Pretreatment of sugarcane bagasse with microwaves irradiation and its effects on the structure and on enzymatic hydrolysis

This paper refers to the new proposal of pre-treatment of sugarcane bagasse with microwave associated to glycerol, seeking greater release of fermentable sugars during enzymatic hydrolysis. The residue was subjected to microwave irradiation for 5 min with distilled water, phosphoric acid (pH 3.0) and glycerol (100%) before being enzymatically hydrolyzed using cellulase enzyme extract Myceliophthora thermophila M.7.7. and the commercial enzyme cocktail Celluclast 1.5 L. A variety of analyses including measurement of BET surface analysis, MET, TGA, DTG, DSC, ATR-FTIR and PAD-HPLC were used to facilitate the understanding of the physical and chemical characteristics of the solid fraction resulting from pre-treatment. Infrared spectra of untreated and treated bagasse in microwave irradiation and glycerol showed significant differences in the regions 1635, 1600 and 1510 related vibration of the aromatic ring, and the band at 1100 cm−1 is attributed to an overlap of C–O–H elongation of primary and secondary alcohols and at 980 cm−1 to stretching of glycosidic linkages C–O–C. The thermal analysis showed that the bagasse treated in a microwave irradiation and glycerol has higher thermal stability compared to the untreated bagasse. The experimental results indicated that 5.4 and 11.3% w/w of lignin and xylan fractions, respectively, are degraded after pretreatment of bagasse in microwave heating with glycerol. The highest yields of hydrolysis of hemicellulose (22.4%) and cellulose (40.2%) w/w were obtained in the reaction mixture containing the enzyme and Celluclast commercial cane bagasse treated in a microwave irradiation and glycerol after 24 h of incubation. The association of microwave and glycerol is a new alternative to deconstruction of lignocellulose structure.