title: Feasibility of biohydrogen production from industrial wastes using defined microbial co-culture.
abstract: BACKGROUND
  The development of clean or novel alternative energy has become a global trend that will shape the future of energy. In the present study, 3 microbial strains with different oxygen requirements, including Clostridium acetobutylicum ATCC 824, Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D, were used to construct a hydrogen production system that was composed of a mixed aerobic-facultative anaerobic-anaerobic consortium. The effects of metal ions, organic acids and carbohydrate substrates on this system were analyzed and compared using electrochemical and kinetic assays. It was then tested using small-scale experiments to evaluate its ability to convert starch in 5 L of organic wastewater into hydrogen. For the one-step biohydrogen production experiment, H1 medium (nutrient broth and potato dextrose broth) was mixed directly with GAM broth to generate H2 medium (H1 medium and GAM broth). Finally, Clostridium acetobutylicum ATCC 824, Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D of three species microbial co-culture to produce hydrogen under anaerobic conditions. For the two-step biohydrogen production experiment, the H1 medium, after cultured the microbial strains Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D, was centrifuged to remove the microbial cells and then mixed with GAM broth (H2 medium). Afterward, the bacterial strain Clostridium acetobutylicum ATCC 824 was inoculated into the H2 medium to produce hydrogen by anaerobic fermentation.
  
  
  RESULTS
  The experimental results demonstrated that the optimum conditions for the small-scale fermentative hydrogen production system were at pH 7.0, 35°C, a mixed medium, including H1 medium and H2 medium with 0.50 mol/L ferrous chloride, 0.50 mol/L magnesium sulfate, 0.50 mol/L potassium chloride, 1% w/v citric acid, 5% w/v fructose and 5% w/v glucose. The overall hydrogen production efficiency in the shake flask fermentation group was 33.7 mL/h(-1).L(-1), and those the two-step and the one-step processes of the small-scale fermentative hydrogen production system were 41.2 mL/h(-1).L(-1) and 35.1 mL/h(-1).L(-1), respectively.
  
  
  CONCLUSIONS
  Therefore, the results indicate that the hydrogen production efficiency of the two-step process is higher than that of the one-step process.
authors.affiliation: School of Pharmacy, Lanzhou University, Donggang West Road No. 199, Lanzhou, 730020, People's Republic of China. chenpeng@lzu.edu.cn.
authors.forename: Peng
authors.initials: P
authors.lastname: Chen
authors.affiliation: Key Laboratory of Fermentation Resources and Application of Institutes of Higher Learning in Sichuan, School of Life Science and Food Engineering, Institute for Bioengeering, Yibin University, Jiusheng Road No. 8, Yibin, 644000, People's Republic of China. wangyx0411@163.com.
authors.forename: Yuxia
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing, 163319, People's Republic of China. hekouyanlei@gmail.com.
authors.forename: Lei
authors.initials: L
authors.lastname: Yan
authors.affiliation: The Reproductive Medicine Research Center of the First Hospital of Lanzhou University, Donggang West Road No. 1, Lanzhou, 730020, People's Republic of China. 511508864@qq.com.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Gansu Institute of Business and Technology, Yannan Road No. 449, Lanzhou, 730010, People's Republic of China. lisuyue2014@163.com.
authors.forename: Suyue
authors.initials: S
authors.lastname: Li
authors.affiliation: Gansu Institute of Business and Technology, Yannan Road No. 449, Lanzhou, 730010, People's Republic of China. yan_xj@163.com.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Yan
authors.affiliation: Gansu Institute of Business and Technology, Yannan Road No. 449, Lanzhou, 730010, People's Republic of China. landa04@163.com.
authors.forename: Ningbo
authors.initials: N
authors.lastname: Wang
authors.affiliation: Gansu Institute of Business and Technology, Yannan Road No. 449, Lanzhou, 730010, People's Republic of China. gslz999@126.com.
authors.forename: Ning
authors.initials: N
authors.lastname: Liang
authors.affiliation: School of Pharmacy, Lanzhou University, Donggang West Road No. 199, Lanzhou, 730020, People's Republic of China. lihy@lzu.edu.cn.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Li
mesh_terms: D002264:Carboxylic Acids / Q000378:metabolism; D046969:Clostridium acetobutylicum / Q000378:metabolism; D018920:Coculture Techniques; D004553:Electric Conductivity; D016972:Enterobacter cloacae / Q000378:metabolism; D005240:Feasibility Studies; D005285:Fermentation / Q000502:physiology*; D006859:Hydrogen / Q000032:analysis / Q000378:metabolism*; D007220:Industrial Waste; D007477:Ions / Q000378:metabolism; D007716:Kluyveromyces / Q000378:metabolism; D008670:Metals / Q000378:metabolism; D059013:Microbial Consortia / Q000502:physiology*; D056265:Microbial Interactions / Q000502:physiology; D059205:Renewable Energy; D013213:Starch / Q000378:metabolism; D013997:Time Factors; D062065:Wastewater / Q000032:analysis
chemical_list: D002264:Carboxylic Acids; D006859:Hydrogen; D007220:Industrial Waste; D007477:Ions; D008670:Metals; D013213:Starch; D062065:Wastewater