Effects of ph value on co-production of butanol and hydrogen by clostridium beijerinckii fermentation and kinetic modeling

The effects of pH value on co-production of butanol and hydrogen by fermentation with Clostridium beijerinckii IB4 were studied. The results demonstrated that both hydrogen and butanol fermentation was partially related to growth. When pH value was controlled at 6.0, cells grew well and hydrogen was accumulated rapidly during the initial fermentation phase (0~16 h). However, clostridial metabolism was inhibited by the accumulation of organic acids during later fermentation phase. When pH value was at lower value of 4.9, cells grew slowly and metabolic activities were restrained. When pH value was controlled at 5.2, butanol accumulation and hydrogen evolution achieved 12.06 g/L and 5.76 L/L, respectively, which were 11.87% and 15.43% higher than those without pH value control. The kinetic models on cell growth, butanol and hydrogen production in batch fermentation were established, the kinetic coefficient R² demonstrated the fitting of the models was good. Making comparison among kinetic parameters, constant coefficient, indication of butanol synthesis ability after cells growth ceased, was improved by 105.45%, and constant coefficient, indication of maximum hydrogen production rate was improved by 7.45%, when pH value was controlled at 5.2.