Bio-Hydrogen Production From Anaerobic Fermentation By Mixed Bacteria Cultures

H₂is drawing increasing attention in the recent years, because it is aclean, environmentally friendly and renewable energy source. Compared withtraditional chemical method to produce hydrogen, biological hydrogentechnology from biomass conversion by using microorganisms is consideredas a promising route for hydrogen production.Several functional strains with capability of producing amylase,protease and lipase were obtained from activity sludge by high-flux screeningmethod. Strain A1and B1, which possess hydrogen-producing characteristic,belong to Bacillus sp. and Brevundimonas sp., respectively, identified via16SrDNA molecular biological protocol. To date Brevundimonas sp. haven’t beenreported for hydrogen production.A novel complex microorganism agent was developed to producehydrogen from renewable biomass by mixed cultures. The hydrogenproduction potential of the two wild strains from different carbohydrates wasinvestigated in this study. Effects of trace elements and substratepre-treatment on hydrogen production were evaluated. Then this microorganism agent was applied in the hydrogen production process fromcassava （non-grain crops） and sugar-containing wastewater. The substratedegration and hydrogen generation were modeled by first order reaction andGompertz equation respectively.It was found that this microorganism agent could use a wide range ofsubstrate, such as unhydrolyzed starch powder. Mixed cultures performedbetter than pure culture for hydrogen production, due to the positiveinteraction between the two strains. And its H₂yield was1.04mol H₂/molglucose, being twice higher than pure culture. H₂production can be largelyimproved by adding Fe²⁺or L-cysteine when starch is the substrate, whose H₂yields reach1.94mol H₂/mol glucose and1.53mol H₂/mol glucose,respectively. Substrate pre-treatment can accelerate the hydrogen productionprocess. Cassava is one of non-grain crops, which makes it a low costfeedstock to produce H₂. A maximum H₂yield of1.72mol H₂/mol glucosewas obtained under the optimum conditions. The hydrogen production abilityof carbohydrate-rich wastewater was3.2mol H₂/mol glucose. Substratedegration belongs to first order reaction with a correlation coefficient of0.8672. The hydrogen generation and VFAs production can be well fitted withGompertz equation. The correlation coefficient is between0.96and0.98.