8-39: Enzymatic hydrolysis of steam exploded cereal straw at high solid loading

In the conversion of lignocellulosic biomass to ethanol, process yield depends largely on the efficiency of conversion of glucans and xylans to fermentable sugars through the steps of pretreatment and enzymatic hydrolysis. For industrial application of the technology it is necessary to attain ethanol concentrations in fermentation that make distillation step feasible from an economical point of view, which implies the use of high solid loadings in enzymatic hydrolysis and fermentation.

 Wheat straw is an important residue from grain industry in Spain that is being investigated as substrate for bioconversion to fuel ethanol. Although significant advances have been attained in the conversion process of this feedstock to ethanol through hydrothermal pretreatments, enzymatic hydrolysis and fermentation, process performance at high solid consistency is still a challenge.

The aim of this work was to investigate the best reaction conditions for enzymatic hydrolysis of steam exploded wheat straw biomass at high pretreated solid loading. Steam explosion pretreatment of wheat straw was performed in a 2 L batch pilot unit at selected conditions of 210ºC and 5 min. After pretreatment, the slurry was filtrated and separated into a solid and liquid fraction. The pretreated water insoluble solid fraction (WIS) was tested for enzymatic hydrolysis in laboratory experiments at 20% (w/w) WIS consistency using commercial cellulases and hemicellulases under different reaction configurations. The effect of enzyme dosing timing, reaction temperature and the addition of surfactant on enzymatic saccharification yield was evaluated. Detailed results of this study will be presented.

Acknowledgements:  This work has been partially funded by the Regional Government of Madrid under the R&D Technology Programme/2009 (Project Ref. nº P2009/ENE-1743)