为研究不同液化pH对玉米酒精同步糖化发酵的影响,以我国目前玉米酒精生产工艺为基础构建玉米酒精发酵模型,研究不同液化pH对液化、发酵过程和发酵成熟醪指标的影响。结果表明,液化还原糖在液化pH为5.6时最高,分别较液化pH为5.2和4.8的提高16.48%和121.08%;在液化pH为4.8~5.6内的CO2失重标准差表明,该模型稳定性良好,最大标准差仅为0.55,同时发酵CO2的失重速率随着液化pH的提高而下降;发酵成熟醪酒精浓度在液化pH 5.6的最高,分别较液化pH 5.2和4.8提高0.32%和1.18%;发酵成熟醪残淀粉浓度在液化pH 5.6的分别较液化pH 5.2和4.8的降低0.66%和5.26%;同时发酵成熟醪残过滤总糖浓度在液化pH 5.6的分别较液化pH 5.2和4.8的降低3.61%和提高11.93%。因此,玉米酒精生产过程必需同时兼顾耐高温α-淀粉酶的作用效果和发酵初期的还原糖浓度,以保证发酵速率和发酵成熟醪指标。
In order to investigate the influence of different liquefied mash pH on corn ethanol production, a simultaneous saccharification and fermentation process model based on the current industrial corn ethanol production process was established. Based on the stability of this process model, the properties of liquefied mash, the performance of CO2 mass loss during ethanol fermentation and the main indexes of mature fermented mash were measured. Results showed that compared with liquefied mash pH 5.2 and 4.8, the reducing sugar content obtained in liquefied mash of pH 5.6 increased by 16.48%(P<0.01) and 121.08% (P<0.01), respectively. The process model on CO2 mass loss was stable, with the highest standard deviation only at 0.55 (pH=5.2, 48 h). At the same time, with the increase of pH of liquefied mash from pH 4.8 to 5.6, the CO2 mass loss speed became low. Compared with liquefied mash pH 5.2 and 4.8, the ethanol content obtained in mature fermented mash at pH 5.6 increased by 0.32% (P>0.05) and 1.18% (P<0.05), respectively. Meantime, the residual starch content obtained in mature fermented mash at pH 5.6 was higher by 0.66% (P>0.05) and 5.26% (P<0.05), respectively. Additionally, the total residual filtered sugar content in mature fermented mash at pH 5.6 was significantly lower by 3.61% (P<0.01) and extremely significantly higher by 11.93% (P<0.01). This study indicated that it should be necessary to adjust reasonable liquefied mash pH on the α-amylase as well as reducing sugar content in the liquefied mash on the initial ethanol fermentation.
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