The Influencing Factors In Hydrogen Production And Metabolic Characteristics Of Clostridium Butyricum

Anaerobic fermentation biological hydrogen production technology can use organic wastewater or biomass as substrates and produce hydrogen through microbial fermentation metabolism,which can not only realize waste recycling,but also reduce the cost of hydrogen production.It is one of the research hotspots in the field of environmental protection and energy in recent years.Hydrogen-producing bacteria is one of the important components of anaerobic fermentation biological hydrogen production technology.The isolation and identification of high-efficiency hydrogen-producing bacteria and the study on the influencing factors of hydrogen production are of great significance to understand the physiological and biochemical characteristics of hydrogen-producing bacteria and improve the efficiency of hydrogen production,which is the basis of solving the industrialization of anaerobic fermentation biological hydrogen production.In this study,the modified Hungate anaerobic culture technology was used to isolate a strain with high efficiency hydrogen production performance,named YM-83,from a CSTR anaerobic fermentation reactor with high concentration molasses wastewater as the fermentation substrate.LM-1 medium was used for batch experiment.After continuous culture for 30 h,the maximum hydrogen production per unit volume was 4,858 m L/L culture,and the specific hydrogen production rate was1.94 mol H2/mol glucose.16 S r DNA analysis showed that the strain had 100%homology with Clostridium butyricum JCM 7840 gene sequence.Based on physiological and biochemical,morphological and systematic evolutionary analysis,hydrogen producing strain YM-83 was identified as Clostridium butyricum.The effects of various factors on the growth and hydrogen production of C.butyricum YM-83 were studied by intermittent experiments.The results showed that the optimum growth and hydrogen production temperature were 35℃.The initial p H of optimal growth and hydrogen production was 6.5.When the initial glucose concentration is 18 g/L,C.butyricum YM-83 has the best hydrogen productioncapacity.L-cys was beneficial to the growth and production of hydrogen by fermentation of C.butyricum YM-83.Based on the specific hydrogen production rate and economic considerations of the strain,the optimal concentration of L-cys was determined to be 0.5 g/L.The optimum growth and hydrogen-producing concentration of Mg Cl2·6H2O were 0.15 g/L.Among the three iron types,the promoting effect on hydrogen production of C.butyricum YM-83 was Fe2+ >Fe3+ >Fe.The optimal growth and hydrogen-producing Fe Cl2·7H2O concentration of C.butyricum YM-83 were 0.2 g/L.After determining the influence of various factors on C.butyricum YM-83,the optimal culture conditions were selected for intermittent experiment.After continuous culture for 36 h,the maximum unit volume gas production was 9,168 m L/L culture,the maximum unit volume hydrogen production was 5,360 m L/L culture,the specific hydrogen production rate was 2.15 mol H2/mol glucose,and the maximum cell dry weight was 1.04 g/L.Hydrogen production increased by 1.11 times compared with the initial screening.Under the condition that the initial p H of the medium was 6.5 and 7.5,the hydrogen production of C.butyricum YM-83 was measured by intermittent experiment,and the bacteria were collected at 30 h for metabolomics study.According to the results of metabolomics analysis,a total of 106 different metabolites were detected under the initial p H of 6.5 and 7.5,among which the contents of Dimethyluric acid and Nicotinic acid were significantly decreased.The contents of104 substances including L-lactic acid,D-ribose-5-phosphate,L-proline,L-histidine,Guanosine,Octadecylglycerol and Serotonin were significantly increased.Differential metabolites were mainly concentrated in Glutathione metabolism,Carbon metabolism,ABC transporters,Galactose metabolism,Biosynthesis of amino acids,Fructose and mannose metabolism,Lysine degradation,Biofilm formation-Escherichia coil,Glyoxylate and dicarboxylate metabolism and Methane metabolism.To sum up,the initial p H value of different medium had a significant effect on hydrogen production capacity and metabolism of C.butyricum YM-83.