초록
Ethanol production by Saccharomyces cerevisiae NP 01 from sweet sorghum juice was conducted under nutrient supplementation and/or aeration conditions. Yeast extract (YE) and dried spent yeast (DSY) were used as nitrogen supplements. Under high gravity (HG, ~200gl<SUP>-1</SUP> of total sugar) conditions, the addition of either 6gl<SUP>-1</SUP> of YE or 9gl<SUP>-1</SUP> of DSY did not increase the ethanol concentration (P), but it promoted the rate of ethanol production or ethanol productivity (Q<SUB>p</SUB>). The Q<SUB>p</SUB> value of the control treatment (no supplement) was 1.96gl<SUP>-1</SUP>h<SUP>-1</SUP>. The P (93.4-94.0gl<SUP>-1</SUP>) and Q<SUB>p</SUB> (3.89-3.92gl<SUP>-1</SUP>h<SUP>-1</SUP>) values under the YE and DSY supplementation were comparable, indicating that DSY could be used to replace YE in ethanol production. Under very high gravity (VHG, ~280gl<SUP>-1</SUP> of total sugar) conditions, the supplementation of nitrogen and trace elements (Zn<SUP>2+</SUP>, Mg<SUP>2+</SUP> and Mn<SUP>2+</SUP>) coupled with the aeration supply were required to improve the ethanol production efficiency. Under the supplementation (in gl<SUP>-1</SUP>) of DSY (13.5), Zn<SUP>2+</SUP> (0.01), Mg<SUP>2+</SUP> (0.05) and Mn<SUP>2+</SUP> (0.04) in the presence of aeration supply at 0.05vvm for 12h, the P and Q<SUB>p</SUB> values were 126.3gl<SUP>-1</SUP> and 2.11gl<SUP>-1</SUP>h<SUP>-1</SUP>, respectively. The P and Q<SUB>p</SUB> values under the same supplementation without aeration were 114.8gl<SUP>-1</SUP> and 1.91gl<SUP>-1</SUP>h<SUP>-1</SUP>, respectively, and these values under no supplementation and no aeration were 108.0gl<SUP>-1</SUP> and 1.50gl<SUP>-1</SUP>h<SUP>-1</SUP>, respectively. In addition, glycerol (the main by-product during ethanol fermentation) under aeration conditions was ~3gl<SUP>-1</SUP> lower than that without aeration.