Effects of Alkali Treatment on Component and Structure and Enzyme Saccharifying Efficiency of Sweet Sorghum Bagasse

Abstract

Sweet sorghum variety M81 was used as the experimental material, the sweet sorghum bagasse(SSB) was treated under four conditions(lime at room temperature, lime with microwave treatment, lime with autoclave treatment and sodium hydroxide at room temperature) with the washed and untreated SSB as control. The changes of lignocellulose structure and the cellulase saccharifying efficiency of SSB under different conditions were investigated. The results showed that four treatments effectively changed the lignocellulose component of sweet sorghum bagasse, especially in the case pretreated by sodium hydroxide under room temperature for two weeks, and lime played an important role in hemicellulose dissolution too. Scanning electron microscopy(SEM) observation indicated that the lignocellulose structure was different in two treatments of lime with autoclave treatment and sodium hydroxide at room temperature. The surface of lignin in the treatment of lime and autoclave was eroded seriously and its fragments adhered to the surface of cellulose, but the internal fiber structure still arranged tightly; in the treatment of NaOH at room temperature the lignocellulose beam structure was swelled and degraded, and the cellulose fiber net appeared due to the surface component of lignin removed a lot and many small holes appeared. By using the four pretreated methods, the cellulose and hemicellulose of sweet sorghum bagasse were enzymatically saccharified, the concentrations of glucose and xylose increased 1.5, 2.1, 1.9, 4.2 times and 3.1, 5.0, 4.9, 2.4 times, respectively as compared with the control. The direct conversion rate and the relative conversion rate of cellulose and hemicellulose are different, but have a significant guiding function for the choose of treatment methods and the effect of comprehensive evaluation, in addition, also an instructive function for the breeding and cultivating of sweet sorghum with high yield and good energy productive factors in the practical production.