillation waste treated with microbial enzymes. (9) S. cerevisiae produced 16 g of dried cell per 1,000㎖ of ethanol distillation waste and reduced BOD by 46% C. casrvata produced 17.6 g of dried cell and reduced BOD by 52% at the same condition. (10) Yeast cells produced from the ethanol distillation waste contained 46-52% protein indicating suitability as a protein source for animal feed.
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