Cheng S S, Chang S M, Chen S T
Department of Environmental Engineering, National Cheng-Kung University, Tainan, Taiwan.
Water Sci Technol. 2002;46(4-5):209-14.
Hydrogen fermentation using glucose as a single substrate caused abrupt pH drops and the gradual losses of hydrogen producers, which in turn led to system failure. In this study the use of a proteinaceous substrate, peptone, avoided the abrupt pH drops in the reactive system and allowed for further exploration of volatile fatty acids (VFAs) and pH effects on the hydrogen fermentation process. Our results showed that: (1) during the hydrogen fermentation tests, the abrupt pH drops were avoided thus system stability increased due to the production of ammonia from the peptone fermented, (2) pH control was not necessary and the addition of acetate to the process had little effect on the hydrogen fermentation process, (3) at the extreme pHs the addition of acetate either lengthened the lag phase (pH < or = 6) or slowed the hydrogen production rate (pH > or = 8), and both situations were not desired, and (4) high VFA content in the system sped up the consumption of hydrogen gas. Results of this study suggested that the hydrogen fermentation using the protein-containing substances as substrate was beneficial in maintaining the system pH. As long as the pH was maintained around 6-8, system inhibition due to VFAs accumulation was minimized. Thus, the optimal operation of a hydrogen fermentation process would be achievable via the control of substrate composition at a certain carbohydrate-to-protein ratio.
以葡萄糖作为单一底物进行氢气发酵会导致pH值急剧下降以及氢气产生菌逐渐损失，进而导致系统失效。在本研究中，使用蛋白质类底物蛋白胨避免了反应系统中pH值的急剧下降，并允许进一步探索挥发性脂肪酸（VFAs）和pH值对氢气发酵过程的影响。我们的结果表明：（1）在氢气发酵试验期间，由于蛋白胨发酵产生氨，避免了pH值的急剧下降，从而提高了系统稳定性；（2）不需要进行pH控制，向该过程中添加乙酸盐对氢气发酵过程影响不大；（3）在极端pH值下，添加乙酸盐要么延长了延滞期（pH≤6），要么降低了氢气产生速率（pH≥8），这两种情况都不理想；（4）系统中高含量的VFAs加速了氢气的消耗。本研究结果表明，以含蛋白质物质作为底物进行氢气发酵有利于维持系统pH值。只要将pH值维持在6 - 8左右，由于VFAs积累导致的系统抑制就会降至最低。因此，通过控制底物组成使其具有一定的碳水化合物与蛋白质比例，就可以实现氢气发酵过程的最佳运行。
