Co-fermentation of alfalfa juice and hardwood hydrolysate for butanol production in combined biorefinery systems

• The combination of alfalfa juice and FHWH for the production of ABE has been reported for the first time.
• The control of pH enhanced butanol production when xylose or FHWH were used as carbon sources.
• 3.80 g/L of ABE were obtained when mixing FHWH and alfalfa juice.
• The combination of wood and agricultural biomass is a viable substrate for ABE production.

In this study, a new fermentation medium combining a flocculated hemicellulosic wood hydrolysate (FHWH), rich in carbohydrates, obtained from a pulp and paper mill and an alfalfa juice, rich in nitrogen was used to produce butanol by Clostridium acetobutylicum ATCC 842. It was demonstrated that pH control enhances solvent production. The culture containing the two renewable biomass resources resulted in the production of 3.80 g/L of acetone-butanol-ethanol (ABE) with a productivity of 0.03 g/L h and a yield of 0.14 g/g. The obtained results demonstrated that the proposed combination can be used as a new fermentation medium for ABE production. However, the complexity of the medium induced an inhibitory effect and a decrease in the production of ABE, compared to the fermentation of FHWH and yeast extract.