Hemicellulases: their occurrence, purification, properties, and mode of action

Gene cloning, DNA sequencing, and expression of thermostable beta-mannanase from Bacillus stearothermophilus

A DNA genomic library constructed from Bacillus stearothermophilus, a gram-positive, facultative thermophilic aerobe that secretes a thermostable beta-mannanase, was screened for mannan hydrolytic activity. Recombinant beta-mannanase activity was detected on the basis of the clearing of halos around Escherichia coli colonies grown on a dye-labelled substrate, Remazol brilliant blue-locust bean gum. The nucleotide sequence of the mannanase gene, manF, corresponded to an open reading frame of 2,085 bp that codes for a 32-amino-acid signal peptide and a mature protein with a molecular mass of 76,089 Da. From sequence analysis, ManF belongs to glycosyl hydrolase family 5 and exhibits higher similarity to eukaryotic than to bacterial mannanases. The manF coding sequence was subcloned into the pH6EX3 expression plasmid and expressed in E. coli as a recombinant fusion protein containing a hexahistidine N-terminal sequence. The fusion protein has thermostability similar to the native enzyme and was purified by Ni2+ affinity chromatography. The values for the kinetic parameters Vmax and Km were 384 U/mg and 2.4 mg/ml, respectively, for the recombinant mannanase and were comparable to those of the native enzyme.

Structure and function analysis of Pseudomonas plant cell wall hydrolases

Hydrolysis of the major structural polysaccharides of plant cell walls by the aerobic soil bacterium Pseudomonas fluorescens subsp. cellulosa is attributable to the production of multiple extracellular cellulase and hemicellulase enzymes, which are the products of distinct genes belonging to multigene families. Cloning and sequencing of individual genes, coupled with gene sectioning and functional analysis of the encoded proteins have provided a detailed picture of structure/function relationships and have established the cellulase-hemicellulase system of P. fluorescens subsp. cellulosa as a model for the plant cell wall degrading enzyme systems of aerobic cellulolytic bacteria. Cellulose- and xylan-degrading enzymes produced by the pseudomonad are typically modular in structure and contain catalytic and noncatalytic domains joined together by serine-rich linker sequences. The cellulases include a cellodextrinase; a beta-glucan glucohydrolase and multiple endoglucanases, containing catalytic domains belonging to glycosyl hydrolase families 5, 9, and 45; and cellulose-binding domains of families II and X, both of which are present in each enzyme. Endo-acting xylanases, with catalytic domains belonging to families 10 and 11, and accessory xylan-degrading enzymes produced by P. fluorescens subsp. cellulosa contain cellulose-binding domains of families II, X, and XI, which act by promoting close contact between the catalytic domain of the enzyme and its target substrate. A domain homologous with NodB from rhizobia, present in one xylanase, functions as a deacetylase. Mananase, arabinanase, and galactanase produced by the pseudomonad are single domain enzymes. Crystallographic studies, coupled with detailed kinetic analysis of mutant forms of the enzyme in which key residues have been altered by site-directed mutagenesis, have shown that xylanase A (family 10) has 8-fold alpha/beta barrel architecture, an extended substrate-binding cleft containing at least six xylose-binding pockets and a calcium-binding site that protects the enzyme from thermal inactivation, thermal unfolding, and attack by proteinases. Kinetic studies of mutant and wild-type forms of a mannanase and a galactanase from P. fluorescens subsp. cellulosa have enabled the catalytic mechanisms and key catalytic residues of these enzymes to be identified.

Softwood hemicellulose-degrading enzymes from Aspergillus niger: purification and properties of a beta-mannanase

The enzymes needed for galactomannan hydrolysis, i.e., beta-mannanase, alpha-galactosidase and beta-mannosidase, were produced by the filamentous fungus Aspergillus niger. The beta-mannanase was purified to electrophoretic homogeneity in three steps using ammonium sulfate precipitation, anion-exchange chromatography and gel filtration. The purified enzyme had an isoelectric point of 3.7 and a molecular mass of 40 kDa. Ivory nut mannan was degraded mainly to mannobiose and mannotriose when incubated with the beta-mannanase. Analysis by 1H NMR spectroscopy during hydrolysis of mannopentaose showed that the enzyme acts by the retaining mechanism. The N-terminus of the purified A. niger beta-mannanase was sequenced by Edman degradation, and comparison with Aspergillus aculeatus beta-mannanase indicated high identity. The enzyme most probably lacks a cellulose binding domain since it was unable to adsorb on cellulose.

Scan-rate dependence in protein calorimetry: the reversible transitions of Bacillus circulans xylanase and a disulfide-bridge mutant

The stabilities of Bacillus circulans xylanase and a disulfide-bridge-containing mutant (S100C/N148C) were investigated by differential scanning calorimetry (DSC) and thermal inactivation kinetics. The thermal denaturation of both proteins was found to be irreversible, and the apparent transition temperatures showed a considerable dependence upon scanning rate. In the presence of low (nondenaturing) concentrations of urea, calorimetric transitions were observed for both proteins in the second heating cycle, indicating reversible denaturation occurs under those conditions. However, even for these reversible processes, the DSC curves for the wild-type protein showed a scan-rate dependence that was similar to that in the absence of urea. Calorimetric thermograms for the disulfide mutant were significantly less scan-rate dependent in the presence of urea than in the urea-free buffer. The present data show that, just as for irreversible transitions, the apparent transition temperature for the reversible denaturation of proteins can be scan-rate dependent, confirming the prediction of Lepock et al. (Lepock JR, Rithcie KP, Kolios MC, Rodahl AM, Heinz KA, Kruuf J, 1992, Biochemistry 31:12706-12712). The kinetic factors responsible for scan-rate dependence may lead to significant distortions and asymmetry of endotherms, especially at higher scanning rates. This points to the need to check for scan-rate dependence, even in the case of reversible denaturation, before any attempt is made to analyze asymmetric DSC curves by standard thermodynamic procedures. Experiments with the disulfide-bridge-containing mutant indicate that the introduction of the disulfide bond provides additional stabilization of xylanase by changing the rate-limiting step on the thermal denaturation pathway.

Purification and properties of ArfI, an alpha-L-arabinofuranosidase from Cytophaga xylanolytica

An alpha-L-arabinofuranosidase (alpha-L-arabinofuranoside arabinofuranohydrolase [EC 3.2.1.55]; referred to below as ArfI) from Cytophaga xylanolytica XM3 was purified 85-fold by anion-exchange and hydrophobic interaction column chromatography. The native enzyme had a pI of 6.1 and an apparent molecular mass of 160 to 210 kDa, and it appeared to be a trimer or tetramer consisting of 56-kDa subunits. With p-nitrophenyl-alpha-L-arabinofuranoside as the substrate, the enzyme exhibited a K(m) of 0.504 mM and a Vmax of 319 mumol.min-1.mg of protein-1, and it had optimum activity at pH 5.8 and 45 degrees C. ArfI was relatively stable over a pH range of 4 to 10 and at temperatures up to 45 degrees C, and it retained nearly full activity when stored at 4 degrees C for periods as long as 24 months. The enzyme also released arabinose from 4-methylumbelliferyl-alpha-L-arabinofuranoside, as well as from rye, wheat, corn cob, and oat spelt arabinoxylans and sugar beet arabinan, but not from arabinogalactan. ArfI showed no hydrolytic activity toward a range of p-nitrophenyl- or 4-methylumbelliferyl-glycosides other than arabinoside, for which it was entirely specific for the alpha-L-furanoside configuration. ArfI interacted synergistically with three partially purified endoxylanase fractions from C. xylanolytica in hydrolyzing rye arabinoxylan. However, cell fractionation studies revealed that ArfI was largely, if not entirely, cytoplasmic, so its activity in vivo is probably most relevant to hydrolysis of arabinose-containing oligosaccharides small enough to pass through the cytoplasmic membrane. Antibodies prepared against purified ArfI also cross-reacted with arabinofuranosidases from other freshwater and marine strains of C. xylanolytica, as well as with some proteins that did not possess arabinofuranosidase activity. To our knowledge, this is the first alpha-L-arabinofuranosidase to be purified and characterized from any gliding bacterium.

Endo-beta-1,4-xylanase families: differences in catalytic properties

Microbial endo-beta-1,4-xylanases (EXs, EC 3.2.1.8) belonging to glycanase families 10 (formerly F) and 11 (formerly G) differ in their action on 4-O-methyl-D-glucurono-D-xylan and rhodymenan, a beta-1,3-beta-1,4-xylan. Two high molecular mass EXs (family 10), the Cryptococcus albidus EX and XlnA of Streptomyces lividans, liberate from glucuronoxylan aldotetrauronic acid as the shortest acidic fragment, and from rhodymenan an isomeric xylotriose of the structure Xyl beta 1-3Xyl beta 1-4Xyl as the shortest fragment containing a beta-1,3-linkage. Low molecular mass EXs (family 11), such as the Trichoderma reesei enzymes and XlnB and XlnC of S. lividans, liberate from glucuronoxylan an aldopentauronic acid as the shortest fragment, and from rhodymenan an isomeric xylotetraose as the shortest fragment containing a beta-1,3-linkage. The structure of the oligosaccharides was established by: NMR spectroscopy, mass spectrometry of per-O-methylated compounds and enzymic hydrolysis by beta-xylosidase and EX, followed by analysis of products by chromatography. The structures of the fragments define in the polysaccharides the linkages attacked and non-attacked by the enzymes. EXs of family 10 require a lower number of unsubstituted consecutive beta-1,4-xylopyranosyl units in the main chain and a lower number of consecutive beta-1,4-xylopyranosyl linkages in rhodymenan than EXs of family 11. These results, together with a greater catalytic versatility of EXs of family 10, suggest that EXs of family 10 have substrate binding sites smaller than those of EXs of family 11. This suggestion is in agreement with the finding that EXs of family 10 show higher affinity for shorter linear beta-1,4-xylooligosaccharides than EXs of family 11. The results are discussed with relevant literature data to understand better the structure-function relationship in this group of glycanases.

Action patterns and mapping of the substrate-binding regions of endo-(1-->5)-alpha-L-arabinanases from Aspergillus niger and Aspergillus aculeatus

The substrate binding sites of endo-(1-->5)-alpha-L-arabinanases (EC 3.2.1.99) from Aspergillus niger and Aspergillus aculeatus were investigated using reduced and regular (1-->5)-alpha-L-arabino-oligosaccharides and high performance anion exchange chromatographic analysis. Calculation of bond cleavage frequencies and kcat/K(m) parameters for these substrates enabled the determination of the number of arabinofuranosyl binding subsites and the estimation of the binding affinities of each subsite. The A. aculeatus endo-arabinanase has six subsites arranged symmetrically around the catalytic site, while the A. niger endo-arabinanase has five subsites; two from the catalytic site towards the non-reducing end of the bound substrate and three toward the reducing end. The two subsites directly adjacent to the catalytic sites in both the A. niger and A. aculeatus endo-arabinanase have near-zero net free energy of binding. These results are unlike most glycopyranosyl endo-hydrolases studied which have net negative (unfavourable) energies of interaction at these two subsites, and may be related to the greater conformational flexibility of arabinofuranosyl residues than glycopyranosyl residues. The complete subsite maps are also rationalized with regard to the observed action patterns of these enzymes on linear (1-->5)-alpha-L-arabinan.

Screening of fungal beta-xylanases for production of acidic xylooligosaccharides using in situ reduced 4-O-methylglucuronoxylan as substrate

Fungal beta xylanases were screened for production of acidic xylooligomers from 4-O-methylglucuronoxylan. In situ reduced hardwood xylan was used as substrate because the products of neutral- and acidic-branched xylooligomers help define substrate specificity of the enzymes. Borohydride reduction in situ transformed 30% of 4-O-methyl-alpha-D-glucopyranosyluronic acid residues into 4-O-methyl-alpha-D-glucopyranosyl residues and reduced C-1 end groups in the xylan backbones. A total of ten beta-xylanase fractions from four fungi were partially purified by chromatography by anion exchange and molecular sieving, and graded qualitatively for enzymatic hydrolysis of the substrate. The yield of acidic xylooligomers was highly affected by whether alpha-glucuronidases were present in the beta-xylanase fractions. Some fractions gave free 4-O-methyl-alpha-D-glucopyranosyluronic acid, but none of the enzyme fractions could release free 4-O-methyl-alpha-D-glucose. Among the beta-xylanase fractions studied, xylanase II of Trichoderma viride was the best producer of aldotetraouronic acid [2-O-(4-O-methyl-alpha-D-glucopyranosyluronic acid)-D-xylotriose]. The results obtained suggested that there was a difference in the steric hindrance of the branch point on fungal beta-xylanases between 4-O-methyl-alpha-D-glucopyranosyl and 4-O-alpha-D-glucopyranosyluronic acid residues.

Xylanolytic enzymes from fungi and bacteria

The development of new analytical techniques and the commercial availability of new substrates have led to the purification and characterization of a large number of xylan-degrading enzymes. Furthermore, the introduction of recombinant DNA technology has resulted in the selection of xylanolytic enzymes that are more suitable for industrial applications. For a successful integration of xylanases in industrial processes, a detailed understanding of the mechanism of enzyme action is, however, required. This review gives an overview of various xylanolytic enzyme systems from bacteria and fungi that have been described recently in more detail.

Microorganisms and enzymes involved in the degradation of plant fiber cell walls

One of natures most important biological processes is the degradation of lignocellulosic materials to carbon dioxide, water and humic substances. This implies possibilities to use biotechnology in the pulp and paper industry and consequently, the use of microorganisms and their enzymes to replace or supplement chemical methods is gaining interest. This chapter describes the structure of wood and the main wood components, cellulose, hemicelluloses and lignins. The enzyme and enzyme mechanisms used by fungi and bacteria to modify and degrade these components are described in detail. Techniques for how to assay for these enzyme activities are also described. The possibilities for biotechnology in the pulp and paper industry and other fiber utilizing industries based on these enzymes are discussed.

Hemicellulose-degrading bacteria and yeasts from the termite gut

Termites play a major role in the recycling of photosynthetically fixed carbon. With the aid of their symbiotic intestinal flora, they are able to degrade extensively wood constituents such as cellulose and hemicellulose. Nevertheless, the microbial species involved in the degradation of hemicelluloses are poorly defined. The purpose of this paper was to examine the microflora involved in hemicellulose degradation. Different aerobic and facultatively anaerobic bacteria and yeasts were isolated using xylan, arabinogalactan and carboxymethylcellulose as substrates. Gram-positive isolates belonged to the genera Bacillus, Paenibacillus, Streptomyces or the actinobacteria group, while the Gram-negative strains were assigned to the genera Pseudomonas, Acinetobacter, Ochrobactrum, and to genera belonging to the family Enterobacteriaceae. The spectrum and activity of xylan- and arabinogalactan-hydrolysing glycosidases of these new isolates, together with additional bacterial strains originally obtained from enrichments with aromatic compounds were determined.

Production of extracellular beta-mannanases by yeasts and yeast-like microorganisms

A new screening method for simultaneous detection of endo-beta-1,4-mannanase and endo-beta-1,4-xylanase producing microorganisms is described. Two differently dyed substrates Ostazin Brilliant Red-galactomannan and Remazol Brilliant Blue-xylan were incorporated into the same agar media. Decolorizing of one or both substrates around the cell colonies indicates secretion of the corresponding enzyme(s). The method was used to screen 449 yeasts and yeast-like microorganisms belonging to 68 different genera. The secretion of endo-beta-1,4-mannanases and/or endo-beta-1,4-xylanases was found within 10 genera (42 positive strains out of 261 tested). A low frequency of occurrence of endo-beta-1,4-mannanases was observed within the genera Cryptococcus (1 positive strain out of 15 tested), Geotrichum (1 of 6) and Pichia (1 of 35). The highest frequency of occurrence of endo-beta-1,4-mannanases was found within the genera Stephanoascus (2 of 2) and Aureobasidium (14 of 14). Strains hydrolyzing Ostazin Brilliant Red-galactomannan were cultivated in liquid media containing 1% locust bean gum. The best producers of extracellualr endo-beta-1,4-mannanases were found to be the strains of Aureobasidium pullulans.

Cloning and sequencing of beta-mannanase gene from Bacillus subtilis NM-39

A gene encoding beta-mannanase from Bacillus subtilis NM-39 was cloned into Escherichia coli DH5 alpha by using pUC 18 and its nucleotide sequence was determined. The beta-mannanase gene was 1080 base pairs long and encoded a mature protein of 336 amino acids and a signal peptide of 24 amino acids. The deduced amino acid sequence of the cloned mannanase showed sequence homology with mannanase from alkalophilic Bacillus sp. strain AM-001 (about 50%).

Purification and characterization of an alpha-L-arabinofuranosidase from Streptomyces lividans 66 and DNA sequence of the gene (abfA)

The gene encoding an alpha-L-arabinofuranosidase (abfA) was homologously cloned in Streptomyces lividans and its DNA sequence was determined. The enzyme was purified from the cytoplasm of the hyperproducing clone S. lividans IAF116. Its M(r) was estimated by gel filtration and found to be approx. 380,000. Since SDS/PAGE indicated a native protein of M(r) 69,000, it can be concluded that the native protein consists of several subunits of that size. The pI value was 4.6. The kinetic constants determined with p-nitrophenyl alpha-L-arabinofuranoside as substrate were a Vmax of 180 units/mg of protein and a Km of 0.6 mM. The specific activity of the purified enzyme on this substrate was 153 units/mg of protein. Optimal enzyme activity was obtained at 60 degrees C and pH 6.0. The enzyme cleaved p-nitrophenyl alpha-L-arabinofuranoside, but had no activity on a variety of other p-nitrophenyl glycosides, except on p-nitrophenyl beta-D-xylopyranoside. The enzyme showed no activity on oat-spelts (Avena sativa) xylan or arabinogalactan, but acted on beet (Beta) arabinan or arabinoxylan. Hydrolysis occurred on arabino-oligoxylosides obtained from oat-splets xylan after digestion with xylanases. Since S. lividans normally does not secrete arabinofuranosidase, this enzyme may play a role in the assimilation of arabinose moieties from arabinose-containing xylo-oligosaccharides generated by beta-xylosidases or xylanases.

Cloning and characterization of the abfB gene coding for the major alpha-L-arabinofuranosidase (ABF B) of Aspergillus niger

Based on amino-acid sequence data from Aspergillus niger alpha-L-arabinofuranosidase B (ABF B), and cyanogen bromide fragments derived thereof, deoxyoligonucleotide mixtures were designed to be employed as primers in a polymerase chain reaction (PCR) on A. niger genomic DNA. This resulted in amplification of three related PCR products. The abfB gene encoding ABF B was isolated from a genomic library using such an amplification product as a probe. A 5.1-kb BamHI fragment was subcloned to result in plasmid pIM991. Upon introduction by co-transformation into both A. niger and A. nidulans uridine auxotrophic strains, pIM991 was shown to contain the functional gene since prototrophic transformants overproduced ABF B upon growth on the inducing carbon source sugar beet pulp. A plate assay was developed enabling quick selection of ABF B-overproducing transformants. The sequence of a 4122-bp long BamHI/SstI fragment was determined. The abfB gene does not contain introns and codes for a protein of 499 amino acids. The mature ABF B, 481 amino acids in length, has a deduced molecular weight of 50.7 kDa. A. niger abfB is the first eukaryotic gene encoding an ABF to be characterized.

Mode of action of the xylan-degrading enzymes from Aspergillus awamori on alkali-extractable cereal arabinoxylans

Alkali-extractable cereal arabinoxylan and oligosaccharides of known structure derived from it by enzymic hydrolysis were treated with endo-(1-->4)-beta-D-xylanases I and III from Aspergillus awamori CMI 142717 and the digests subjected to analysis by high performance anion-exchange chromatography. Clear differences in the mode of action of the two endo-(1-->4)-beta-D-xylanases were observed. When counting from the reducing end, at least one unsubstituted xylopyranosyl residue adjacent to singly substituted xylopyranosyl residues or two unsubstituted xylopyranosyl residues adjacent to doubly substituted xylopyranosyl residues cannot be removed by endo-(1-->4)-beta-D-xylanase I. At least two unsubstituted xylopyranosyl residues adjacent to singly or doubly substituted xylopyranosyl residues cannot be removed by endo-(1-->4)-beta-D-xylanase III. beta-D-Xylosidase from the same xylanolytic system was able to remove terminal xylopyranosyl residues from the nonreducing end of branched oligosaccharides only when two contiguous unsubstituted xylopyranosyl residues were present adjacent to singly or doubly substituted xylopyranosyl residues.

Purification and Characterization of Alkaline Xylanases from Bacillus polymyxa

By applying different classical and fast protein liquid chromatographic techniques, three xylanases (β-1,4- d -xylan xylanhydrolase) were purified to homogeneity from the extracellular enzymatic complex of Bacillus polymyxa . The three enzymes (X 34 C, X 34 E, and X 22 ) were small proteins of 34, 34, and 22 kDa and basic pIs 9.3, >9.3, and 9.0, respectively. X 34 C and X 34 E are closely related and seem to be isoforms of the same enzyme. However, they differ in some characteristics. The three enzymes had different pH and temperature optima. One of them, X 34 E, showed a high thermal stability. The V max values determined for X 34 C, X 34 E, and X 22 enzymes on oat spelts xylan were 14.9, 85.5, and 64.0 U mg -1 , respectively, and 16.1, 62.0, and 150.6 U mg -1 on birchwood xylan. When oat spelts xylan was the substrate used, K m values of 3.4, 2.4, and 1.9 mg ml -1 were obtained for X 34 C, X 34 E, and X 22 enzymes, respectively, and 0.65, 6.3, and 0.32 mg ml -1 were the respective K m values determined with birchwood xylan as the substrate. The enzymes were nondebranching endo-β-xylanases. Xylose was one of the products of xylan hydrolysis by xylanases X 34 C and X 34 E, but this monosaccharide was not released by X 22 enzyme. However, neither of the enzymes was able to degrade xylobiose.

Conditions of formation, purification, and characterization of an alpha-galactosidase of Trichoderma reesei RUT C-30

Trichoderma reesei RUT C-30 formed an extracellular alpha-galactosidase when it was grown in a batch culture containing lactose or locust bean gum as a carbon source. Short-chain alpha-galactosides (melibiose, raffinose, stachyose), as well as the monosaccharides galactose, dulcitol, arabinose, and arabitol, also induced alpha-galactosidase activity both when they were used as carbon sources (at a concentration of 1%) in batch cultures and in resting mycelia (at concentrations in the millimolar range). The addition of 50 mM glucose did not affect the induction of alpha-galactosidase formation by galactose. alpha-Galactosidase from T. reesei RUT C-30 was purified to homogeneity from culture fluids of galactose-induced mycelia. The active enzyme was a 50 +/- 3-kDa, nonglycosylated monomer which had an isoelectric point of 5.2. It was active against several alpha-galactosides (p-nitrophenyl-alpha-D-galactoside, melibiose, raffinose, and stachyose) and galactomannan (locust bean gum) and was inhibited by the product galactose. It released galactose from locust bean gum and exhibited synergism with T. reesei beta-mannanase. Its activity was optimal at pH 4, and it displayed broad pH stability (pH 4 to 8). Its temperature stability was moderate (60 min at 50 degrees C resulted in recovery of 70% of activity), and its highest level of activity occurred at 60 degrees C. Its action on galactomannan was increased by the presence of beta-mannanase.

The xylan-degrading enzyme system of Talaromyces emersonii: novel enzymes with activity against aryl beta-D-xylosides and unsubstituted xylans

Talaromyces emersonii, a thermophilic aerobic fungus, produces a complete xylan-degrading enzyme system when grown on appropriate substrates. In this paper we present the physicochemical and catalytic properties of three enzymes, xylosidase (Xyl) I (M(r) 181,000; pI 8.9), II (M(r) 131,000; pI 5.3) and III (M(r) 54,200; pI 4.2). Xyl I and II appear to be dimeric and Xyl III is a single-subunit protein. All three enzymes catalyse the hydrolysis of aryl beta-D-xylosides and xylo-oligosaccharides. Xyl I is a classic beta-xylosidase (1,4-beta-D-xylan xylohydrolase; EC 3.2.1.37), and Xyl II and III are novel xylanases (endo-1,4-beta-D-xylan xylanohydrolase; EC 3.2.1.8) which we believe have not hitherto been reported. In addition to the above substrates, they also catalyse the extensive hydrolysis of unsubstituted xylans, and may have considerable biotechnological potential. The hydrolysis product profiles and bond-cleavage frequencies with various substrates are presented.

Properties of thermostable hemicellulolytic enzymes from Thermomonospora strain 29 grown in solid state fermentation on coffee processing solid waste

During decaffeination of Coffee Processing Plant Solid Wastes (CPSW) by actinomycetes, Thermomonospora, Strain 29 exhibited high titers of cellulase and xylanase. This organism, originally isolated on soybean seed coat was grown in solid state fermentation on CPSW supplemented with mineral salts. Enzymes recovered were arabinosidase, xylanase, and beta-D-xylosidase. Higher activity of the former two enzymes was in the extracellular broth, whereas the beta-D-xylosidase activity was highest in the cell fraction. The enzymes were characterized after precipitation with (NH(4))(2)SO(4), dialysis, and gel filtration. Production of all three enzymes was inhibited by monomeric sugars and sugar alcohols but not by arabinoxylan, xylans, or xylan containing water insoluble carbohydrates. The optimum pH for the activity was 6.5, 7.0, and 7.5 for beta-xylosidase, xylanase and arabinosidase (alpha-L-arabinofuranosidase, alpha-arabinosidase, alpha-L-arabinosidase) respectively. These enzymes were stable in the pH range of 6.5 to 8.0. All three enzymes were thermostable up to 80 degrees C. At 55 degrees C, arabinosidase had the longest half life of 120 h. However, at 40 degrees C, xylanase had the longest half life (504 h). At either temperature, beta-D-xylosidase had the shortest half life. The molecular weights (kDa), and Kms (mM) were estimated to be 95, 0.27; 45, 12.4; and 106, 0.67 for arbinosidase, xylanase, and beta-xylosidase respectively. Step wise addition of the three enzymes showed higher saccharification of lignocellulosics.