The Production And Application Of Reducing Power In The Anaerobic Microorganism Systems

Organic matter is applied by anaerobic microbe as substrate for all the metabolic reactions in vivo. The REDOX reaction of organic matter is the essence of biochemical reactions in the anaerobic system. At present, many researchers have carried out a series of studies of the reducing power produced by anaerobe. The reductive degradation of some pollutants, the production of new electrical energy and the degradation of organic matter in water were included. Those studies have shown that the system of anaerobic microbial had a strong processing power and economic value. However, the mechanism in the system was not explained clearly. Therefore, this study attempted to explore the reaction mechanism and found the nature of law through scientific research systematically. The main research contents and research results are as follows:1.27strains of electrochemically active bacteria (EAB) were rapidly isolated and their capabilities of extracellular electron transfer were identified using a photometric method based on WO3nanoclusters. These strains caused color change of WO3from white to blue in a24-well agar plate within40h. Most of the isolated EAB strains belonged to the genera of Aeromonas and Shewanella. One isolate, Pantoea agglomerans S5-44, was identified as an EAB that can utilize acetate as the carbon source to produce electricity and reduce azo dyes under anaerobic conditions. The results confirmed the capability of P. agglomerans S5-44for extracellular electron transfer. The isolation of this acetate-utilizing, facultative EB A reveals the metabolic diversity of environmental bacteria. Such strains have great potential for environmental applications, especially at interfaces of aerobic and anaerobic environments, where acetate is the main available carbon source.2. The ratio of H2/acetate in glucose fermentation shall be equal or less than2. However, the ratio over2is found in the literature. Two possible reasons were proposed in this study:acetate oxidation or biomass growth via acetyl-CoA. In order to find out the right reason, glucose fermentation by Caldicellulosiruptor saccharolyticus was investigated. Under different glucose concentrations (1.0g/L,2.0g/L,3.5g/L and7.5g/L), the Optical Density (OD620) reached a maximum value of0.35,0.48,0.53and0.55, respectively. It was found that the ratios of H2/acetate under different glucose concentrations were all greater than2. When CH3-13COOH was added to the system,60%of CH3-13COOH was converted to isotope ethanol. About the same amount of13CO2(0.01mmol) was detected in both the control and isotopie experiments, illustrating acetate oxidation didn’t occur in this study. The corrected ratio of H2/acetate after the compensation from biomass growth was around2, demonstrating the biomass growth from acetyl-CoA was the right reason for the abnormal high ratio.3. It is worth to study the decolorization ability of C. saccharolyticus under the optimum growth temperature of70℃in thermal spring, for example. For the first time, this study demonstrated that C. saccharolyticus could effectively degrade methyl orange (MO) to4-aminobenzenesulfonic acid (4-ABA) and N’,N-dimethyl-p-phenylenediamine (DPD) with dissolved hydrogen (DH) as the reducing equivalent. The decolorization reaction was catalyzed by Ni-Fe hydrogenase. The reaction rate was positively related to the DH concentrations. For example, the decolorization rates were6.65and7.08mg/L/h at higher DH, but decreased to2.16and0.88mg/L/h after N2purging. Furthermore, the addition of MO in glucose fermentation decreased the ethanol yield due to the limited reducing equivalents. It could be conjectured that the competition for hydrogen between azo dyes reduction and hydrogenotrophic methanogenesis processes might also exist in mixed culture fermentation.4. This study focused on examining the general applicability of coupling bio-Pd nanoparticle generation and bio-H2produced by C. saccharolyticus for water treatment under extreme-thermophilic conditions. Palladium was added to cell cultures to achieve a final Pd concentration of50mg L-1. Methyl orange and diatrizoate were chosen as the contaminants in water. MO (100mg/L) was degraded within30min in the cultures with Pd added, while6hours were needed without Pd addition. Diatrizoate (20mg/L) was degraded within10min in Pd added cultures. However, diatrizoate was not degraded in the culture without Pd. The degradation rates were positively correlated with dissolved hydrogen generated by C. saccharolyticus. Furthermore, the catalytic actions of Pd(0) nanoparticle and cell were distinguished during the degradation process. And cells of C. saccharolyticus dispersed the Pd(0) particles well and showed a better catalytic activity than chemic-Pd(O) without dispersant. Dissolved hydrogen produced by C. saccharolyticus should be the perfect reduction equivalent for Pd formation. Generally speaking, the biodegradation proceeding with the action of in situ bio-H2in natural environment of high temperature should be illuminated.