Rapid Screening Of Thermophilic Anaerobic Hydrogen-producing Bacteria And Study Of Fermentation Characteristics

With the continuous development of science and technology, people’s living standards improved and more and more people payed attention on the Energy and environmental issues. Since the beginning of the21st century, the contradiction between the rapid demanded growth of oil and other non-renewable fossil resource consumption and the sharp decline of oil production became more significant, So the world will face enormous energy challenges.Biomass energy as the largest output of renewable resources-widely distributed on the Earth, is value by the worldwide; The major component of biomass energy were the crops straw, so most of the biomass utilization research for was the comprehensive utilization of the crop straw; There are many ways of utilizing the straw in the world, and the most important research directions is for the energy conversion of straw, for example, transformed into electricity, heat, etc. Biological hydrogen production with its high conversion efficiency, low pollution and other properties will naturally become the research hotspot.Hydrogen as a flammable gas, has zero pollution, high combustion value and other many advantages which get lots of the new energy research focuses; The hydrogen production by anaerobic hydrogen producing bacteria, can not only make extensive use of a variety of biomass energy, but also perform simple operation, obtain high efficiencies in the hydrogen production process, which can be widely used in industrial production with the continuitied operation.This research used hydrogen producing bacteria flora isolated in the Changbai Mountain Hot Springs to study rapid screening methods of the thermophilic anaerobic gas-producing bacteria, Experimental results showed that bubble method could quickly isolate the high-temperature gas bacteria flora in the flask with80mL culture, in the specific gel concentrations, Then the hungate anaerobic technology was used for geting a single high-temperature gas-producing bacteria.The optimum temperature of the bacteria flora was75℃, the optimum pH was7.5, through the growth characteristics study, The high salt tolerance of the bacteria flora can be used in study of continuous production of hydrogen; This bacteria flora could be used for the processing of a variety of complex substances because it could use a variety of carbon sources as substrate for fermentation hydrogen production.On the choice of sulfur, the floras were very sensitive. In the case of sulfur are missing or inadequate in the bacterial growth environment, the flora could not grow well and produce hydrogen, since the sulfur compounds was of certain requirement, the optimum sulfur source were Na2S and Na2S2O3.In the fermentative hydrogen production experiment, the resulting hydrogen conversion rate was1.8molH2/mol glucose and H2production rate was180mL/L·h, with glucose as substrate, the optimal temperature, the optimal pH, indicating that the flora transformed most of glucose to H2,and could be used in the further fermentation studies.When the fermentation conditions were of low cellulose0.5%content, the hydrogen conversion rate was7.5mol H2/g VS. When the pH is6.99, the biggest H2production rate was101mlH2/L·h. This ideal experimental result showed that the feasibility using this flora to prepare of the biomass containing a large amount of cellulose material.When the fermentation conditions wasl.5%cellulose content, the fermentation by-products transformed from acetic acid into lactic acid, due to changes in the physiological metabolic pathways of bacteria. The lactic acid had significant toxic effects on bacterial growth. And the lactic acid accumulation led to the rapid decrease of pH in fermentation broth. The bacteria can not normally growthed; In this cellulose content is, even the pH stability of the fermentation broth was maintained in the optimal range, the fermentation would stop due to the accumulation of large amounts of lactic acid. Thus when this flora was applied to prepare biomass feedstock, the best way was to carried out in the continuous fermentation with low content of the substrate.In addition, through the use of paper processing sludge as substrate fermentation tests, get the better test results witch the total amount of fermentation gas was6016mL and the optimum fermentation time interval, the average gas production rate can be achieved175mL/L·h. Thus proving the mixed flora has a very broad application prospects.