Microbial Fermentative Hydrogen Production And Its Medium Optimization Study

Hydrogen energy is clean and sustainable among the varied forms of fossil fuel such as coal,petroleum,natural gas,etc.,which in some extent holds the promise as a dream fuel of the future all over the world with many social,economic and environmental benefits to its credit.Bioconversion is an ideal technology for hydrogen production,which is carried out by the anaerobic bacteria and the organic waste water or the solid waste is touted as the substrate. As the whole process can perform well at an ambient temperature and pressure,regardless of light and other factors,it is easier to be scaled up and even for the industrialization than other hydrogen production technologies.The study of the biohydrogen anaerobic fermentation technology,mainly focuses on the details of hydrogen production bacteria screening and the hydrogen production process optimization.Five kinds of different sludge are chosen for the anaerobic gradient acclimatization initially.Sample C,whose biohydrogen production capacity and flocculation ratio are 1.55 mol H₂/(g glucose) and 54.6%respectively,is the best of all.Furthermore,the kinetics model is constructed for evaluation.In addition,some preliminary investigations are carried on for the evolutions of bacterial structure during acclimation,which provides the for bacteria screening.Hungate technique,which is in widespread use,is adopted in this study.Five strains with the best efficiency are obtained among those eleven hydrogen production strains by screening. FML-C₁ is the best of the five,the hydrogen volume and the bioconversion of which reaches 1032.3 mL H₂/L culture and 0.83 tool H₂/(mol glucose) respectively prior to optimization. Since the analysis of its morphology,physiology and 16S rDNA gene sequence,and the BLAST result shows the gene is 99%homologous to Enterobaeter sp.12-1,the strain is denominated as Enterobacter FML-C₁ and it status in microbial taxonomy is then determined.Planckett-Burman design is widespread used in picking out the factors,including glucose, citric buffer and reducing agent,which have significant influences on H₂-production.Further experiment is designed by Central Composite Design(DDC) and analyzed by Response Surface Methodology(RSM).The optimal condition is 21.5 g/L glucose,13.6 mL/L citric buffer and 10.0 mL/L reducing agent.The biohydrogen production reaches 2347.4 mL H₂/(L culture) and the bioconversion is 1.11 mol H₂/(mol glucose),which are 127.42%and 33.74% respectively increased compared to the previous result.