It has been found, in this study, that a new ethanol-type fermentation can be obtained in a continuous flow, high-rate acidogenic reactor receiving molasses as the feed. The operating pH must be maintained at about 4.5 to avoid onset of propionic fermentation. The acidogenic reactor had a VSS level of 20g/L and its organic loading was as high as 80 to 90kg COD/m3d. The operating ORP was around −250mV. The ethanol-type fermentation was characterized by a simultaneous production of acetic acid and ethanol, while the yield of propionic was minimal even at a high organic loading rate of 80 to 90kg COD/m3d, and also, the hydrogen partial pressure was as high as 50kPa. Thus, this study has shown that the production of propionic acid is not always related to high hydrogen partial pressure. When the operating pH was increased to 5.5, the yield of propionic acid became significant.

应用双梯度-变性梯度凝胶电泳（DG2DGGE）对生物制氢反应器微生物种群的动态变化及多样性进行监测。间隔7d从反应器取厌氧活性污泥，以细菌16SrDNA通用引物进行V2～V3区域PCR扩增，长约450bp的PCR产物经DGGE分离后，获得污泥微生物群落的16S rDNA指纹图谱。污泥接种到反应器后微生物群落中既有原始种群的消亡和增长，也有次级种群的强化和演变。反应器在运行初期群落演替迅速，15d时微生物群落结构变化最大。群落结构的相似性随着演替时间的增加而逐渐升高，种群动态变化后形成稳定的群落结构。29d时微生物多样性基本保持不变，微生物优势种属达到19个OTU。在细菌竞争和协同作用制约下，种群多样性降低后趋于稳定，形成顶级群落。有些种群在群落结构中一直存在，是群落建成的原始种群，原始种群与次级种群在代谢过程中具有协同作用，表现出群落的综合生态特征。

The production and accumulation of propionic acid affect significantly anaerobic wastewater treatment system, but the reasons are not approached until now. Based on the results of continuous-flow tests and the analysis of biochemistry and ecology, two mechanisms of producing propionic acid have been put forward. It is demonstrated that the reasons of propionic acid production and accumulation are not caused by higher hydrogen partial pressure. The combination of specific pH value and ORP is the ecological factor affecting propionic acid production, and the equilibrium regulation of NADH/NAD+ ratio in cells is the physiological factor. Meanwhile, it is put forward that using the two-phase anaerobic treatment process and the ethanol type fermentation in anaerobic reactor to avoid propionic acid accumulation are efficient methods.

To improve the hydrogen evolution rate in continuous hydrogen production of a novel fermen-tative hydrogen-producing bacteria st rain B49 (AF481148 in EMBL), 4% immobilized cells by polyvinyl alcohol-boric acid method, with the addition of a small amount of calcium alginate in a column reactor obtain hydrogen yield of 2.31mol H2/mol glucose and hydrogen evolution rate of 1435.4ml/L culture•h respectively at medium retention time of 2.0h with a medium containing 10g glucose/L. Moreover, as the cell density in gel beads is increased to 8%, hydrogen yield and hydrogen evolution rate for 10g glucose/L are 2.34mol H2/mol glucose and 2912.4ml/L culture•h respectively at medium retention time of 1.0h, and for molasses wastewater COD of 7505.9mg/ L hydrogen production potential of 205.6ml/g COD and hydrogen evolution rate of 2057.7ml/L culture•h at hydraulic retention time of 0.75h are observed. In the continuous culture pH value keeps around 3.9 by self-regulating.