初始pH值对产氢产乙酸/耗氢产乙酸两段耦合工艺定向生产乙酸的影响

以葡萄糖为底物,以经加热预处理并活化过的厌氧污泥为种泥,研究了初始pH值对产氢产乙酸/耗氢产乙酸两段耦合工艺厌氧发酵定向生产乙酸的影响。实验考察了7个初始pH值(5、6、7、8、9、10、11)条件下的底物降解、产物产生和发酵过程pH值的变化。结果表明:产氢产乙酸段初始pH值的变化不仅影响本阶段产酸,而且影响耗氢产乙酸段产酸。初始pH=5时主要进行乙醇型发酵;pH=6和7时主要进行丁酸型发酵;pH=8时混合酸型发酵类型逐渐占优势,pH=8~11时均以乙酸为主要产物,耦合系统生产乙酸最优初始pH值为10。在初始pH=8~11范围内,产氢产乙酸段初期的乙醇浓度一般较高,但到后期因乙醇被微生物进一步代谢转化成乙酸而使其含量下降。

Acetate Production by Acidification-homoacetogenesis Two-phase Coupling Process: Effect of Initial pH

The effect of initial pH values on acetate production was studied in the acidification-homoacetogenesis two-phase coupling system using glucose as the substrate and the heat-treated and activated anaerobic sludge as the inoculum. Substrate degradation, product yield and pH variation during fermentation were examined at various initial pH values (5, 6, 7, 8, 9, 10 and 11). The results show that initial pH values affect volatile fatty acids and ethanol production not only in the acidification phase itself but also in the homoacetogenesis phase. Ethanol-type fermentation mainly takes place at initial pH 5 while butyrate-type fermentation at initial pH 6 and 7. But acetate is the dominant product at initial pH 8-11. The optimal initial pH value is 10 for acetate production in the two-phase coupling system. At initial pH 8-11, ethanol concentration is highest at the beginning of acidification, but there is a subsequent decline as ethanol is converted to acetate as a result of further metabolism of the microbes.