XYLANASES: MOLECULAR PROPERTIES AND APPLICATIONS
5. APPLICATIONS OF XYLANASES
Microbial hemicellulases, especially xylanases, have important applications in industry due to their enormous potential to modify and transform the lignocellulose and cell wall materials abundant in vegetal biomass which is used in a wide variety of industrial processes. The biotechnological application of xylanases began in the 1980s in the preparation of animal feed, and later expanded to the food, textile and paper industries. Since then the biotechnological use of these enzymes has increased dramatically, covering a wide range of industrial sectors. At present, xylanases together with cellulases and pectinases account for 20% of the global industrial enzyme market (Polizeliet al., 2005).
Xylan is present in large amounts in wastes from the agricultural and food indus-tries. Xylanases are thus of increasing importance for the bioconversion of ligno-cellulosic biomass, including urban solid residues, to xylose and other fermentable sugars for the production of biological fuels (ethanol) (Lee, 1997). Bioconversion of xylan to the low calorie sweetener xylitol is a promising field where xylanases can also play a key role (Polizeliet al., 2005). Other less well documented potential applications of xylanases include their use as additives in detergents, in the prepa-ration of plant protoplasts, the production of pharmacologically active oligosaccha-rides as antioxidants, and the use of xylanases possessing transxylosidase activity for the synthesis of new surfactants (Bhat, 2000; Collinset al., 2005).
Xylanases are used as additives in animal feeds for monogastric animals, together with cellulases, pectinases and many other depolymerizing enzymes. Enzyme degra-dation of arabinoxylans, commonly found as ingredients of feeds, reduces the viscosity of the raw materials thus facilitating better mobility and absorption of other components of the feed and improving nutritional value (Polizeliet al., 2005).
The incorporation of xylanase into the rye- or wheat-based diets of broiler chickens resulted in an improvement in weight gain of chicks and their feed conversion efficiency (Bedford and Classen, 1992). Similar improvements can be obtained for pigs fed on a wheat-based diet supplemented with xylanases and phospholipases (Dieboldet al., 2005).
The application of xylanases along with pectinases in the juice and wine industries facilitates the extraction and clarification of the final products (Bhat, 2000). These enzymes can also increase the stability of fruit pulp and release aroma precursors. As regards the latter, a recombinant yeast strain expressing a fungal xylanase produced a wine with increased fruity aroma (Gangaet al., 1999). Xylanases can be also used in brewing to reduce beer’s haze and viscosity, and to increase wort filterability (Polizeliet al., 2005). As baking additives, xylanases degrade flour hemicelluloses resulting in a redistribution of water from pentosans to gluten, thus giving rise to an increase in bread volume and crumb quality, and an antistaling effect (Linko et al., 1997). This can be further enhanced when amylases are used in combination with xylanases (Monfortet al., 1996).
The major current industrial application of xylanases is in the pulp and paper industry where xylanase pretreatment facilitates chemical bleaching of pulps, resulting in important economic and environmental advantages over the non-enzymatic process (Viikari et al., 1994; Bajpai, 2004). Xylanases do not remove lignin-based chromophores directly but instead degrade the xylan network that traps the residual lignin. Degradation of xylan in xylan-lignin complexes or reprecipi-tated on the surface of fibres after kraft cooking, allows a more efficient extraction of lignin by the bleaching chemicals. Microscopic analysis of pulps shows that xylanase treatment opens up fibre surface which exhibits detached material, in contrast to the smooth surface of untreated fibres (Fig. 3) (Roncero et al., 2000).
Xylanase-boosted bleaching results in up to 20–25% savings on chlorine-based chemicals and a reduction of 15–20% in the generation of pollutant organic chlorine compounds from lignin degradation (adsorbable organic halogens, AOX)
(A)
(B)
(C)
(D)
(Viikari et al., 1994; Bajpai, 2004). The reduction in the amount of chemical bleaching agents required to obtain a target paper brightness has contributed to the replacement of elemental chlorine by the less polluting chlorine dioxide in elemental chlorine free (ECF) bleaching sequences, or to the total replacement of chlorine compounds by alternative bleaching agents such as hydrogen peroxide and ozone in total chlorine free (TCF) bleaching sequences.
The bleaching efficiency of different fungal and bacterial xylanases has been analysed. Although many of the enzymes tested are highly efficient as bleaching aids, notable differences can appear depending on the family and traits of each particular enzyme (Elegiret al., 1995; Clarkeet al., 1997). The response to enzyme-aided bleaching can also be affected by the bleaching sequence, wood species concerned and the pulping method (Suurnäkki et al., 1996; Nelson et al., 1995;
Christov et al., 2000). At present, many microbial xylanases are available on the market and are successfully used in pulp mills (Beget al., 2001).
In relation to the bleaching process, xylanase treatment can modify pulp-refining properties. In some cases, enzymatically treated pulps require greater beating, while the strength properties of the paper are not affected or only slightly modified (Ronceroet al., 2003; Vicuñaet al., 1995). A decrease in xylan content by enzyme treatment has been reported to modify the ageing and brightness reversion of pulps and paper, which can show increased stability and less yellowing tendency after enzyme treatment (Buchertet al., 1997).
Besides xylanases, other hemicellulases have also been tested as bleaching aids with various results. Among them, -mannanases have been shown to facilitate bleaching, eliminating residual lignin and increasing paper brightness, though the effect of mannanases is usually less pronounced than that of xylanases (Montiel et al., 1999; Bhat, 2000). Advances in understanding lignin degradation has resulted in the proposal of a different strategy for bleaching, involving the direct removal of lignin by lignin depolymerizing enzymes (laccases and peroxidases). Laccases from several fungi and fromStreptomyceshave been successfully assayed (Bourbonnais et al., 1997; Sigoillot et al., 2005; Arias et al., 2003) whereas few examples of brightness improvement with manganese peroxidases have been reported to date.
The application of xylanases in the pulp and paper industry is not restricted to bleaching. The good results obtained in this field have stimulated the evaluation of the use of xylanases in other stages of pulp and paper manufacture. Application of xylanases in mechanical pulping, pulp drainage or the deinking of recycled fibres is currently being evaluated, and the promising results obtained are leading to an expanding use of xylanases in this industry and an increasing importance for xylanases in the world enzyme market.
Figure 3.SEM analysis of cellulose fibres. Scanning electron micrographs of fully unbleached(A)and (C), or oxygen delignified(B)and(D)Eucalyptuskraft pulps before or after xylanase treatment.(A) and (B) untreated pulps showing fibres with smooth surfaces;(C) and (D)xylanase treated pulps showing flakes and filaments of material detached from the fibre surface. Courtesy of Dr. T. Vidal (Ronceroet al., 2000)
REFERENCES
Ali, M.K., Kimura, T., Sakka, K. and Ohmiya, K. (2001) The multidomain xylanase Xyn10B as a cellulose-binding protein inClostridium stercorarium. FEMS Microbiol. Lett.198, 79–83.
Arias, M.E., Arenas, M., Rodríguez, J., Soliveri, J., Ball, A.S. and Hernández, M. (2003) Kraft pulp biobleaching and mediated oxidation of a nonphenolic substrate by laccase fromStreptomyces cyaneus CECT 3335. Appl. Environ. Microbiol.69, 1953–1958.
Bajpai, P. (2004) Biological bleaching of chemical pulps. Crit. Rev. Biotechnol.24, 1–58.
Bayer, E.A., Belaich, J.P., Shoham, Y. and Lamed, R. (2004) The cellulosomes: multienzyme machines for degradation of plant cell wall polysaccharides. Annu. Rev. Microbiol.58, 521–554.
Bedford, M.R. and Classen, H.L. (1992) The influence of dietary xylanase on intestinal viscosity and molecular weight distribution of carbohydrates in rye-fed broiler chicks. In: Visser, J., Beldman, G., Kusters-van Someren, M.A., Voragen, A.G.J. (eds) Xylans and xylanases. Elsevier, Amsterdam, pp.
361–370.
Beg, Q.K., Kapoor, M., Mahajan, L. and Hoondal, G.S. (2001) Microbial xylanases and their industrial applications: a review. Appl. Microbiol. Biotechnol.56, 326–338.
Bhat, M.K. (2000) Cellulases and related enzymes in biotechnology. Biotechnol. Adv.18, 355–383.
Biely, P. (1985) Microbial xylanolytic systems. Trends Biotechnol.3, 286–290.
Biely, P., Vršanská, M., Tenkanen, M. and Kluepfel, D. (1997) Endo--1,4-xylanase families: differences in catalytic properties. J. Biotechnol.57, 151–166.
Black, G.W., Hazlewood, G.P., Millward-Sadler, S.J., Laurie, J.I. and Gilbert, H.J. (1995) A modular xylanase containing a novel non-catalytic xylan-specific binding domain. Biochem. J.307, 191–195.
Blanco, A., Díaz, P., Zueco, J., Parascandola, P. and Pastor, F.I.J. (1999) A multidomain xylanase from aBacillussp. with a region homologous to thermostabilizing domains of thermophilic enzymes.
Microbiology145, 2163–2170.
Boraston, A.B., Bolam, D.N., Gilbert, H.J. and Davies, G.J. (2004) Carbohydrate-binding modules:
fine-tuning polysaccharide recognition. Biochem. J.382, 769–781.
Borneman, W.S., Ljungdahl, L.G., Hartley, R.D. and Akin, D.E. (1993) Feruloyl andp-coumaroyl esterases from the anaerobic fungusNeocallimastixstrain MC-2: properties and functions in plant cell wall degradation. In: Coughlan M.P and Hazlewood G.P (eds) Hemicelluloses and hemicellulases.
Portland Press, London and Chapel Hill, pp. 85–102.
Bourbonnais, R., Paice, M.G., Freiermuth, B., Bodie, E. and Borneman, S. (1997) Reactivities of various mediators and laccases with kraft pulp and lignin model compounds. Appl. Environ. Microbiol.63, 4627–4632.
Buchert, J., Bergnor, E., Lindblad, G., Viikari, L. and Ek, M. (1997) Significance of xylan and gluco-mannan in the brightness reversion of kraft pulps. Tappi J. 80(6):165–171.
Clarke, J.H., Rixon, J.E., Ciruela, A., Gilbert, H.J. and Hazlewood, G.P. (1997) Family-10 and family-11 xylanases differ in their capacity to enhance the bleachability of hardwood and softwood paper pulps.
Appl. Microbiol. Biotechnol.48, 177–183.
Collins, T., Gerday, C. and Feller, G. (2005) Xylanases, xylanase families and extremophilic xylanases.
FEMS Microbiol. Rev.29, 3–23.
Coughlan, M.P. and Hazlewood, G.P. (1993)-1,4-D-Xylan-degrading enzyme systems: biochemistry, molecular biology and applications. Biotechnol. Appl. Biochem.17, 259–289.
Coughlan, M.P., Tuohy, M.G., Filho, E.X.F., Puls, J., Claeyssens, M., Vrsanská, M. and Hughes, M.M.
(1993) Enzymological aspects of microbial hemicellulases with emphasis on fungal systems. In:
Coughlan M.P and Hazlewood G.P (eds) Hemicelluloses and hemicellulases. Portland Press, London and Chapel Hill, pp. 53–84.
Coutinho, P.M. and Henrissat, B. (1999) Carbohydrate-active enzymes: an integrated database approach.
In: Gilbert, H.J., Davies, G.S., Henrissat, B., Svensson. B. (eds) Recent Advances in Carbohydrate Bioengineering. The Royal Society of Chemistry, Cambridge, pp. 3–12.
Christov, L., Biely, P., Kalogeris, E., Christakopoulos, P., Prior, B.A. and Bhat, M.K. (2000) Effects of purified endo--1,4-xylanases of family 10 and 11 and acetyl xylan esterases on eucalypt sulfite dissolving pulp. J. Biotechnol.83, 231–244.
Diebold, G., Mosenthin, R., Sauer, W.C., Dugan, M.E.R. and Lien, K.A. (2005) Supplementation of xylanase and phospholipase to wheat-based diets for weaner pigs. J. Anim. Physiol. Anim. Nutr.89, 316–325.
De Vries, R.P., Kester, H.C.M., Poulsen, C.H., Benen, J.A.E. and Visser, J. (2000) Synergy between enzymes fromAspergillusinvolved in the degradation of plant cell wall polysaccharides. Carbohydr.
Res.327, 401–410.
De Vries, R.P. and Visser, J. (2001)Aspergillus enzymes involved in degradation of plant cell wall polysaccharides. Microbiol. Mol. Biol. Rev.65, 497–522.
Elegir, G., Sykes, M. and Jeffries, T.W. (1995) Differential and synergistic action ofStreptomyces endoxylanases in prebleaching of kraft pulps. Enzyme Microb. Technol.17, 954–959.
Emami, K., Nagy, T., Fontes, C.M.G.A., Ferreira, L.M.A. and Gilbert, H.J. (2002) Evidence for temporal regulation of the twoPseudomonas cellulosaxylanases belonging to glycoside hydrolase family 11.
J. Bacteriol.184, 4124–4133.
Fontes, C.M.G.A., Gilbert, H.J., Hazlewood, G.P., Clarke, J.H., Prates, J.A.M., McKie, V.A., Nagy, T., Fernandes, T.H. and Ferreira, L.M.A. (2000) A novel Cellvibrio mixtus family 10 xylanase that is both intracellular and expressed under non-inducing conditions. Microbiology146, 1959–1967.
Fujimoto, Z., Kuno, A., Kaneko, S., Yoshida, S., Kobayashi, H., Kusakabe, I. and Mizuno, H. (2000) Crystal structure ofStreptomyces olivaceoviridisE-86 beta-xylanase containing xylan-binding domain.
J. Mol. Biol.300, 575–585.
Gallardo, O., Diaz, P. and Pastor, F.I.J. (2003) Characterization of a Paenibacillus cell-associated xylanase with high activity on aryl-xylosides: a new subclass of family 10 xylanases. Appl. Microbiol.
Biotechnol.61, 226–233.
Ganga, M.A., Piñaga, F., Vallés, S., Ramón, D. and Querol, A. (1999) Aroma improving in microvini-fication processes by the use of a recombinant wine yeast strain expressing theAspergillus nidulans xlnA gene. Int. J. Food Microbiol.47, 171–178.
Gilbert, H.J. and Hazlewood, G.P. (1993) Bacterial cellulases and xylanases. J. Gen. Microbiol.139, 187–194.
Gilkes, N.R., Henrissat, B., Kilburn, D.G., Miller Jr., R.C. and Warren, R.A.J. (1991) Domains in microbial ß-1,4-glycanases: sequence conservation, function, and enzyme families. Microbiol. Rev.
55, 303–315.
Henrissat, B. (1991) A classification of glycosyl hydrolases based on amino acid sequence similarities.
Biochem. J.280, 309–316.
Henrissat, B. and Bairoch, A. (1996) Updating the sequence-based classification of glycosyl hydrolases.
Biochem. J.316, 695–696.
Honda, Y. and Kitaoka, M. (2004) A family 8 glycoside hydrolase fromBacillus haloduransC-125 (BH2105) is a reducing end xylose-releasing exo-oligoxylanase. J. Biol. Chem. 279, 55097:55103.
Irwin, D., Jung, E.D. and Wilson, D.B. (1994) Characterization and sequence of aThermomonospora fuscaxylanase. Appl. Environ. Microbiol.60, 763–770.
Jiang, Z.Q., Deng, W., Li, X.T., Ai, Z.L., Li, L.T. and Kusakabe, I. (2005) Characterization of a novel, ultra-large xylanolytic complex (xylanosome) fromStreptomyces olivaceoviridisE-86. Enzyme Microb. Technol.36, 923–929.
Jun, H.S., Ha, J.K., Malburg Jr., L.M., Gibbins, A.M.V. and Forsberg, C.W. (2003) Characteristics of a cluster of xylanase genes inFibrobacter succinogenesS85. Can. J. Microbiol.49, 171–180.
Kataeva, I.A., Seidel III, R.D., Shah, A., West, L.T., Li, X.L. and Ljungdahl, L.G. (2002) The fibronectin type 3-like repeat from theClostridium thermocellumcellobiohydrolase CbhA promotes hydrolysis of cellulose by modifying its surface. Appl. Environ. Microbiol.68, 4292–4300.
Krause, D. O., Denman, S.E., Mackie, R.I., Morrison, M., Rae, A.L., Attwood, G.T. and McSweeney, C.S. (2003) Opportunities to improve fiber degradation in the rumen: microbiology, ecology, and genomics. FEMS Microbiol. Rev.27, 663–693.
Kolenová, K., Vršanská. M. and Biely, P. (2005) Purification and characterization of two minor endo--1,4-xylanases ofSchizophyllum commune. Enzyme. Microb. Technol.36, 903–910.
Kubata, B.K., Takamizawa, K., Kawai, K., Suzuki, T. and Horitsu, H. (1995) Xylanase IV, an exoxy-lanase ofAeromonas caviaeME-1 which produces xylotetraose as the only low-molecular-weight oligosaccharide from xylan. Appl. Environ. Microbiol.61, 1666–1668.
Kulkarni, N., Shendye, A. and Rao, M. (1999) Molecular and biotechnological aspects of xylanases.
FEMS Microbiol. Rev.23, 411–456.
Larson, S.B., Day, J., Barba de la Rosa, A.P., Keen, N.T. and McPherson, A. (2003) First crystallographic structure of a xylanase from glycoside hydrolase family 5: Implications for catalysis. Biochemistry 42, 8411:8422.
Lee, J. (1997) Biological conversion of lignocellulosic biomass to ethanol. J. Biotechnol.56, 1–24.
Lee, Y.E., Lowe, S.E., Henrissat, B. and Zeikus, J.G. (1993) Characterization of the active site and thermostability regions of endoxylanase fromThermoanaerobacterium saccharolyticumB6A-RI. J.
Bacteriol.175, 5890–5898.
Linder, M. and Teeri, T.T. (1997) The roles and function of cellulose-binding domains. J. Biotechnol.
57, 15–28.
Linko, Y.Y., Javanainen, P. and Linko, S. (1997) Biotechnology of bread baking. Trends Food Sci.
Technol.8, 339–344.
Lo Leggio, L., Jenkins, J., Harris, G.W., Pickersgill, R.W. (2000) X-ray crystallographic study of xylopentaose binding toPseudomonas fluorescensxylanase A. Proteins41, 362–373.
Lynd, L.R., Weimer, P.J., van Zyl, W.H. and Pretorius, I.S. (2002) Microbial cellulose utilization:
fundamentals and biotechnology. Microbiol. Mol. Biol. Rev.66, 506–577.
Matte, A. and Forsberg, C.W. (1992) Purification, characterization, and mode of action of endoxylanases 1 and 2 fromFibrobacter succinogenesS85. Appl. Environ. Microbiol.58, 157–168.
Monfort, A., Blasco, A., Prieto, J.A. and Sanz, P. (1996) Combined expression ofAspergillus nidulans endoxylanase X24 andAspergillus oryzae-amylase in industrial bakers’s yeasts and their use in bread making. Appl. Environ. Microbiol.62, 3712–3715.
Montiel, M.D., Rodríguez, J., Pérez-Leblic, M.I., Hernández, M., Arias, M.E. and Copa-Patiño, J.L.
(1999) Screeening of mannanase in actinomycetes and their potential application in the biobleaching of pine kraft pulps. Appl. Microbiol. Biotechnol.52, 240–245.
Nelson, S.L., Wong, K.K.Y., Saddler, J.N. and Beatson, R.P. (1995) The use of xylanase for peroxide bleaching of kraft pulps derived from different softwood species. Pulp Paper Can. 96 (7):42–45.
Pell, G., Szabo, L., Charnock, S.J., Xie, H., Gloster, T.M., Davies, G.J. and Gilbert, H.J. (2004a) Struc-tural and biochemical analysis ofCellvibrio japonicusxylanase 10C. J. Biol. Chem.279, 11777–11788.
Pell, G., Taylor, E.J., Gloster, T.M., Turkenburg, J.P., Fontes, C.M.G.A., Ferreira, L. M. A., Nagy, T., Clark, S. J., Davies, G.J. and Gilbert, H. J. (2004b) The mechanisms by which family 10 glycoside hydrolases bind decorated substrates. J. Biol. Chem.279, 9597–9605.
Polizeli, M.L.T.M., Rizzatti, A.C.S., Monti, R., Terenzi, H.F., Jorge, J.A. and Amorim, D.S. (2005) Xylanases from fungi: properties and industrial applications. Appl. Microbiol. Biotechnol. 67, 577–591.
Puls, J. (1992)-glucuronidases in the hydrolysis of wood xylans. In: Visser, J., Beldman, G., Kusters-van Someren, M.A., Voragen, A.G.J. (eds) Xylans and xylanases. Elsevier, Amsterdam, pp. 213–224.
Roncero, M.B., Torres, A.L., Colom, J.F. and Vidal, T. (2000) Effects of xylanase treatment on fibre morphology in totally chlorine free bleaching (TCF) ofEucalyptuspulp. Process Biochem.36, 45–50.
Roncero, M.B., Torres, A.L., Colom, J.F. and Vidal, T. (2003) Effect of xylanase on ozone bleaching kinetics and properties ofEucalyptuskraft pulp. J. Chem. Technol. Biotechnol.78, 1023–1031 Ruiz-Arribas, A., Fernández-Abalos, J.M., Sánchez, P., Garda, A.L. and Santamaría, R.I. (1995)
Overpro-duction, purification, and biochemical characterization of a xylanase (Xys1) from Streptomyces halstediiJM8. Appl. Environ. Microbiol.61, 2414–2419.
Rye, C.S. and Whithers, S.G. (2000) Glycosidase mechanisms. Curr. Opin. Chem. Biol.4, 573–580.
Sabini, E., Wilson, K.S., Danielsen, S., Schulein, M. and Davies, G.J. (2001) Oligosaccharide binding to family 11 xylanases: both covalent intermediate and mutant product complexes display (25)B conformations at the active centre. Acta Crystallogr. D57:1344–1347.
Saha, B.C. (2000)-l-arabinofuranosidases: biochemistry, molecular biology and application in biotech-nology. Biotechnol. Adv.18, 403–423.
Shallom, D. and Shoham, Y (2003) Microbial hemicellulases. Curr. Op. Microbiol.6, 219–228.
Sigoillot, C., Camarero, S., Vidal, T., Record, E., Asther, M., Pérez-Boada, M., Martínez, M.J., Sigoillot, J.C., Asther, M., Colom, J.F. and Martínez, A.T. (20005) Comparison of different fungal enzymes for bleaching high-quality paper pulps. J. Biotechnol.115, 333–343.
Sunna, A. and Antranikian, G. (1997) Xylanolytic enzymes from fungi and bacteria. Crit. Rev.
Biotechnol.17, 39–67.
Sunna, A., Gibbs, M.D. and Bergquist, P.L. (2000) The thermostabilizing domain, XynA, ofCaldibacillus cellulovoransxylanase is a xylan binding domain. Biochem. J.346, 583–586.
Suurnäkki, A., Clark, T.A., Allison, R.W., Viikari, L. and Buchert, J. (1996) Xylanase- and mannanase-aided ECF and TCF bleaching. Tappi. J. 79(7):111–117.
Tomme, P., Boraston, A., McLean, B., Kormos, J., Creagh, A.L., Sturch, K., Gilkes, N.R., Haynes, C.A., Warren, R.A.J. and Kilburn, D.G. (1998) Characterization and affinity applications of cellulose-binding domains. J. Chromatogr. B715, 283–296.
Van Petegem, F., Collins, T., Meuwis, M.A., Gerday, C., Feller, G. and van Beeumen, J. (2003) The structure of a cold-adapted family 8 xylanase at 1.3 Å resolution. J. Biol. Chem.278, 7531–7539.
Vardakou, M., Flint, J., Christakopoulos, P., Lewis, R.J., Gilbert, H.J. and Murray, J.W. (2005) A family 10Thermoascus aurantiacusxylanase utilizes arabinose decorations of xylan as significant substrate specificity determinants. J. Mol. Biol.352, 1060–1067.
Vicuña, R., Oyarzún, E. and Osses, M. (1995) Assessment of various commercial enzymes in the bleaching of radiata pine kraft pulps. J. Biotechnol.40, 163–168.
Viikari, L., Kantelinen, A., Sundquist, J. and Linko, M. (1994) Xylanases in bleaching: from an idea to the industry. FEMS Microbiol. Rev.13, 335–350.
Williamson, G., Kroon, P.A. and Faulds, C.B. (1998) Hairy plant polysaccharides: a close shave with microbial esterases. Microbiology.144, 2011–2023.
Wong, K.K.Y., Tan, L.U.L. and Saddler, J.N. (1988) Multiplicity of-1,4-xylanase in micro-organisms:
functions and applications. Microbiol. Rev.52, 305–317.