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以嗜热丁酸梭菌为生产菌株,研究不同pH(6.0,6.2,6.4,6.6,6.8,7.0)条件对嗜热丁酸梭菌生长和产酸的影响。基于不同pH条件下试验结果的分析比较,拟采用pH-shift控制策略,运用发酵法制备丁酸,并探索最优工艺条件。通过单因素试验和正交优化试验确定了最优发酵工艺条件为:0~20 h将pH控制在6.8,而后将pH调低至6.2并保持到发酵结束,发酵温度为55℃,发酵总时间为50 h,以6 mol/L NaOH溶液为中和剂,采用自动流加方式。优化后的发酵工艺能有效提高丁酸产量,通过应用pH-shift控制策略,丁酸产量达16.12 g/L,与固定pH条件下发酵最好结果相比提高35.69%。该试验结果表明采用pH-shift控制策略的新工艺可有效提高丁酸发酵过程的效率。
Clostridium thermophilium was used as production strain to study the effects of different pH (6.0, 6.2, 6.4, 6.6, 6.8, 7.0) conditions on Clostridium thermophilus growth and acid production. Based on the comparison and analysis of the test results under different pH conditions, the pH-shift control strategy is proposed to use the fermentation method to prepare butyric acid and to explore the optimum process conditions. Through single factor test and orthogonal test, the optimal fermentation conditions were as follows: the pH was controlled at 6.8 after 0 ~ 20 h, then the pH was reduced to 6.2 and maintained at the end of fermentation, the fermentation temperature was 55 ℃, the total fermentation time 50 h, with 6 mol / L NaOH solution as neutralizer, using automatic flow mode. The optimized fermentation process can effectively increase the yield of butyric acid. By using pH-shift control strategy, the yield of butyric acid is 16.12 g / L, which is 35.69% higher than the best fermentation under the condition of constant pH. The results show that the new technology with pH-shift control strategy can effectively improve the efficiency of butyric acid fermentation process.