Research Of Microbial Community Ecology And The Trophic Link During Acidogenic Fermentation

Acidogenic fermentation is a critical step in the process of anaerobicfermentation of organic matter. Volatile organic acids (VAFAs) is not only one of themain intermediate product, but also an important raw material for the organicchemical industry. Prductions of VAFAs is closely contact with organic matterdegradation and biogas generation. Hydrolysis microorganisms&acidogenicmicroorganisms, methane-producing microorganisms&VFAs-producingmicroorganisms have complex mutual camps relations. In recent years,high-throughput sequencing technology has been used by a growing number ofmicro-organisms workers and has been a very promising biotechnology. Unliketraditional sequencing methods with nucleotide specificity of the DNA fragments,high-throughput sequencing technology can parallel sequence to hundreds ofthousands to millions of DNA molecules. In VFAs-producing reactor, VFAs-producing microorganism population ecology was study. The methanogenicinhibitor addtion which does not affect the acid-producing microorganisms, volatilefatty acids and other intermediate metabolites is a common technique method.For our study, VFAs-producing microorganisms from the population andcommunity levels in the anaerobic fermentation was used by environment molecularmicrobial ecology technology, such as high-throughput sequencing, the populationstructure of the VFAs-producing bacteria was determined, the contribution ofvarious flora acetic acid was clarified, the yield of VFAs production was enhancedby flora structure and regulation. On these basis the optimal operating conditions ofthe process was identified, and a dynamic model was constructed. This study shouldenrich the theory and application of the anaerobic fermentation process.. The mainfindings are as follows:1Glucose-degrading microorganisms in activated sludge under methanogenicconditionsMonosaccharide degradation is an important step in the anaerobic fermentationof organic matter, the case for BES inhibition of methanogenesis, anaerobic sludgeglucose degradation plays a critical role in microbial less. The modes of anaerobicacid production and the production of methane was studied by DNA-SIP, clonelibrary and high-throughput sequencing technology, The results showed thatClostridia was dominant in the inhibition of methane-producing anaerobic fermentation, whose abundance accounted for51.88%of the total bacteria andBacilli was dominant in the inhibition of methanogenic anaerobic fermentation,whose abundance accounted for50%; The abundance of Peptococcaceae,Syntrophomonadaceae and Syntrophobacterale genus in the methanogenic culture issignificantly larger than the culture of inhibit methanogenis. The trophic linkbetween hydrogen-producing acetogenic bacteria and methanogenic bacteria p lay animportant role in anaerobic methane-producing system.2Trophic link between syntrophic acetogens and homoacetogensIn the anaerobic system, strengthen acetogenic reaction. by adding formate cansignificantly improve the activity of the hydrogen-producing process. Isotypeproducing acetic acid of the Gibbs free energy is reduced to-15KJ/mol, the sametype of acetogenic bacteria count was significantly greater than the other reactor; thepresence of acetic acid bacteria of the same type of production to "pull" thehydrogen production process, but this trophic link is limited. In the system of H2pressure was3.2KPa, butyric acid was4g/L and acetic acid was6g/L, the Gibbsfree energy reaches a critical value, the trophic link between syntrophic acetogensand homoacetogens was stopped; The acetate can be producted by the syntrophicacetogens/homoacetogens synergism and the proportion of acetate producted bysyntrophic acetogens and homoacetogens is7:33Acidogenic microbial ecology in the enrichment ofHomoacetogens was enriched by selective culture. At the same time, organicacids, the headspace gas and the activities of key enzymes was detected in theculture process. Homoacetogens was identified by compared the high-throughputsequencing at the befor and after enrichment and Firmicutes and Proteobacteriaaccounted for32.3%and42.9%respectively. Clostridium of the enriched sludgerepresent41.3%of the total bacteria. Archaea in original sludge was found (47OTU)and does not detected in enrichment sludge.4Conditions optimization to the system of homoacetogens enrichmentThe single-factor experiments were conducted to study the effects of substrateconcentrations, sludge concentration and pH value conditions in the enrichment ofhomoacetogens. The distribution of organic acid and the accumulation of acetic acidin the anaerobic fermentation process was studied. The results showed that thealkaline conditions conducive to the production of acetic acid, but hydrogenproduction bacteria, especially butyric acid degrading bacteria was inhibited.Production of hydrogen production bacteria and homoacetogens was widely present at just6days, and propionic and butyric acid degrading bacteria reaction was notactually the same at different pH conditions; The concentration of substrate was sohigh that the trophic link between syntrophic acetogens and homoacetogens issuppressed.5The kinetic model of the system of homoacetogens enrichmentThe kinetic model of homoacetogens enrichment based on ADM1model wasbuilded and the kinetic model was simulated and verified to experimental data. Theresult showed that the this model can be used as the basis to design the process ofhomoacetogens enrichment.