14-03: Extractive-AFEX (E-AFEXTM) pretreatment: a unified approach for resolving bottlenecks to efficient cellulosic bioethanol production

Current biorefining approaches present several bottlenecks that impact the economic viability of lignocellulose-derived fuels and chemicals. These include (i) minimization of enzyme requirements for biomass hydrolysis (<5 mg/g glucan), (ii) sugar yields above 85% at high solids loading (>6% glucan) and (iii) faster hydrolysis rates with minimal mass transfer limitations. Traditional chemical pretreatments, along with the latest generation of hydrolytic enzymes, have not yet satisfied these bottlenecks.

To address these bottlenecks, we have modified the traditional ammonia fiber expansion (AFEX^TM) pretreatment to convert native cellulose I to cellulose III while simultaneously delignifying the biomass. This new pretreatment is designated as Extractive-AFEX (or E-AFEX^TM). This novel pretreatment allowed at least fourfold reduction in enzyme loading while minimizing the solids effect typically noticed at high solids loading to achieve >90% hydrolysis yield. Moreover, this pretreatment greatly benefited rapid sugar fermentation, especially for consolidated bioprocessing (CBP) ethanologens. E-AFEX^TM pretreatment readily extracted lignin (~50% of original) from the biomass in its native state, which can be further processed to obtain value-added chemicals and materials. This novel processing methodology opens new avenues for ammonia-pretreatment based biorefineries, which allow fractionation of lignocellulosic biomass into lignin and carbohydrate rich fractions in an economical manner. These aromatic and carbohydrate fractions can be further processed to different fuels, materials and chemicals using desired catalytic or biocatalytic routes.