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

Abstract

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 m3 reactor is reported. A detailed description of acetone-butanol production from corncob hydrolysates in 50 m3 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.