Use of different alkaline pretreatments and enzyme models to improve low-cost cellulosic biomass conversion

Two commonly alkaline pretreatment processes base on aqueous ammonia and lime under different enzyme hydrolysis models were evaluated to provide comparative sugar production performance from silvergrass, napiergrass and rice straw. The chemical composition variation of all biomass were nearly in stable after 4 weeks pretreatment under room temperature and recovery of the cellulose fraction was >90% by both pretreatment methods, the silvergrass recovered more dry matter than other biomass after pretreatment. Compared with other combination of pretreatment and enzyme model, mixed enzyme model after lime pretreatment significantly enhanced the biomass degradation especially in silvergrass and rice straw, but single enzyme supplement (cellulase or hemicellulase) result in limited sugar yield in this study. The biomass conversion result showed that considerable sugar yield from untreated napiergrass under the mixed enzyme model. However, alkaline pretreatment had no positive effect on glucose conversion from napiergrass. Increasing the mixed enzyme activity from 2.89 to 10.68 FPU g−1 improved the glucose yield from 3.4 to 4.4 times and from 2.8 to 3.3 times after ammonia and lime pretreatment, respectively. The findings of this study suggest that pretreatment methods and enzyme loading model should be considered simultaneously to enhance cellulosic biomass degradation. Furthermore, the pretreatment method should be applied according to the fiber composition of the biomass. The suitable pretreatment process and constituent of enzyme mixture for individual cellulosic biomass is a promising line of inquiry.

► The pretreatment method should be applied according to the fiber composition of the biomass. ► The mixed enzyme resulted in significant improvement of sugar yield from cellulosic biomass. ► The enzyme model and loading activity have to operate in coordination to improve the biomass degradation.