Enzymatic hydrolysis of treated palm oil empty fruit bunches fibre (EFB) using combination alkali-microwave techniques

Abstract

Combination of alkali-microwave pre-treatment on empty fruit bunches (EFB) fibre changed the morphology and properties of the EFB fibre as observed through scanning electron microscope (SEM) and Fourier transformed infrared spectroscopy (FT-IR). Pre-treatment process raptures the lignin and hemicellulose component inside the fibre, thus leaving available cellulose for hydrolysis process (Vlasenko et al., 1996). Most of the silica component and any impurities on the surface of the raw EFB fibre were removed during pre-treatment process, leaving an empty cauldron on the treated EFB surface. Furthermore, an internal structure of pre-treated EFB fibre showed a clear macrofibril compared to the untreated EFB fibre. The microfibrils of pre-treated fibre were separated from the initial connected structure and this exposed the cellulose to hydrolysis, thus increased the external surface area and the porosity of the pre-treated fibre (Xu et al., 2007). Generally, raw EFB fibre consists of 44.2% alpha cellulose, 33.5% hemicellulose and 20.4% lignin, respectively (Astima et al., 2002). After treating with alkali-microwave, cellulose composition increased to 64%, while hemicellulose and lignin composition reduced to 26% and 8%, respectively. Cellulose composition is also much higher in microwave treatment compared with conventional pre-treatment. Alkali-microwave pre-treated EFB fibre gave 30% soluble glucose higher than conventional pre-treatment when it was hydrolyzed with combination of cellulase and Novozyme 188. The optimum conditions obtained for hydrolysis process were at pH 5, 50 °C and 5:1 cellulase to Novozyme 188 ratio.