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 μg l -1 led to increases in hydrogen yield, maximum production rate, conversion efficiency, biomass yield and lactate removal. At 100Μg-Mo l -1, the maximum rate was 12.0 ml h -1 l -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. © 2011 Taylor & Francis.