Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/27/2007
Publication Date: 5/19/2008
Citation: Yachmenev, V., Condon, B.D., Klasson, K.T., Lambert, A.H., Smith, J.N. 2008. Technical Aspects of Acceleration of Enzymatic Conversion of Corn Stover Biomass into Bio-fuels by Low Intensity, Uniform Ultrasound Field. 1st Annual World Congress of Industrial Biotechnology, Book of Abstracts. p. 50. Interpretive Summary:
Technical Abstract: One of the most critical stages of conversion of plant biomass into biofuels employs hydrolysis reactions between highly specific enzymes and matching substrates (e.g. corn stover cellulose with cellulase) that produce soluble sugars, which then could be converted into ethanol. Important benefits of enzymatic bio-conversion of plant cellulose include significant energy/water savings and low toxicity of resulting wastewater effluents, which are readily biodegradable. Despite these numerous advantages, a major limitation of enzymatic bio-processing is relatively slow reaction rates. Specifically, enzymatic conversion of plant biomass involves transfer of mass (enzyme macromolecules) from the processing liquid medium (enzyme solution) toward the surface of the solid substrate (plant biomass). Since this transfer of mass is controlled by diffusion, the overall reaction rate of enzymatic hydrolysis is governed by the diffusion rate of the enzyme macromolecules. In general, large three-dimensional enzyme macromolecules have very low diffusion rates, which greatly impede the overall rate of the hydrolytic reaction. Our research 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) the effect of cavitation is several hundred times greater in heterogeneous systems (solid-liquid) than in homogeneous, b) in water, maximum effects of cavitation occur at ~50 0C, which is the optimum temperature for many enzymes, c) cavitation effects caused by ultrasound greatly enhance the transport of enzyme macromolecules toward the substrate’s surface and, d) mechanical impacts, produced by collapse of cavitation bubbles, provide an important benefit of “opening up” the surface of substrates to the action of enzymes. It appears that the introduction of ultrasound energy during enzymatic bio-processing of corn stover biomass could significantly accelerate this process and make it more suitable for widespread industrial implementation.