High Solids Loading Pretreatment and Whole Slurry Saccharification and Ethanol Fermentation of Rice Straw

In cellulosic ethanol production, the solids loading ratio of biomass in pretreatment and saccharification are closely related to the final ethanol titer and production cost. In this study, pretreatment of rice straw at a high solids loading (20%, w/v) using maleic acid as a catalyst was investigated. The optimized conditions for pretreatment were 190°C with 0.2% or 5% (w/v) maleic acid for 20 min. The enzymatic digestibilities (based on theoretical glucose yield) of cellulose in the optimally pretreated rice straw was over 80%. When saccharification and fermentation of whole slurry of pretreated rice straw was performed in the presence of activated carbon to eliminate inhibitory compounds in the pretreatment slurry, a 62.8% final yield of ethanol based on the initial glucan in unpretreated rice straw was obtained. Our findings indicate that lignocellulose pretreated at a high solids loading using maleic acid can be applied to SSF of the whole slurry of pretreated rice straw to eliminate the solid/liquid separation after pretreatment and before SSF. These results could eventually be contributed to developing economically-feasible cellulosic fuel production processes.