Isolation And Functional Assessment Of An Anaerobic Xylose Fermentation Hydrogen Production Bacteria

Hydrogen is an ideal alternative energy, having the advantages of safety, low consumption, cheap, green. Lignocellulose is an importantraw materialin the process ofbiorefinery, with stable structure and difficult to conversion effectively. Xylose is the mean component of the lignocellulose hydrolysis, only when it turn into xylulose can microorganisms used it.Many bacterias do not have related enzymes, cause the low conversion efficiency of xylose. At present, the hydrogen production capacity is weak in most of the xylose fermentation hydrogen production bacteria. Above those problems, based on anaerobic degradation lignocellulose microorganism FSC which is enriched by our lab, using hungate anaerobic technology, we isolated and purified strain FSC-15 and analyzed the phylogenesis, physiological and biochemical characteristics, and hydrogen production capacity of it. Researched the Metabolites tolerance of the strain. Optimized hydrogen production conditions of strain FSC-15 by single factor and orthogonal experiment. Explored the influence of pentose, hexose, and mixed sugar to stain’s growth and hydrogen production. Estimated the change of methane yield of cellulose anaerobic degradation bacterials FSC after adding strain FSC-15 with filter paper and rice straw as substrates. The results are as follows:(1)Strain FSC-15 had a 99.6% 16 S r RNA gene sequence similarity to Clostridium dioils DSM 5431T(AJ458418) and Clostridium beijerinckii NCIMB 8052T(CP000721), but the physiological characteristics of the strain is closer to Clostridium beijerinckii NCIMB 8052T(CP000721). The optimum growth temperature is 35 ℃- 40 ℃, and the optimum growth p H 7.5. Strains can tolerate 1500 mg/L acetic acid, and 2000 mg/L butyric acid. 400 mg/L ethanol, the growth of bacteria and hydrogen production was reduced by 61.2% and 57.4% respectively. The growth of bacteria was inhibited by 19.8%, when initial hydrogen partial pressure reached 134.2 k Pa.(2)The optimum hydrogen production conditions of Strain FSC-15 was YE 0.1 g/L,BBL 0.1 g/L,NH4 Cl 1g/L,Na HCO3 0.8 g/L,Fe3+ 75 μmol/L,Ni2+ 5 μmol/L, and initial p H 7.5, temperature 40 ℃ by single factor and orthogonal experiments.(3)In mixed sugar fermentation systems, not only the strain grow faster, and biomass was increased significantly, the hydrogen yield was higher.With xylose and glucose as substrates respectively, there was no visible difference in growth rate. As time continue, hydrogen yield in xylose fermentation system was higher than the others. The maximum hydrogen yield was 1.845 mol H2/mol xylose and 1.179 mol H2/mol glucose.(4)2% Strain FSC-15 can improve 41.8% of the hydrogen yield of FSC. With rice straw as substrate, the methane production rate of FSC was increased obviously by co-culture with strain FSC-15, the methane yield improved for one time.There was no visible difference in cellulose degradation rate between co-culture and FSC. The specis and abundance of bacteria and archaea have been changed when strain FSC-15 added into FSC.