Graves Tara, Narendranath Neelakantam V, Dawson Karl, Power Ronan
Alltech Biotechnology Center, 3031 Catnip Hill Pike, Nicholasville, KY 40356, USA.
Appl Microbiol Biotechnol. 2007 Jan;73(5):1190-6. doi: 10.1007/s00253-006-0573-5. Epub 2006 Oct 21.
The combined effects of lactic acid and acetic acid on ethanol production by S. cerevisiae in corn mash, as influenced by temperature, were examined. Duplicate full factorial experiments (three lactic acid concentrations x three acetic acid concentrations) were performed to evaluate the interaction between lactic and acetic acids on the ethanol production of yeast at each of the three temperatures, 30, 34, and 37 degrees C. Corn mash at 30% dry solids adjusted to pH 4 after lactic and acetic acid addition was used as the substrate. Ethanol production rates and final ethanol concentrations decreased (P<0.001) progressively as the concentration of combined lactic and acetic acids in the corn mash increased and the temperature was raised from 30 to 37 degrees C. At 30 degrees C, essentially no ethanol was produced after 96 h when 0.5% w/v acetic acid was present in the mash (with 0.5, 2, and 4% w/v lactic acid). At 34 and 37 degrees C, the final concentrations of ethanol produced by the yeast were noticeably reduced by the presence of 0.3% w/v acetic acid and >or=2% w/v lactic acid. It can be concluded that, as in previous studies with defined media, lactic acid and acetic acid act synergistically to reduce ethanol production by yeast in corn mash. In addition, the inhibitory effects of combined lactic and acetic acid in corn mash were more apparent at elevated temperatures.
研究了乳酸和乙酸对玉米醪中酿酒酵母乙醇生产的联合影响，以及温度对其的影响。进行了重复的全因子实验（三种乳酸浓度×三种乙酸浓度），以评估在30℃、34℃和37℃这三个温度下，乳酸和乙酸对酵母乙醇生产的相互作用。添加乳酸和乙酸后，将干物质含量为30%的玉米醪调节至pH 4，用作底物。随着玉米醪中乳酸和乙酸的总浓度增加，以及温度从30℃升高到37℃，乙醇生产率和最终乙醇浓度逐渐降低（P<0.001）。在30℃时，当醪中存在0.5% w/v乙酸（同时含有0.5%、2%和4% w/v乳酸）时，96小时后基本不产生乙醇。在34℃和37℃时，0.3% w/v乙酸和≥2% w/v乳酸的存在显著降低了酵母产生的乙醇最终浓度。可以得出结论，与之前在特定培养基中的研究一样，乳酸和乙酸协同作用，降低了玉米醪中酵母的乙醇产量。此外，在高温下，玉米醪中乳酸和乙酸的联合抑制作用更为明显。
