Fermentation of rice hull by Aspergillus japonicus under ultrasonic pretreatment

The application of ultrasound for treating rice hull used as the fermentation substrate for xylooligosaccharides production was investigated. Aspergillus japonicus CY6-1 was selected to produce cellulolytic and xylanolytic enzymes from untreated rice hull (RH) and rice hull treated with ultrasound (USRH-M). The hemicellulose yield was increased to 1.4-fold with ultrasound, and treatment time was greatly shortened from 24 h to 1.5 h at 80 °C and 300 W/28 kHz. The morphology of RH from various pretreatments was observed with field emission scanning electron microscope (FESEM), revealing the surface structure of USRH-M smoother than that of RH. USRH-M was much easier to be utilized by fungi, to extend the stability of enzyme activity and to increase activities of CMCase, β-glucosidase, and xylanase compared with those of untreated RH. The final fermentative products were xylotetraose, xylohexaose, and higher molecular weight xylooligosaccharides, achieving xylohexaose yield for USRH-M 80% higher than that for RH group.

► Ultrasonic technology was applied to treat rice hull to product xylooligosaccharides.
► The best ultrasonic conditions were 300 W, 28 kHz, 80 °C, 250 mL vessel-type and 1.5 h.
► The treated time could be shorten, achieving 1.4-fold hemicellulose yield of RH.
► The fermentative products were xylooligosaccharides by Aspergillus japonicus CY6-1.
► Xylohexaose yield for USRHM achieved 80% higher than that for RH group.