Acceleration of the Enzymatic Hydrolysis of Corn Stover and Sugar Cane Bagasse Celluloses by Low Intensity Uniform Ultrasound

Authors: Yachmenev, Valeriy; Condon, Brian; Klasson, K Thomas; Lambert, Allan

Submitted to: Journal of Biobased Materials and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2009
Publication Date: 4/23/2009
Citation: Yachmenev, V., Condon, B.D., Klasson, K.T., Lambert, A.H. 2009. Acceleration of the Enzymatic Hydrolysis of Corn Stover and Sugar Cane Bagasse Celluloses by Low Intensity Uniform Ultrasound. Journal of Biobased Materials and Bioenergy. 3(1):25-31.

Interpretive Summary: The cost-competitive production of bio-ethanol and other biofuels is currently impeded, mostly by high cost and low efficiency of enzymatic hydrolysis of feedstock biomass and especially plant celluloses. Despite substantial reduction in the cost of production of cellulolytic enzymes in recent times, the actual conversion of plant cellulose into sugars still remains an expensive and slow step. Our research has found that the introduction of a low energy, uniform ultrasound field into enzyme processing solutions greatly improved their effectiveness by significantly increasing their reaction rate. On a laboratory scale, introduction of low level, uniform ultrasonic energy in the reaction chamber during enzymatic hydrolysis of ground corn stover and sugar cane bagasse samples resulted in a significant improvement in enzyme efficiency. The combined enzyme/sonication hydrolysis of corn stover and sugar cane bagasse plant celluloses could significantly accelerate this critical step in the overall conversion of this agricultural waste biomass into biofuels. On the whole, this research demonstrated that under specific conditions, carefully controlled introduction of ultrasound energy during enzymatic bio-processing has a very good potential for intensification of variety of technological processes that involve many types of industrial enzymes and matching substrates. Groups benefiting from this development include the textile, food, cosmetic, pharmaceutical and many others industries.

Technical Abstract: The cost-competitive production of bio-ethanol and other biofuels is currently impeded, mostly by high cost and low efficiency of enzymatic hydrolysis of feedstock biomass and especially plant celluloses. Despite substantial reduction in the cost of production of cellulolytic enzymes in recent times, the actual conversion of plant cellulose into sugars still remains an expensive and slow step. Our research has found that the introduction of a low energy, uniform ultrasound field into enzyme processing solutions greatly improved their effectiveness by significantly increasing their reaction rate. It has been established that the following specific features of combined enzyme/ultrasound bio-processing are critically important: a) cavitation effects caused by introduction of ultrasound field into the enzyme processing solution greatly enhance the transport of enzyme macromolecules toward the substrate’s surface, b) the effect of cavitation is several hundred times greater in heterogeneous systems (solid-liquid) than in homogeneous, c) mechanical impacts, produced by the collapse of cavitation bubbles, provide an important benefit of “opening up” the surface of solid substrates to the action of enzymes and d) in water, the maximum effects of cavitation occur at ~50 C, which is the optimum temperature for many enzymes. On a laboratory scale, introduction of low level, uniform ultrasonic energy in the reaction chamber during enzymatic hydrolysis of corn stover and sugar cane bagasse cellulose samples resulted in a significant improvement in enzyme efficiency. The combined enzyme/sonication hydrolysis of corn stover, bagasse and similar plant celluloses could significantly accelerate this critical step in the overall conversion of agricultural waste biomass into biofuels.