Metabolic flux network analysis of fermentative hydrogen production: Using Clostridium tyrobutyricum as an example

• Metabolic fluxes for C. tyrobutyricum in H2 production from glucose and lactate/acetate fermentation.
• MFA results indicate that HRT presents a significant impact on the flux of hydrogen production from glucose.
• At HRT between 4 and 18 h, increase of HRT increased hydrogen production but decreased lactate production.
• At HRT <4 h decrease of HRT increased hydrogen production but decreased lactate production.
• The flux for lactate, butyrate and acetate affects H2 production, due to their impacts on NADH, ferredoxin and ATP.

This study applies metabolic flux network analysis (MFA) to evaluate the metabolic flux of fermentative hydrogen production (FHP) with the use of Clostridium tyrobutyricum fed with either glucose or lactate/acetate as substrates. The MFA results suggest that hydraulic retention time (HRT) presents significant impact on hydrogen production from glucose. At HRT between 4 and 18 h, increase of HRT increased hydrogen production but decreased lactate production, while at HRT below 4 h decrease of HRT increased hydrogen production but decreased lactate production. The flux for lactate, butyrate and acetate seemed to affect H2 production, due presumably to their impacts on the balance of NADH, ferredoxin and ATP. It is suggested that the MFA can be a useful tool to provide valuable information for optimization and design of the fermentative hydrogen production process.