Preliminary study on rubber wood fiber (Hevea brasiliensis) improvement by laccase

Abstract

Cellulose and lignin are the two most abundant polymers found in plant cells. Cellulose microfibrils provide mechanical properties to woody cell whereas, hemicelluloses and lignin act as glue in between the crystalline cellulose. Cellulose crystallinity directly affects the physico-chemical behavior of the individual fiber such as modulus, hardness, stiffness, tensile, and swelling-shrinkage properties and ultimately to its product. This work aimed to improve the physico-chemical properties of rubber wood fiber by laccase hydrolysis in order to improve the crystalline structure. Two different times of reactions i.e. 60 min and 120 min were applied at constant temperature 25°C, enzyme concentration 7 U/g and pH 5. After the pulp treatment, fibers were sieved out and transferred in to autoclave at 121°C for 15 min to stop further enzyme reaction. Treated fiber was dried in electric oven drier at 80-90°C for 24 hr to dry the fiber until zero moisture content. Crystallinity index of the fiber was measured by X-ray diffraction method and it was observed maximum up to 14% higher compared to untreated fiber. The treated fiber was further analyzed for elemental composition, FE-SEM, and TGA and compared with untreated fiber in order to evaluate its properties. Fiber treated with enzyme exhibited superiority in fiber surface structure and thermal degradation over untreated fibers. A fiber with improved mechanical strength and crystalline structure can be utilized for various purposes to produce high quality product.