Technical aspects of use of ultrasound nazakat2

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Technical aspects of use of ultrasound nazakat2

  1. 1. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro. M.E RESEARCH PROPOSAL USE OF ULTRASOUND FOR INTENSIFICATION OF ENZYMATIC BIO- PROCESSING. By Engineer; Nazakat Ali 07 TLE17 Supervised by: PROFESSOR; RAJA FAHAD ASHRAF DEPARTMENT OF TEXTILE ENGINEERING MUET, JAMSHORO. A research approach for the fulfillment of Masters of Textile Engineering Post Graduate Diploma leading to ME Textile Engineering
  2. 2. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro TITLE: OBJECTIVE: USE OF ULTRASOUND FOR INTENSIFICATION OF ENZYMATIC BIO-PROCESSING. BACKGROUND: Use of enzymatic processing in the food, textile, and bio-fuel applications is becoming increasingly popular, primarily because of rapid introduction of a new variety of highly efficient enzymes. In general, an enzymatic bio- processing generates less toxic and readily biodegradable wastewater effluents. The ever-increasing legislative pressures by governments worldwide to reduce the quantity/toxicity of industrial wastewaters will ensure even greater acceptance of enzymatic bio-processing in the future. 1. INTRODUCTION: Enzymatic processing of cotton textiles, like any wet processing system, involves transfer of mass (enzyme macromolecules) from the processing liquid medium (enzyme solution) across the surface of the textile substrate. Enzymatic reaction involves transport of the enzyme macromolecules and enzymatic reaction products to and from the fiber surface. Since both stages are 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 low diffusion rates and tend to react with outlaying cellulose fibers in cotton yarn, which could result in excessive fiber damage. Sonication of enzyme processing solution under specific conditions could provide a far more efficient transport mechanism for “bulky” enzyme macromolecules throughout the immediate border layer of liquid at the substrate surface. Generally, an application of ultrasound energy into the liquid medium has two primary effects: cavitation and heating. Sonication of liquid by low frequencies dissipates most of the ultrasound energy through cavitation phenomena, while sonication by high frequencies dissipates a Nazakat Ali Research Proposal 2010 Page 2 of 13
  3. 3. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro significant amount of energy through heating (at the expense of cavitational dissipation). In case of enzymatic bio-processing, the more important is cavitation - formation, growth, and implosive collapse of bubbles in a liquid. The dynamics of cavity growth and collapse are highly dependent on the type of liquid, presence of dissolved species and gases in the liquid, and temperature of the liquid. The imploding cavitation bubble causes the nearly adiabatic compression of the excess vapors inside of the cavity thus raising its pressures ~ 500 atm. and temperatures ~ 5, 500 oC (plasma conditions). The powerful ultrasonic irradiation of liquids produces a plethora of high energy chemical reactions. As the excess vapors in the cavitational bubble are compressed by the collapse, and its contents reach several thousand Kelvin, the trapped vapors are largely dissociated. For water, collapse of the cavitational bubble produces the high-energy intermediates such as H+ (atomic hydrogen), OH- (hydroxyl), e-(aq) (solvated electrons), H2O2 (hydrogen peroxide), HO2 (superoxide) and, H2 (molecular hydrogen). The formation of such highly reactive intermediates by collapsing cavitational bubbles should significantly affect the long term catalytic stability/activity of dissolved enzyme macromolecules. The common perception is that these highly reactive intermediates and powerful shock waves resulting from collapse of cavitation bubbles could severely damage or at least, inactivate the very sensitive and intricate structures of enzyme proteins. Unlike the cavitation bubbles collapse in homogenous systems (liquid-liquid interface), collapse of a cavitation bubbles in heterogeneous systems (e.g. enzyme solution – solid substrate) is different because cavitation bubbles that collapse on or near to a surface are non-symmetrical since the surface provides resistance to liquid flow. The result is an in-rush of liquid predominantly from the opposite side of the bubble (remote from the substrate surface) resulting in a powerful liquid jet (~450 m/sec) being formed and targeted at the surface. It is also important, that the rapid collapse of the cavitation bubbles generates significant shear forces in the bulk liquid Nazakat Ali Research Proposal 2010 Page 3 of 13
  4. 4. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro immediately surrounding the bubbles and, as a result, produces a strong stirring mechanical effect. These effects can significantly increase mass and heat transfer to the surface of the substrate by disrupting the interfacial boundary layers and also activate the catalytic performance of the enzyme macromolecules adsorbed onto the surface of substrate. It is well known that the diffusion transport of enzyme macromolecules toward the surface of a solid substrate could be enhanced to a certain degree by simple mechanical agitation of the processing solution, but it is also recognized that mechanical agitation is not a very effective stirring mechanism for the immediate border layer of liquid at a solid - liquid interface where the enzymatic reaction actually occurs. The first, immediate layer of liquid at solid - liquid interface is motionless, and then velocities of following layers quickly increase to the maximum constant value defined by the power of agitation of the bulk solution. Since the immediate adjusted layer of liquid at a solid – liquid interface is practically immobile the only available transport mechanism for enzyme macromolecules to reach substrate surface is diffusion. When microscopic cavitation bubbles collapse in the immediate vicinity of a substrate surface, they generate powerful shock waves that cause effective stirring/mixing of this adjusted layer of liquid. These shock waves generated by cavitation bubbles collapsing on and near the surface of substrate (e.g. cellulosic fibers) are an ideal stirring mechanism for the immediate layer of liquid at the solid-liquid interface where enzyme reactions take place. The forceful stirring/mixing of this normally immobile layer of liquid greatly improves the supply of enzyme macromolecules to the surface of a substrate. The following specific features of cavitation phenomena are very important for practical bio-processing application: a) Effect of cavitation is several hundred times greater in heterogeneous (e.g. all textile wet processes) than in homogeneous systems and Nazakat Ali Research Proposal 2010 Page 4 of 13
  5. 5. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro b) In water, maximum effects of cavitation occur at ~500 C, which is the nearly optimum temperature for many enzymatic bio-processing applications. However, when ultrasound specifically is used to inactivate enzymes and terminate enzymatic activity its actual efficiency is quite low. For example, the combined effects of heat, ultrasonic waves, and pressure may be used for inactivation of certain thermostable enzymes. The comprehensive overview of the combined effects of heat, pressure and ultrasound on microorganisms and enzymes enfold that the resistance of most microorganisms and enzymes to ultrasound is so high that the required intensity of ultrasound treatment would be impractical. Nazakat Ali Research Proposal 2010 Page 5 of 13
  6. 6. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 2. SCOPE OF PROJECT: In summary, we can formulate the necessary requirements to maximize the benefits of ultrasound energy for enzymatic bio-processing as follows: · Ultrasound Frequency: it appears that optimum sonication frequency should be in range of 20—100 kHz. These low sonication frequencies are more beneficial because: a) Most of the introduced ultrasound energy is dissipated through the cavitation mechanism rather than through heating. b) The lower sonication frequencies produce larger cavitation bubbles and therefore, more powerful “jets”, thus providing more vigorous stirring/mixing of the border layer of liquid at solid - liquid interface. c) Hardware for generation of low frequencies usually is more cost efficient. It is also important that in case of heterogeneous systems most of cavitation bubbles are generated close to the surface of the substrate thus providing an important additional benefit of the “opening up” of the surface of solid substrates as result of mechanical impacts produced by powerful “jets” of collapsing cavitational bubbles. Another imperative consideration is that, despite their close-packed and generally well-ordered structures, enzyme macromolecules are usually not entirely rigid and have some conformational flexibility in solution that helps them to properly position the “active” domain relative to the substrate. Therefore, vigorous stirring/agitation of the normally immobile border layer of liquid at the liquid-solid interface caused by sonication should help enzyme macromolecules more easily position themselves “fittingly” onto the substrate. And lastly, another valuable benefit of the intensive stirring/agitation of this border layer by collapsing cavitation bubbles is enhanced removal of the products of hydrolysis reaction from the reaction zone that should contribute to an overall increase in the reaction rate. Nazakat Ali Research Proposal 2010 Page 6 of 13
  7. 7. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 3. AIMS AND OBJECTIVES: Ultrasound Energy: it appears that optimum sonication power should be in range of 2-10 W/cm3. The low energy sonication of the enzyme solution improves the transport of enzyme macromolecules but does not generate an excessive amount of highly reactive intermediates. It is critically important to introduce ultrasound energy into the processing bath in the most uniform way. That criterion insures the uniform generation of cavitation bubbles throughout the bath and, as a result, uniform enhancement of transport of enzyme macromolecules toward substrate. On the whole, despite the apparent attractiveness of introduction of ultrasound energy for intensification of enzymatic bio-processing of natural fibers, it was unclear how ultrasound affects the complex structures of enzyme macromolecules and how significant the benefits of introduction of ultrasound energy could be. The objectives of our experiments were to study the influence of low level, uniform ultrasound field on the enzymatic bio-scouring and bio-finishing of cotton textiles. Nazakat Ali Research Proposal 2010 Page 7 of 13
  8. 8. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 4. APPLICATIONS OF THE PROJECT: Application of Ultrasound in Heterogeneous vs. Homogeneous Systems, since the effects of cavitation are several hundred items greater in heterogeneous than in homogeneous systems, it is appears that introduction of ultrasound could be economically justified only for solid-liquid systems. In homogeneous systems, the much less expensive mechanical agitation would probably suffice. It come into sight that sonication of the enzyme processing solution does not reduce the specific activity of enzyme macromolecules in any significant way, on a laboratory scale, introduction of ultrasonic energy in the reaction chamber during enzymatic bio-preparation/bio-finishing of cotton resulting in a significant improvement in enzyme efficiency. One possible explanation of the apparent inefficiency of ultrasound to inactivate enzyme macromolecules could be just their extremely low ratio to the huge quantity of solvent molecules (e.g. water) at the typically used enzyme processing concentrations of 4-5 g/liter. The combination of enzymatic bio-preparation/bio-finishing with sonication could significantly advance this new “green chemistry” process and made it more suitable for widespread industrial implementation, and this could greatly reduce the amount/toxicity of wastewater, energy consumption and processing costs. Further work can be made on different areas of textile wet processing such as bio-finishing, scouring, bleaching e.t.c. Nazakat Ali Research Proposal 2010 Page 8 of 13
  9. 9. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 5. DATA SOURCE AND RESEARCH METHODOLOGY. Materials: Desized, scoured, bleached, and mercerized clean cotton cloth will be used for all bio-finishing tests and original greige cotton cloth will be used in all bio-scouring tests. The weight loss and wettability for all samples treated under various conditions with enzyme and/or ultrasound will be determined and compared with samples of the original untreated cotton fabric. Ultrasonic Reactor: The enzymatic bio-processing of all textile samples shall be conducted in a parallel-plate Near-Field Acoustical Processor. This dual frequency ultrasonic reactor with thermal control capabilities will be equipped with two variable power generators that provided 0 – 3 W/cm2 of ultrasonic energy inside the reaction chamber. Pectinase bio-scouring of greige cotton: Raw unscoured (greige) cotton contains ~ 90% cellulose and various non-cellulosics such as waxes, pectins, proteins, fats, and coloring matter. To remove these hydrophobic non- cellulosics and produce a highly absorbent fiber that can be dyed and finished uniformly, the greige cotton is traditionally processed with boiling sodium hydroxide solution in the presence of wetting and sequestering agents. This industrial process requires large quantities of water and energy, and generates a highly alkaline wastewater effluent. It is suggested that alkaline pectinases might be a valuable alternative to harsh alkaline solutions in the preparation of cotton. The primary objective of test is to determine how enzymatic bio-scouring of cotton cloth with various concentrations of pectinase enzyme (0.1-1.0 g/L) are affected by sonication or not. A treatment time (30 min) will be selected primarily to emphasize the possible effect of sonication on the enzymatic bio- scouring rather than to achieve maximum absorbency of the sample. The average wettabilities of original samples and samples treated with various concentrations of BioPrep L pectinase with/without ultrasound will also be analyzed. Nazakat Ali Research Proposal 2010 Page 9 of 13
  10. 10. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro Experimental data: On the wettability of all treated samples will clearly show that the application of ultrasound energy during pectinase bio-scouring greatly improves and accelerate the process resulting in much shorter wicking time (200 vs. 600 sec). Interestingly, that maximum effect provided by sonication occurs at a concentration of 0.4 g/L, which is lower than recommended by the manufacturer (0.5 g/L). The overall uniformity of bio-preparation will substantially better in combined pectinase/ultrasound treatment than in pectinase only. Testing/Sampling: The primary objective of testing is to determine how enzymatic bio-finishing of cotton cloth with various concentrations of cellulase enzyme (1.0 - 8.0 g/L) would be affected by sonication. Triplicate samples of desized, scoured, bleached and mercerized cotton cloth (107 g/m2) will be treated with cellulase solution (Cellusoft L) TM in combination with/without sonication for 60 min (Liquor Ratio = 200:1). For all concentration ranges, the average weight loss of samples treated with a combination of ultrasound and Cellusoft L enzyme will be analyzed and compared with the samples of treated with enzyme. Nazakat Ali Research Proposal 2010 Page 10 of 13
  11. 11. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 5. Results and Discussions: Results: However, enzymatic bio-processing has several critical shortcomings that impede its wide acceptance by industries: expensive processing costs and slow reaction rates. Our research found that the introduction of a low energy, uniform ultrasound field into various 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 ~500C, which is the optimum temperature for many enzymes, c) Cavitation effects caused by ultrasound greatly enhance the transport of enzyme macromolecules toward substrate 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. Discussions: This study has potential for intensification of other technological processes that involve various types of specific enzymes and matching substrates. We can assume that practically any solid/liquid system that involves a reaction between enzyme macromolecules and solid substrate would greatly benefit from application of ultrasonic energy into the system. Nazakat Ali Research Proposal 2010 Page 11 of 13
  12. 12. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 6. Conclusions: A major incentive for embracing enzymatic bio-processing of natural fibers is that application of enzymes is much more environmentally benign and the reactions catalyzed are very specific and ensure more focused performance as a result. In contrast, traditional chemical processing is much less specific and often results in undesirable side effects, e.g. significant reduction in the degree of polymerization of cellulose. Enzymes used in cotton bio-processing act as catalysts to speed up complex chemical reactions such as the hydrolysis of cellulose (by cellulases) and pectins (by pectinases). Because they act as catalysts, relatively small amount of enzymes are required; if conditions are favorable to the specific enzyme, it will repeat the action (hydrolysis) many times during the process. Other potential benefits of enzymatic bio-processing include cost reduction through energy and water savings and better product quality. The comprehensive overview of the combined effects of heat, pressure and ultrasound on microorganisms and enzymes concluded that the resistance of most microorganisms and enzymes to ultrasound is so high that the required intensity of ultrasound treatment would be impractical. Nazakat Ali Research Proposal 2010 Page 12 of 13
  13. 13. Department of Textile Engineering Mehran University of Engineering & Technology, Jamshoro 7. REFERENCES: 1. W. Aehle: Enzymes in Industry, Wiley-VCH Verlag GmbH & Co. Weinheim, (2004) 219-231. 2. V. G. Yachmenev, E. J. Blanchard, A. H. Lambert: Use of ultrasonic energy for intensification of the bio-preparation of greige cotton. Ultrasonics, 42 (2004) 87-91. 3. F. J. Sala, J. Burgos, S. Condon, P. Lopes, L. Raso: Effect of heat and ultrasound on microorganizms and enzymes. New Methods of Food Preservation. (1995) 176-204. 4. I. Hua, R. H. Höchemer, M. R. Hoffmann: Sonochemical degradationof p- nitrophenol in parallel-plate near-field acoustical processor. Environmental Science & Technology, 29 (1995) 2790-2796. Nazakat Ali Research Proposal 2010 Page 13 of 13

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