Effect of iron concentration on hydrogen fermentation

Abstract

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 mg FeCl 2 l −1 . The temperature was maintained at 37°C. The maximum specific hydrogen production rate was found to be 24.0 ml g −1 VSS h −1 at 4000 mg FeCl 2 l −1 . The specific production rate of butyrate increased with increasing iron concentration from 0 to 20 mg FeCl 2 l −1 , and decreased with increasing iron concentration from 20 to 4000 mg FeCl 2 l −1 . The maximum specific production rates of ethanol (682 mg g −1 VSS h −1) and butanol (47.0 mg g −1 VSS h −1) were obtained at iron concentrations of 5 and 3 mg FeCl 2 l −1 , respectively. The maximum hydrogen production yield of 131.9 ml g −1 sucrose was obtained at the iron concentration of 800 mg FeCl 2 l −1 . The maximum yields of acetate (389.3 mg g −1 sucrose), propionate (37.8 mg g −1 sucrose), and butyrate (196.5 mg g −1 sucros) were obtained at iron concentrations of 3, 200 and 200 mg FeCl 2 l −1 , respectively. The sucrose degradation efficiencies were close to 1.0 when iron concentrations were between 200 and 800 mg FeCl 2 l −1 . The maximum biomass production yield was 0.283 g VSS g −1 sucrose at an iron concentration of 3000 mg FeCl 2 l −1 .