Impact of Alkaline Pretreatment Condition on Enzymatic Hydrolysis of Sugarcane Bagasse and Pretreatment Cost

Abstract

A combined severity factor (R_CSF) which is usually used to evaluate the effectiveness of hydrothermal pretreatment at above 100 °C had been developed to assess the influence of temperature, time, and alkali loading on pretreatment and enzymatic hydrolysis of lignocellulose. It is not suitable for evaluating alkaline pretreatment effectiveness at lower than 100 °C. According to the reported deducing process, this study modified the expression of ${R}_{\mathrm{CSF}}=\log \left[{C}_{OH^{-}}^n\times t\times {e}^{\left({T}_r-{T}_b\right)/14.75}\right]$ as ${R}_{\mathrm{CSF}}=\log \left\{{C}_{OH^{-}}\times t\times {e}^{\left[-13700/\left( Tr+273\right)+36.2\right]}\right\}$ which is easier and more reasonable to assess the effectiveness of alkaline pretreatment. It showed that R_CSF exhibited linear trend with lignin removal, and quadratic curve relation with enzymatic hydrolysis efficiency (EHE) at the same temperature. The EHE of alkali-treated SCB could attain the maximum value at lower R_CSF, which indicated that it was not necessary to continuously enhance strength of alkaline pretreatment for improving EHE. Within a certain temperature range, the alkali loading was more important than temperature and time to influence pretreatment effectiveness and EHE. Furthermore, the contribution of temperature, time, and alkali loading to pretreatment cost which was seldom concerned was investigated in this work. The alkali loading contributed more than 70% to the pretreatment cost. This study laid the foundation of further optimizing alkaline pretreatment to reduce cost for its practical application.