Poplar (Populus deltoides L.): The Effect of Washing Pretreated Biomass on Enzymatic Hydrolysis and Fermentation to Ethanol

Abstract

In this work, Populus deltoides L. biomass was pretreated in 0.98% (v/v) sulfuric acid at 140 °C for 40 min. Prior to enzymatic hydrolysis, pretreated biomass was either not washed or washed with 1.5 or 3 volumes of water, as compared to biomass. Rinsing the pretreated biomass with 1.5 or 3 volumes of water resulted in glucose yields that were seven times greater than the nonwashed treatment. Pretreatment hydrolyzates, wash waters, and enzymatic hydrolysis hydrolyzates were analyzed for carbohydrate, aliphatic acid, aldehyde, and phenolic content. An analysis of the wash waters showed the presence of gallic, vanillic, syringic, p-coumaric, ferrulic, trans-cinnamic, and salicylic acids at concentrations below 0.07 mg mL–1. Washed and nonwashed enzymatic hydrolyzates showed significant differences in gallic, vanillic, ferrulic, and salicylic acid concentrations, indicating that these compounds could be in part responsible for inhibiting enzymatic hydrolysis. Nonwashed and washed enzymatic hydrolysates were ...