Biobutanol Production from Hexose and Pentose Sugars

The Acetone-Butanol-Ethanol (ABE) fermentation is receiving renewed interest as a way to upgrade renewable resources for the production of products with high added value as chemicals and fuels. Main pre-requisites of fermentation feedstocks are abundance and un-competitiveness with food sources and they are fulfilled by lignocellulosic biomass. This contribution reports about the characterization of the ABE fermentation by Clostridium acetobutylicum DSM 792 adopting sugars representative for hydrolysis products of lignocellulosic biomass: glucose, mannose, arabinose, and xylose. Batch fermentation tests with binary mixtures of sugars were performed to assess the possible crossed/coupled effects of the investigated sugars on the fermentation performances. The mass ratio of sugars in binary mixture tests was set at 1:1 and the total initial concentration was set at 60 g/L. The conversion process was characterized as a function of the time in terms of biomass, acids, and solvents concentrations as well as of pH and total organic compounds. The simultaneously fermentation of binary mixture of sugars enhances the conversion of the investigated sugars into butanol/solvents. The xylose fermentation appears to be improved when it is mixed with the investigated sugars.