以我国目前玉米酒精生产工艺为基础,通过选择液化[拌料干物浓度(dry solid, DS)、液化pH、液化时间、耐高温α-淀粉酶剂量、液化温度]和同步糖化发酵(葡萄糖淀粉酶剂量、酵母接种量、发酵温度等)等过程主要控制参数建立实验室玉米酒精发酵方法。实验确定液化条件为拌料DS 25%、液化pH 5.6、液化时间120 min、耐高温α-淀粉酶剂量40 U/g、液化温度88 ℃,此时液化醪黏度(91.2±2.8) mPa·s、还原糖为(11.65±0.03) g/100 g,符合同步发酵玉米酒精的液化指标要求。实验确定同步糖化发酵条件为葡萄糖淀粉酶剂量150 U/g、酵母接种量3%、发酵温度32 ℃,在该条件下酒精发酵过程稳定,CO2失重数据最大标准差为0.38,占相应CO2平均失重仅为2.96%;在发酵成熟醪中乙醇含量为(12.58±0.04) g/100 mL,发酵效率为97.71%,粮酒转化率为2.425 t/t,实验结果符合我国玉米酒精生产的实际情况。因此该方法可以为酒精生产工艺的优化及原辅料的选择提供数据参考。
Based on the current industrial corn ethanol production process in China, the laboratory corn ethanol fermentation method was established by optimizing the main liquefaction process indexes (mixing DS (Dry Solid, dry matter concentration), liquefaction pH, liquefaction time, thermostable α-amylase dose, liquefaction temperature) and main SSF (simultaneous saccharification and fermentation process) process indexes (glucoamylase dose, yeast inoculum and fermentation temperature).Under the conditions of mixing DS 25%, liquefaction pH 5.6, liquefaction time 120 min, liquefaction temperature 88 ℃ and thermostable α-amylase dose 40 U/g, the reducing sugar content in liquefied mash was (11.65±0.03) g/100 g and the viscosity of liquefied mash was (91.2±2.8) mPa.s, which was consistent with actual industrial corn ethanol SSF production process.The SSF conditions were determined as follows:glucoamylase dosage 150 U/g, yeast inoculation amount 3%, fermentation temperature 32 ℃.Under these conditions, the alcohol fermentation process was stable, and the maximum standard deviation of CO2 mass loss was 0.38, accounting for only 2.96% of the corresponding CO2 average mass loss.In the fermented mature mash, the ethanol content was (12.58±0.04) g/100 mL, the fermentation efficiency was 97.71%, and the conversion rate of corn flour to ethanol was 2.425 t/t, which was consistent with the normal range of actual corn ethanol production of Chinese.Based on the actual production process, this method can provide data reference for the optimization of alcohol production process and the selection of raw materials.
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