Substrate Dependency and Effect of XylanaseSupplementation on Enzymatic Hydrolysisof Ammonia-Treated Biomass

摘要

Pretreatment based on aqueous ammonia was investigated under two differentmodes of operation: soaking in aqueous ammonia and ammonia recycle percolation. Theseprocesses were applied to three different feedstocks with varied composition: corn stover, highlignin (HL), and low lignin (LL) hybrid poplars. One of the important features of ammonia-based pretreatment is that most of the hemicellulose is retained after treatment, which simplifiesthe overall bioconversion process and enhances the conversion efficiency. The pretreatmentprocesses were optimized for these feedstocks, taking carbohydrate retention as well as sugaryield in consideration. The data indicate that hybrid poplar is more difficult to treat than cornstover, thus, requires more severe conditions. On the other hand, hybrid poplar has a beneficialproperty that it retains most of the hemicellulose after pretreatment. To enhance the digestibilityof ammonia-treated poplars, xylanase was supplemented during enzymatic hydrolysis. Becauseof high retention of hemicellulose in treated hybrid poplar, xylanase supplementationsignificantly improved xylan as well as glucan digestibility. Of the three feedstocks, bestresults and highest improvement by xylanase addition was observed with LL hybrid poplar,showing 90% of overall sugar yield.