EFFECT OF VARIOUS HYDROTHERMAL PRETREATMENTS ON COMPOSITION,STRUCTURE AND ENZYMATIC HYDROLYSIS OF RICE STRAW
To investigate the effects and mechanisms of various hydrothermal pretreatment on the physicochemical structure,chemical composition and enzymatic hydrolysis of rice straw,four pretreatment methods,pure hydrothermal,KOH,CH3COOH,HCl and FeCl2,were all used to treat rice straw.The material loss,chemical composition,specific surface area,pore structure,chemical structure,roughness,particle size,and changes in sugar concentration after enzymatic hydrolysis were explored.The results showed that alkaline-thermal pretreatment could effectively remove the lignin from the straw by breaking the ester bond,and the lignin recovery rate decreased to 46.2%.Furthermore,the dissolution of the lignin caused a severe collapse of the internal structure of the straw.The relative crystallinity increased significantly by 38.9%,and the pore size decreased to 9.24 mm,while the surface area decreased to 2.62 m2/g.Acid treatment had a greater impact on the dissolution of hemicellulose,leading to the formation of more small pores and micropores in the straw.After alkaline-thermal pretreatment,the straw particle size was reduced from 0.334 mm to 0.141 mm,and the fractal dimension decreased from 1.92 to 1.71.The loose structure improved the efficiency of the enzymatic hydrolysis reaction.Total sugar concentration reached 39.9 g/L,mainly consisting of glucose and xylose.The highest glucose content was found in the pretreated HCl group.