Effect of autohydrolysis pretreatment on rice straw for sugar production

Abstract

Rice straw is one of the agriculture by-product in Malaysia. In this study, the rice straw was used to undergo pre-treatment to synthesize sugar. The rice straw was physically pretreated using grinder and it was sieved. The lignocellulosic material then was autohydrolysis pretreated to remove hemicellulose and to breakdown the lignin structure, thus, the lignocellulosic biomass will breaks down into its sugars monomers by using liquid hot water and steam treatment. Liquid hot water was treated where the rice straw was directly contact with water in reactor with optimize two parameter in range 150˚C -210˚C and 5 min to 15 min. Whereas, steam treatment was treated by adding rice straw into steam stand before added into reactor contain water. It also optimize at temperature 150˚C -210˚C and 5 min- 15 min in range. The pretreated biomass then will undergo enzymatic saccharification to increase sugar yield by using cellulase enzyme. Rice straw has been observed by Scanning Electron Microscopy (SEM) and Fourier Transformed Infrared (FTIR) to shows the significant changes on ultrastructural and functional group after pretreatment. The result indicated that pretreatment had enhance the rice straw structure for enzymatic hydrolysis to produce maximum reducing sugar. This causing the partial decrystallization of cellulose, hemicellulose and degradation of ester and glycosidic side chains of rice straw structure. Parameters of pretreatment were optimized using Central Composite Design for Response Surface Methodology by setting temperature range 150˚C -210˚C and pretreatment time in range 5min - 15min. Seventeen runs of experiment were performed to study the effect of these parameters on reducing sugar production. Reducing sugar was enhance from 6.876 g/g to 15.705 g/g for liquid hot water and 0.855g/g to 0.9513 g/g for steam treatment. Hence, the liquid hot water is most preferred pretreatment for this project since, it shows the higher sugar production.