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Enzymes: A revaluation in textile processing by Muhammad Ayaz Shaikh, Assistant Professor, College of Textile Engineering, SFDAC. Abstract The use of enzymes in the textile chemical processing is rapidly gaining globally recognition because of their non-toxic and eco-friendly characteristics with the increasingly important requirements for textile manufacturers to reduce pollution in textile production. Enzymes sources, activity, specificity, reaction, mechanism and thermodynamics, function of t
     D  y   e   i  n   g   P  r   i  n   t   i  n   g   F   i  n   i   s   h   i  n   g 48  PTJ April 2010 Abstract The use of enzymes in the textile chemical processing is rap-idly gaining globally recognition because of their non-toxic andeco-friendly characteristics with the increasingly importantrequirements for textile manufacturers to reduce pollution in tex-tile production. Enzymes sources, activity, specificity, reaction,mechanism and thermodynamics, function of textile processingwith enzymes, major enzymatic applications in textile wet pro-cessing and promising areas of enzyme applications in textile pro-cessing are discussed. The aim is to provide the textiletechnologist with an understanding of enzymes and their usewith textile materials. Enzymes are proteins Enzymes are generally globular proteins and like other pro-teins consist of long linear chains of amino acids that fold to pro-duce a three-dimensional product. Each unique amino acidsequence produces a specific structure, which has unique proper-ties. Individual protein chains may sometimes group together toform a protein complex. Biocatalyst Enzymes are biocatalysts, and by their mere presence, andwithout being consumed in the process, enzymes can speed upchemical processes that would otherwise run very slowly. After the reaction is complete, the enzyme is released again, ready tostart another reaction. Most of the biocatalyst have limited stabil-ity and over a period of time they lose their activity and are notstable again. Usually most enzymes are used only once and dis-carded after their catalytic action. Nomenclature The International Union of Biochemistry and Molecular Biology have developed a nomenclature for enzymes, the ECnumbers where each enzyme is described by a sequence of four numbers preceded by EC . The first number broadly classifiesthe enzyme based on its mechanism.The top-level classification isEC 1 Oxidoreductases: catalyze oxidation/reduction reactions.EC 2 Transferases: transfer a functional group.EC 3 Hydrolases: catalyze the hydrolysis of various bonds.EC 4 Lyases: cleave various bonds by means other than hydrolysisand oxidation.EC 5 Isomerases: catalyze isomerization changes within a singlemolecule.EC 6 Ligases: join two molecules with covalent bonds.At present, more than 2,000 enzymes have been isolated andcharacterized. Among them about 50 microbial enzymes haveindustrial applications.There is a large number of microorganisms which produce avariety of enzymes. Microorganisms producing enzymes of textileimportant are listed Table 1. Activity The activities of enzymes are determined by their three-dimen-sional structure. Most enzymes can be denatured, which disrupt thethree-dimensional structure of the protein. Denaturation may bereversible or irreversible depending on the enzyme.There are two proposed models of enzyme substrate complexformation. 1. Lock-and-key Model or Template In 1894 Emil Fischer provided the lock-and-key model assum-ing that the active site is a perfect fit for a specific substrate andthat once the substrate binds to the enzyme no further modifica-tion is necessary. It is a simplistic model. 2. Induced fit Model or Koshland Model In 1958 Daniel Koshland suggested a modification to the lockand key model. Instead of flexible structures, the active site iscontinually reshaped by interactions with the substrate as thesubstrate interacts with the enzyme. As a result, the substratedoes not simply bind to a rigid active site; the amino acid sidechains which make up the active site are molded into the precisepositions that enable the enzyme to perform its catalytic function.In some cases, such as glycosidases, the substrate molecule alsochanges shape slightly as it enters the active site. The active sitecontinues to change until the substrate is completely bound, atwhich point the final shape and charge is determined. The prod-uct is usually unstable in the active site due to steric hindrancesthat force it to be released and return the enzyme to its initialunbound state. Enzymes: A revaluation in textile processing by Muhammad Ayaz Shaikh, Assistant Professor, College of Textile Engineering, SFDAC. Table-1 Micro organismsEnzymes1. Bacteria Bacillus subtilisAmylaseB. coagulans α amylaseB.licheniformis α amylase, protease 2. Fungi A. nigerAmylases, protease, pectinase, glucose oxidaseA. oryzaeAmylases, lipase, proteaseCandela lipolyticaLipaseP. notatumGlucose oxidaseRhizopus spLipaseTrichoderma reeseiCellulaseT. virideCellulaseAscomycetes α amylaseBasidiomycetes α - amylaseAspergillus spPectinase¸ lipase Induced fit model Substrate enteringactive site ofenzyme.Enzyme/sub-strate complexEnzyme/productscomplexProducts leavingactive site ofenzymeProductsEnzyme changes shapeslightly as substrate bindsSubstrateActive site  D  y ei  n  gP r i  n t  i  n  gF i  ni   s h i  n  g PTJ April 2010 49  Enzymatic reactions Victor Henri elaborated enzyme reactions in two stages. In thefirst, the substrate binds reversibly to the enzyme, forming theenzyme-substrate complex. This is sometimes called the Michaeliscomplex. The enzyme then catalyzes the chemical step in thereaction and releases the product. Mechanisms Enzymes can act in several ways, all of which lower   ∆  G‡:  Lowering the activation energy by creating an environmentin which the transition state is stabilized.  Lowering the energy of the transition state, but without dis-torting the substrate, by creating an environment with theopposite charge distribution to that of the transition state.  Providing an alternative pathway. For example, temporarilyreacting with the substrate to form an intermediate ES com-plex, this is not possible without enzyme.  Reducing the reaction by bringing substrates together in thecorrect orientation to react.  Reactions speed up with increase in temperatures. However,the enzyme’s shape deteriorates on overheating and onlywhen the temperature comes back to normal does theenzyme regain its shape. Some enzymes like thermolabileenzymes work best at low temperatures.Enzymes like all catalysts do not alter the position of the chemicalequilibrium of the reaction. They do not alter the equilibrium itself, butonly the speed at which it is reached. Usually, in the presence of anenzyme, the reaction runs in the same direction as it would without theenzyme, just more quickly. However, in the absence of the enzyme,other possible uncatalyzed, spontaneous reactions might lead to differ-ent products, because in those conditions this different product isformed faster. Enzymes in textile Today enzymes have become an integral part of the textile pro-cessing. There are two well-established enzyme applications in the tex-tile industry. Firstly, in the preparatory finishing area amylases arecommonly used for  desizing process and secondly, in the finishingarea cellulases are used for  softening, bio-stoning and reducing ofpilling propensity for cotton goods.However, there is little known about potential enzyme usage inother textile areas. At present, applications of pectinases, lipases, pro-teases, catalases, xylanases etc., are used in textile processing. Thereare various applications which entail enzymes included fading ofdenim and non-denim, bio-scouring, bio-polishing, wool finishing,peroxide removal, decolourization of dyestuff, etc. Now the use ofbiocatalyst has become state of the art in the textile industry. Researchand development in this sector is primarily concentrating on:  Optimizing and making routine the use of technical enzymes inprocesses that are already established in the textile industry today.  Replacing established conventional processes with the aid of newtypes of enzymes, particularly from extremophile micro-organ-isms, under stringent conditions.  Preparing enzyme-compatible dyestuff formulations, textile aux-iliary agents and chemical mixtures.  Producing new or improved textile product properties by enzy-matic treatment.  Providing biotechnological dyes and textile auxiliary agents, whichare suitable for industrial use, and can possibly be synthesized in-situ.Most of the textile enzymes are those that catalyze the diges-tion or hydrolysis of certain large organic molecules like starch,cellulose, and protein. The enzymes actually attack these complexmolecules, accelerating their digestion and yielding simpler sub-stances. Since this process of digestion is referred to as hydrolysis,the enzymes that catalyze the process are considered to behydrolyzing enzymes or hydrolases. The hydrolyzing enzymes include: 1.Amylases, which catalyze the digestion of starch into small seg-ments of multiple sugars and into individual soluble sugars.2.Proteases or proteinase, which split up proteins into their compo-nent amino acid building blocks.3.Lipases, which split up animal and vegetable fats and oils into their component part glycerol and fatty acids.4.Cellulases (of various types) which break down the complex mol-ecule of cellulose into more digestible components of single andmultiple sugars.5.Beta-glucanase or gumase, which digests one type of vegetablegum into sugars and / or dextrins.6.Pectinase which digests pectin and similar carbohydrates of plantsrcin. Amylase All amylases are glycoside hydrolases and act on α -1, 4-glycosidicbonds that hydrolyse starch down into sugar. Amylase is present inhuman saliva; the pancreas also makes amylase. Plants and some bac-teria also produce amylase.Specific amylase proteins are designated by different Greek letters.The α -amylases (EC are calcium metalloenzymes, completelyunable to function in the absence of calcium. By acting at randomlocations along the starch chain, α -amylase breaks down long-chaincarbohydrates, ultimately yielding maltotriose and maltose from amy-lose, or maltose, glucose and limit dextrin from amylopectin. α -amy-lase tends to be faster-acting than β -amylase as it can act anywhere onthe substrate. β -amylase (EC is also synthesized by bactetria, fungi, andplants. Working from the non-reducing end, β -amylase catalyzes thehydrolysis of the second α -1, 4 glycosidic bond, cleaving off two glu-cose units (maltose) at a time.In addition to cleaving the last α -1, 4 glycosidic linkages at thenonreducing end of amylose and amylopectin, yielding glucose, γ -amylase (EC cleaves α -1, 6 glycosidic linkages. Unlike theother forms of amylase, γ -amylase is most efficient in acidic environ-ments and has an optimum pH of 3.Starch is used as a sizing agent in textile comprising of linear chained amylose and branched chain amylopectin. The desizingprocess was carried out by treating the fabric with chemicals such asacids, alkali or oxidising agents. Enzyme + SubstrateK1K2K3K4Active ComplexEnzyme + Products Thermodynamics     D  y   e   i  n   g   P  r   i  n   t   i  n   g   F   i  n   i   s   h   i  n   g 50  PTJ April 2010 The amylose is bioconverted to 100% by the alpha- amylaseinto glucose whereas the amylopectin is converted to 50% into glu-cose and maltose. Bio desizing is preferred due to their high effi-ciency and specific action. Amylases bring about complete removalof the size without any harmful effects on the fabric besides ecofriendly behavior. Pectinase Pectinase (EC is a general term for enzymes such aspectolyase, pectozyme and polygalacturonase. Pectinases hydrolysepectin, a polysaccharide substrate that is found in the cell walls ofplants into galacturonic acid and small sugars. Commercially avail-able pectinases contain only very little cellulases and fiber damageshould be limited as cellulose itself is not targeted.Pectinases are reported from various microbial sources. Fungalpectinases have been extracted from Aspergillus niger, Penicilliumfrequentans, Sclerotium rolfsii, and Rhizoctonia solani. However these enzymes are optimally active in acidic conditions. Alkalineactive pectinases have been obtained from Penicilium italicum andAspergillus sp. Pectinases have an optimum temperature and pH atwhich they are most active. For example, a commercial pectinasemight typically be activated at 45 to 55 °C and work well at pH of4.5 to 5.5. If pectinase is boiled it is denatured making it harder toconnect with the pectin at the active site.Today, highly alkaline chemicals caustic soda is used for scouring.These chemicals not only remove the non-cellulosic impurities fromthe cotton, but also attack the cellulose leading to heavy strength lossand weight loss in the fabric. Furthermore, using these hazardouschemicals result in high COD, BOD and TDS in the waste water.Recently a new enzymatic scouring process known as 'Bio-Scouring' is used in textile wet-processing with which all non-cellu-losic components from native cotton are removed. After thisBio-Scouring process, the cotton has an intact cellulose structure,with lower weight loss and strength loss. The fabric gives better wetting and penetration properties, making subsequent bleachprocess easy and resultantly giving much better dye uptake. It alsoreduces environmental burden by reducing waste water treatment.Enzymatic scouring process can be applied to cellulosic fibresand their blends (for both woven and knitted goods) in continuousand discontinuous processes. When enzymatic desizing is applied, itcan be combined with enzymatic scouring. The process can beapplied using jet, overflow, winch, pad-batch, pad-steam and pad-roll equipment. Catalase Catalase (EC is a tetramer of four polypeptide chains,each over 500 amino acids long. It contains four porphyrin hemegroups that allow the enzyme to react with the hydrogen peroxide.Catalase has one of the highest turnover numbers of all enzymes;one molecule of catalase can convert millions of molecules of hydro-gen peroxide to water and oxygen per second. The optimum pH for human catalase is approximately 7, and has a fairly broad maximum(the rate of reaction does not change appreciably at pH between6.8 and 7.5). The pH optimum for other catalases varies between 4and 11 depending on the species. The optimum temperature alsovaries by species. Catalase is a common enzyme found in nearly allliving organisms. Catalase is also universal among plants, and manyfungi are also high producers of the enzyme.Natural fabrics such as cotton are normally bleached withhydrogen peroxide before dyeing. Catalase enzyme is used to breakdown hydrogen peroxide bleaching liquor into water molecules andless reactive gaseous oxygen.2 H 2 O 2 → 2 H 2 O + O 2 Compared with the traditional clean¬up methods, the enzy-matic process results in cleaner waste water or reduced water con-sumption, a reduction of energy and time. Reuse of the bleachingliquor after hydrogen peroxide bleaching is already possible todayby using the enzyme catalase after bleaching. This enzyme destroysexcess hydrogen peroxide, making use of the bleaching liquor for other finishing stages possible. Cellulase Cellulase, 1, 4-(1,3;1,4)- β -D-Glucan-4-glucanohydrolase (EC3.2.1.4) is a linear polysaccharide of glucose residues connected by β -1,4 linkages. Cellulase refers to a class of enzymes although cellu-lases are distributed throughout the biosphere; they are most man-ifest in fungi and microbial sources. Cellulases are produced chieflyby fungi, bacteria, and protozoans that catalyze the cellulolysis ofcellulose. However, there are also cellulases produced by other typesof organisms such as plants and animals. There are several differentkinds of cellulases which differ structurally and mechanistically.Trichoderma reesei secrets cellulase in high amount, therefore thisfungus is used for commercial production of cellulase.There are three types of reaction catalyzed by cellulases:1.Breakage of the non-covalent interactions present in the crys-talline structure of cellulose (endo-cellulase).2.Hydrolysis of the individual cellulose fibers to break it intosmaller sugars (exocellulase).3. Hydrolysis of disaccharides and tetrasaccharides into glucose(beta-glucosidase).The commercially available cellulases are a mixture of enzymesviz., Endogluconases, Exogluconases and Cellobiases.Endogluconases are subclass of cellulase enzymes which randomlyattack the cellulose and hydrolyze the 1-4 glucosidic linkage of cel-lobiose chain. Exoglucanases of cello-biohydrolases are again sub-class of cellulose enzyme which hydrolyses 1-4 glucosidic linkageof cellulose to release cellotiose from the cellulose chain andCellobiases are enzymes which hydrolyse cellobiose into soluble glu-cose units. All these three enzymes act synergistically on cellulose tohydrolyse them. Protease A protease enzyme breaks down proteins. It conducts proteoly-sis, that is, begins protein catabolism by hydrolysis of the peptidebonds that link amino acids together in the polypeptide chain form-ing the protein. Proteases work best in acidic conditions. Proteases,also known as proteinases or proteolytic enzymes occur naturally inall organisms and belong to hydrolase class of enzymes, classifiedbased on the source from which it is extracted, optimum tempera-ture of activity. Proteases precisely act on peptide bonds formed byspecific amino acids to hydrolyze them.Commercial proteases are available, which can work in differentrange of pH and temperature. Trypsin (pancreatic), Papain basedand alkaline proteases find industrial applications in textiles. Themodified proteolytic enzyme enables the reaction of the enzymewith wool to be controlled, so that less degradation of the wooloccurs than in similar treatments with the native protease. An anti-felting effect has been achieved without any significant weight lossbeing caused by the modified protease during the treatment. Thisnovel enzymatic process leads to environmentally friendly produc-tion of machine washable wool.Proteases are the most widely used enzymes in the detergentindustry. They remove protein stains such as grass, blood, egg andhuman sweat. These organic stains have a tendency to adherestrongly to textile fibres. Proteases hydrolyse proteins and breakthem down into more soluble polypeptides or free amino acids. As  D  y ei  n  gP r i  n t  i  n  gF i  ni   s h i  n  g PTJ April 2010 51  a result of the combined effect of surfactants and enzymes, stub-born stains can be removed from fibres. Laccase Laccases (EC are copper-containing oxidase enzymesthat are found in many plants, fungi, and microorganisms. The useof lignin degrading white-rot fungi has attracted increasing scientificattention as these organisms are able to degrade a wide range ofrecalcitrant organic compounds such as polycyclic aromatic hydro-carbons, chlorophenol, and various azo, heterocyclic and polymericdyes. The major enzymes associated with the lignin degradation arelaccase, lignin peroxidase, and manganese peroxidase. Theseenzymes can be used for textile dyeing/finishing, and many other industrial, environmental uses.In textile dyeing large amounts of dyestuffs are used. The dis-charge effluent has high COD, BOD, suspended solids and intensecolour due to the extensive use of dyes. This type of water must betreated before discharging it into the environment. It was found thatthe fungi Trametes Modesta laccase showed the highest potential totransform the textile dyes into colourless products. The rate of thelaccase catalyzed decolourization of the dyes increases with theincrease in temperature up to certain degree above which the dyedecolourization decreases or does not take place at all. The optimumpH for laccase catalyzed decolourization depends on the type of thedye used. Textile dyestuffs with different structures are decolourizedat different rates.Another study carried out by E. Abadulla et al, has shown thatthe enzymes Pleurotus ostreatus, Schizophyllum Commune,Sclerodium Rolfsii, Trametes Villosa, and Myceliophtora Thermiphiliaefficiently decolourized a variety of structurally different dyes. Thisstudy also shows that the rate of reaction depends on the structureof the dye and the enzyme. Lipase A lipase (EC is a water-soluble enzyme, a subclass of theesterases that catalyzes the hydrolysis of ester bonds in water–insol-uble, lipid substrates. It is primarily produced in the pancreas but isalso produced in the mouth and stomach. Most people produce suf-ficient amounts of pancreatic lipase. Lipases from fungi and bacteriaserve important roles in human practices as ancient as yogurt andcheese fermentation. However, lipases are also being exploited ascheap and versatile catalysts to degrade lipids in more modern appli-cations.Though enzymes can easily digest protein stains, oily and fattystains have always been troublesome to remove. The trend towardslower washing temperatures has made the removal of grease spotsan even bigger problem. This applies particularly to materials madeup of a blend of cotton and polyester. The lipase is capable ofremoving fatty stains such as fats, butter, salad oil, sauces and thetough stains on collars and cuffs. Glucose oxidase The glucose oxidase enzyme (GOx) (EC is a dimericprotein. It is naturally found in honey. Commercially, it is oftenextracted from Aspergillus niger.At university of Auburn (USA) glucose oxidase was used for bleaching. The result showed whiteness index 15-20 degreeimprovement with low strength loss. Conventional preparation ofcotton requires high amounts of alkaline chemicals and conse-quently, huge quantities of rinse water are generated.An alternative to this process is to use a combination of suitableenzyme systems. Amyloglucosidases, Pectinases, and glucose oxi-dases are selected that are compatible concerning their active pHand temperature range. A combination of two or all three prepara-tion steps with minimal amounts of treatment baths and rinse water showed compatible results in Whiteness, absorbency, dyeability andtensile properties of the treated fabrics. Xylanase In past years, interest in xylanases was concentrated particularlyon enzymatic paper bleaching. In textile industry xylanases candestroy the coloured attendant substances of cotton. The quantityof chemicals required in peroxide bleaching could be reduced by thistype of enzymatic bleaching.According to a research “Enzymes for Removal of Non-Cellulosic By-Products of Bast Fibers” the removal of noncellulosiccompounds, such as lignin and hemicelluloses, was approachedusing xylanases in blends with cellulases. For hemp and linen goodsvery promising results were obtained especially when mechanicalaction was involved. However, Jute fibers with the highest lignincontent of all bast fibers showed a short-lived bleaching effect whenthese enzymes were used.At the Hamburg-Harburg (D) University of Technology, a com-prehensive screening programmed for isolating exremophile micro-organisms (like starch, proteins, and hemicellulose for example) hasbeen implemented which is able to produce enzymes for breakingdown biopolymers, alkanes, polyaromatic carbohydrates plus fatsand oils. Within the framework of these studies, a range of biotech-nologically relevant enzymes like amylases, xylanases, proteases,lipases and DNA polymerases for example have been enriched andcharacterized. Conclusion The use of various enzymes is in the early stages of develop-ment but their innovative applications are increasing and spreadingrapidly into all areas of textile processing. Enzyme producing com-panies constantly improve their products for more flexible applica-tion conditions and a more wide-spread use. The textile industry cangreatly benefit from the expanded use of these enzymes as non-toxic, environmentally friendly compounds if their effects on thetextile substrate and the basic mechanisms involved are better understood. References 1.Boyer, P.D. “The enzymes” 3rd ed. Vol. 5. Academic Press, Inc., New York.2.Fersht, Alan. “Enzyme structure and mechasnism”. San Francisco: W.H. BrendaThe comprehensive enzyme information system. Retrived 4 April 2007.3.Briggs G.E., Haldane J.B.S. “A note on the kinetics of enzyme action”.Biochem. J. 19 (2): PMID 16743508.4.R.C.Duby. “A text book of Biotechnology”. S. Chand & Company press. 2005.ISBN: 81-219-0916-3.5.Chelikani P, Fita I, Loewen PC. “Diversity of structures and properties amongcatalases”. Cell. Mol. Life Sci. 61 (2): 192–208. January 2004.6.Svendsen A. “Lipase protein engineering”. Biochim Biophys Acta 1543 (2):PMID 11150608, 2000.7.Barrett A.J., Rawlings ND, Woessner JF. “The handbook of proteolyticenzymes”. Academic Press, 2003. ISBN 0-12-079610-4.8.M. M. Shrivastava & Rashmi sanghi “Chemistry Of green environment”.Narosa publishing house. 2005. ISBN: 81-9319-620-6.9.Tony Godfrey & Stuart west. “Industrial Enzymology”, 2nd ed.10.Navnath D. Pingale “Eco-friendly textiles through application of bio-technol-ogy” Cavaco-Paulo, G Gubitz, Graz “Textile processing with enzymes”.Woodhead Publishing Limited. August 2003. ISBN-13: 978 1 85573 610 8.12.Kh. M. Gaffar Hossain, Maria Diaz Gonzalez, Guillem Rocasalbas Lozano andTzanko, “Multifunctional modification of wool using an enzymatic process inaqueous- organic media”. Journal of biotechnology Volume 141, Issue 1-2,April 2009. 
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