Enzyme-free saccharification of cellulose to glucose using ultrasonic welding

Abstract

• Ultrasonic welding can decompose cellulose in a short time. • No enzymes or catalysts are required for cellulose degradation. • The present method can be applied to the process of producing bioethanol from nonedible biomass. Ultrasonic welding is a processing technology that can instantly fuse and join thermoplastic resins by applying minute amounts of ultrasonic vibration and pressure. The present study demonstrates that the frictional force or pressure caused by ultrasonic welding can cause cellulose decomposition without a saccharifying enzyme or catalysts. Ultrasonic waves of 19.5 kHz were irradiated downward on samples using a horn-type transducer. The cellulose specimens were composed of 15 – 105 stacked sheets of filter paper with high cellulose content, a sheet of cotton, and a sheet of hemp. The high frictional forces resulting from direct contact of cellulose with the ultrasonic horn tips decomposed the saccharides within a short time to produce glucose. Cellulose is decomposed into glucose through hydrolysis in an enzyme-free environment by ultrasonic irradiation, but then it is further decomposed into 5-hydroxymethylfurfural, furfural, and other compounds via a dehydration reaction caused by an increase in temperature of the reaction field from continuous ultrasonic irradiation. Glucose could be obtained from the cellulose without using an enzyme through ultrasonic welding. The result of decomposing cellulose, cotton, and hemp by this method revealed that a yield of 1.2% glucose could be obtained by decomposing filter paper.