title: Effects of Mo(VI) on phototrophic hydrogen production by Rhodobacter sphaeroides.
abstract: Effects of Mo(6+) concentration on phototrophic hydrogen production of Rhodobacter sphaeroides were investigated using lactate as the sole carbon source. Results showed that an increase of Mo(6+) from nil to 1000 microg l(-1) led to increases in hydrogen yield, maximum production rate, conversion efficiency, biomass yield and lactate removal. At 100 microg-Mo l(-1), the maximum rate was 12.0 ml h(-1) with a conversion efficiency of 36.1%, the cell yields were 1.11 g-cell g(-1) -lactate and 2.4 g-cell g(-1)-TOC removed. Further increase of Mo(6+) improved hydrogen production only marginally. Degradation of lactate by R. sphaeroides produced not just hydrogen but also acetate, butyrate, i-valerate, i-caproate, hexanoate and some unidentified organic intermediates, but did not produce propionate and alcohols. Nitrogenase activity, as measured by the acetylene reduction method, had no clear correlation with either Mo(6+) concentration or hydrogen yield.
authors.affiliation: Centre for Environmental Engineering Research, Department of Civil Engineering, University of Hong Kong, Hong Kong, China. hrechef@hkucc.hku.hk
authors.forename: Herbert H P
authors.initials: HH
authors.lastname: Fang
authors.forename: Ru Ying
authors.initials: RY
authors.lastname: Li
authors.forename: Tong
authors.initials: T
authors.lastname: Zhang
mesh_terms: D001674:Bioelectric Energy Sources; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D002244:Carbon / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005285:Fermentation; D006859:Hydrogen / Q000032:analysis / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D008982:Molybdenum / Q000378:metabolism / Q000494:pharmacology*; D052817:Phototrophic Processes; D012242:Rhodobacter sphaeroides / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D019344:Lactic Acid; D002244:Carbon; D006859:Hydrogen; D008982:Molybdenum