Intensification of Biobased Processes
CHAPTER 8: Intensification of Enzymatic Hydrolysis of Cellulose Using High Frequency Ultrasound
Published:18 Jun 2018
In this work, intensification of the enzymatic hydrolysis of cellulose was investigated using a high multi-frequency ultrasonic reactor, and the effects of ultrasound on enzyme stability were addressed. The influence of ultrasound on glucose yields was evaluated using Avicel microcrystalline cellulose and cellulase + cellobiase enzymes at 50 °C and pH 5.2. The structure of the treated cellulose was studied using Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD). The overall effect of ultrasound was dependent upon parameters such as energy input, frequency, and irradiation duration. The best hydrolysis results occurred at 611 kHz and 104 W, with 50% and up to 70% glucose yield in 24 h and 40–50 h, respectively. The results indicated that the effect of ultrasound was mainly physical in nature. Ultrasound-induced cellulose fragmentation resulted in a surface area increase and crystallinity reduction, which increased mass transfer and, hence, the intensification of enzymatic hydrolysis leading to increased glucose yield. Overall, it appears that ultrasound and/or cavitation-assisted technologies are green techniques that have the potential to enhance hydrolysis of lignocellulosic materials for biofuel production and biorefinery applications; through physical and/or chemical mechanisms, and with little or no effect on the specific activity of the complex enzyme at typical treatment conditions.