Abstract
The effects of C/N on mesophilic continuous hydrogen fermentation were investigated by varying C/N from 3 to 222. A total of 6 identical completely stirred tank reactors (CSTRs) were separately operated at each C/N. This study revealed that C/N is an important parameter for hydrogen fermentation. Suitable C/N values for mesophilic continuous hydrogen fermentation were between 3-22. When C/N was higher than 22, substrate degradation efficiency, bacterial growth and hydrogen yield were decreased, respectively. The stoichiometric equation of hydrogen fermentation at C/N 5 was expressed as follows: starch → 1.67n H2 + 1.31n CO2 + 0.76n butyrate + 0.54n acetate + 0.14n biomass (C5H8.42O2.98N0.99S0.02) . It was also indicated that part of the hydrogen produced was consumed by hydrogentrophic homoacetogenes.
