Effect of kraft pulping pretreatment on the chemical composition, enzymatic digestibility, and sugar release of moso bamboo residues

Abstract

In this work, kraft pulping was carried out on moso bamboo residues as a pretreatment and its impact on the chemical compositions and the digestibility of the sample was investigated. Meanwhile, steam explosion and sulfuric acid pretreatments were also carried out on the sample to determine their impacts on enzymatic saccharification. Results showed that kraft pulping pretreatment removed a significant amount of lignin from the sample, and its enzymatic saccharification was enhanced. Approximately 95% of the lignin was removed with the optimized kraft pulping pretreatment (26% effective alkali charge, 24% sulfidity, 160 °C, and 70 min cooking time). Consequently, about 79% and 77% yields of glucan and xylan, respectively, were achieved with enzymatic saccharification from the pretreated sample. As a result, 352 g, 128 g, and 88 g sugars were generated from 1000 g of samples pretreated by kraft pulping, steam explosion, and sulfuric acid, respectively. The results suggested that kraft pulping can be a remarkably effective pretreatment applied on moso bamboo residues (i.e., lignin-rich biomass) for sugars released, compared to steam explosion and sulfuric acid pretreatment.