(671e) Intensification of Enzymatic Cellulose Hydrolysis Using High Frequency Ultrasound

Our research efforts involve the applications of ultrasonic and hydrodynamic cavitation to intensify and optimize the homogeneous and catalytic synthesis of biodiesel and the conversion of lignocellulosic biomass to ethanol and other chemicals for biofuels production so as to reduce cost and make the processes economically attractive for large-scale production. Lignocellulosic biomass contains about 50% cellulose, 25% hemicelluloses and 25% lignin. Conversion of biomass to ethanol consists of three basic steps: (1) pretreatment of biomass; (2) hydrolysis of cellulose; and (3) fermentation of glucose. The hydrolysis of cellulose can be carried out using dilute acids, concentrated acids or enzymes. Enzymatic hydrolysis is preferred over acid hydrolysis as it avoids the formation of fermentation inhibition products and does not require drastic operating conditions. However, enzymatic hydrolysis of cellulose is a very slow process requiring, in general, about 70-120 hrs to achieve appreciable conversions (~60-80%). Ultrasound is known to hasten both pretreatment and hydrolysis of biomass. An attempt has been made to reduce the time of enzymatic hydrolysis of cellulose using high frequency, low intensity ultrasound generated by novel multifrequency reactor. It was observed that the reducing sugar (glucose) yield obtained in the presence of ultrasound was twice as compared to in the absence of it. It was also found that the effect of ultrasound is only physical in nature and increased mass transfer due to increased surface area by cellulose fragmentation in the presence of ultrasound was responsible for the observed increase in the glucose yield. About 50% glucose yield was obtained in 24 hours in the presence of ultrasound using AVICEL microcrystalline cellulose and cellulase + cellobiase enzyme at 50°C and 5.2 pH.

References

(1) N.N. Mahamuni, Y.G. Adewuyi, "Optimization of the Synthesis of Biodiesel via Ultrasound-Enhanced Base-Catalyzed Transesterification of Soybean Oil Using a Multifrequency Ultrasonic Reactor". Energy & Fuels, 2009, 23, 2757 - 2766.

(2)N.N. Mahamuni, Y.G. Adewuyi, "Fourier Transform Infrared Spectroscopy (FTIR) Method to Monitor Soy Biodiesel and Soybean Oil in Transesterification Reactions, Petrodiesel-Biodiesel Blends, and Blend Adulteration with Soy Oil. Energy & Fuels. 2009, 23, 3773-3782.

(2) V.G. Deshmane, P.R. Gogate, A.B. Pandit. "Ultrasound-Assisted Synthesis of Biodiesel from Palm Fatty Acid Distillate" Ind. Eng. Chem. Res. 2009, 48, 7923 - 7927.