Effect of iron concentration on hydrogen fermentation

The effect of the iron concentration in the external environment on hydrogen production was studied using sucrose solution and the mixed microorganisms from a soybean-meal silo. The iron concentration ranged from 0 to 4000 mgFeCl2 l−1. The temperature was maintained at 37°C. The maximum specific hydrogen production rate was found to be 24.0 mlg−1 VSSh−1 at 4000 mgFeCl2 l−1. The specific production rate of butyrate increased with increasing iron concentration from 0 to 20 mgFeCl2 l−1, and decreased with increasing iron concentration from 20 to 4000 mgFeCl2 l−1. The maximum specific production rates of ethanol (682 mgg−1 VSSh−1) and butanol (47.0 mgg−1 VSSh−1) were obtained at iron concentrations of 5 and 3 mgFeCl2 l−1, respectively. The maximum hydrogen production yield of 131.9 mlg−1 sucrose was obtained at the iron concentration of 800 mgFeCl2 l−1. The maximum yields of acetate (389.3 mgg−1 sucrose), propionate (37.8 mgg−1 sucrose), and butyrate (196.5 mg g−1 sucros) were obtained at iron concentrations of 3, 200 and 200 mgFeCl2 l−1, respectively. The sucrose degradation efficiencies were close to 1.0 when iron concentrations were between 200 and 800 mgFeCl2 l−1. The maximum biomass production yield was 0.283 gVSSg−1 sucrose at an iron concentration of 3000 mgFeCl2 l−1.