Large-scale enzymatic hydrolysis of agricultural lignocellulosic biomass. Part 2: Conversion into acetone-butanol

Large-scale development of a process for conversion of lignocellulosic biomass into acetone-butanol involving steam-explosion pretreatment of the raw material cellulase production, enzymatic hydrolysis of pretreated material and acetone-butanol fermentation of hydrolysates has been carried out in the facilities for biomass conversion located at Soustons, France. Procedures and scale-up of the two steps of enzymatic hydrolysis and fermentation using corncobs the raw material, cellulase production, enzymatic Clostridium acetobutylicum strain capable of a good utilization of xylose and presenting a limited sensitivity to the fermentation inhibitors orginating from the steam-explosion pretreatment is described. Optimization of acetone-butanol fermentation involved, in particular, the definition of a suitable inoculum transfer chain for fermenting untreated hydrolysates. Batch enzymatic hydrolysis of pretreated corncobs at the scale of the 25 m 3 reactor is reported. A detailed description of acetone-butanol production from corncob hydrolysates in 50 m 3 fermenters is presented. Based on the mass balances and performances of the individual steps, economic aspects of the conversion of lignocellulosic biomass by hydrolysis and fermentation are discussed.