State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, PR China.
Biotechnol Bioeng. 2011 Aug;108(8):1816-27. doi: 10.1002/bit.23122. Epub 2011 Mar 11.
Long-term effects of inoculum pretreatments (heat, acid, loading-shock) on hydrogen production from glucose under different temperatures (37 °C, 55 °C) and initial pH (7 and 5.5) were studied by repeated batch cultivations. Results obtained showed that it was necessary to investigate the long-term effect of inoculum pretreatment on hydrogen production since pretreatments may just temporarily inhibit the hydrogen consuming processes. After long-term cultivation, pretreated inocula did not enhance hydrogen production compared to untreated inocula under mesophilic conditions (initial pH 7 and pH 5.5) and thermophilic conditions (initial pH 7). However, pretreatment could inhibit lactate production and lead to higher hydrogen yield under thermophilic conditions at initial pH 5.5. The results further demonstrated that inoculum pretreatment could not permanently inhibit either methanogenesis or homoacetogenesis, and methanogenesis and homoacetogenesis could only be inhibited by proper control of fermentation pH and temperature. Methanogenic activity could be inhibited at pH lower than 6, both under mesophilic and thermophilic conditions, while homoacetogenic activity could only be inhibited under thermophilic condition at initial pH 5.5. Microbial community analysis showed that pretreatment did not affect the dominant bacteria. The dominant bacteria were Clostridium butyricum related organisms under mesophilic condition (initial pH 7 and 5.5), Thermoanaerobacterium sp. related organisms under thermophilic condition (initial pH 7), and Thermoanaerobacterium thermosaccharolyticum related organisms under thermophilic condition (initial pH 5.5). Results from this study clearly indicated that the long-term effects of inoculum pretreatments on hydrogen production, methanogenesis, homoacetogenesis and dominant bacteria were dependent on fermentation temperature and pH.
长期以来，人们一直研究接种物预处理（加热、酸化、加载冲击）对不同温度（37°C、55°C）和初始 pH 值（7 和 5.5）下葡萄糖产氢的长期影响，采用重复分批培养法进行。结果表明，有必要研究接种物预处理对产氢的长期影响，因为预处理可能只是暂时抑制了氢消耗过程。经过长期培养，与未预处理的接种物相比，预处理接种物在中温条件（初始 pH 值为 7 和 5.5）和高温条件（初始 pH 值为 7）下并没有提高氢气产量。然而，在初始 pH 值为 5.5 的高温条件下，预处理可以抑制乳酸的产生，并导致更高的氢气产率。结果进一步表明，接种物预处理不能永久抑制产甲烷作用或同型产乙酸作用，只有通过适当控制发酵 pH 值和温度才能抑制产甲烷作用和同型产乙酸作用。在中温和高温条件下，当 pH 值低于 6 时，产甲烷作用都会受到抑制，而只有在初始 pH 值为 5.5 的高温条件下，同型产乙酸作用才会受到抑制。微生物群落分析表明，预处理不会影响优势细菌。在中温条件下（初始 pH 值为 7 和 5.5），优势细菌为丁酸梭菌相关菌属；在高温条件下（初始 pH 值为 7），优势细菌为热厌氧杆菌属相关菌属；在高温条件下（初始 pH 值为 5.5），优势细菌为嗜热解糖梭菌相关菌属。本研究结果清楚地表明，接种物预处理对产氢、产甲烷作用、同型产乙酸作用和优势细菌的长期影响取决于发酵温度和 pH 值。
