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PubMed2001

Microbial xylanases and their industrial applications: a review.

Despite an increased knowledge of microbial xylanolytic systems in the past few years, further studies are required to achieve a complete understanding of the mechanism of xylan degradation by microorganisms and their enzymes. The enzyme system used by microbes for the metabolism of xylan is the most important tool for investigating the use of the second most abundant polysaccharide (xylan) in nature. Recent studies on microbial xylanolytic systems have generally focussed on induction of enzyme production under different conditions, purification, characterization, molecular cloning and expression, and use of enzyme predominantly for pulp bleaching. Rationale approaches to achieve these goals require a detailed knowledge of the regulatory mechanism governing enzyme production. This review will focus on complex xylan structure and the microbial enzyme complex involved in its complete breakdown, studies on xylanase regulation and production and their potential industrial applications, with special reference to biobleaching.

Bacteria↗
PubMed1996

Purification and characterisation of a major xylanase with cellulase and transferase activities from Fusarium oxysporum.

A major xylanase from Fusarium oxysporum was purified to homogeneity by gel filtration, affinity, and ion-exchange chromatographies. It has a molecular mass of 60.2 kDa and pI of 6.6 and was optimally active at pH 7.4 and at 50 degrees C. The enzyme was stable over the pH range 5.8-8.2 at 40 degrees C for 24 h and lost 45% of its original activity at pH 9.0 under the identical conditions. The enzyme rapidly hydrolysed xylans from oat spelts (husks) and birchwood, but the activities on carboxymethylcellulose (CMC), filter paper, and Avicel were very low. Determination of kcat/Km revealed that the enzyme hydrolysed oat spelts and birchwood xylans, 15-30 times more efficiently than CMC. In a 24 h incubation, at pH 7.0 and 9.0, the enzyme hydrolysed oat spelts and birchwood xylans by 75 and 65%, respectively. However, at pH 7.0, the enzyme released almost equal amounts of xylose and xylobiose from both xylans, whereas at pH 9.0, the concentration of xylobiose was twice as muchi as that of xylose and xylotriose. Xylanase attacked preferentially the internal glycosidic bonds of xylo- and 4-methylumbelliferyl cello-oligosaccharides [MeUmb(Glc)n]. The enzyme catalysed transglycosylation reaction with xylotriose, xylotetraose, and xylopentaose as donors and 4-methylumbelliferyl beta-D-glucoside (MeUmbGlc) as an acceptor.

Cellulase↗
PubMed2005

Molecular cloning and characterization of a novel beta-1,3-xylanase possessing two putative carbohydrate-binding modules from a marine bacterium Vibrio sp. strain AX-4.

We cloned a novel beta-1,3-xylanase gene, consisting of a 1728-bp open reading frame encoding 576 amino acid residues, from a marine bacterium, Vibrio sp. strain AX-4. Sequence analysis revealed that the beta-1,3-xylanase is a modular enzyme composed of a putative catalytic module belonging to glycoside hydrolase family 26 and two putative carbohydrate-binding modules belonging to family 31. The recombinant enzyme hydrolysed beta-1,3-xylan to yield xylo-oligosaccharides with different numbers of xylose units, mainly xylobiose, xylotriose and xylotetraose. However, the enzyme did not hydrolyse beta-1,4-xylan, beta-1,4-mannan, beta-1,4-glucan, beta-1,3-xylobiose or p-nitrophenyl-beta-xyloside. When beta-1,3-xylo-oligosaccharides were used as the substrate, the kcat value of the enzyme for xylopentaose was found to be 40 times higher than that for xylotetraose, and xylotriose was extremely resistant to hydrolysis by the enzyme. A PSI-BLAST search revealed two possible catalytic Glu residues (Glu-138 as an acid/base catalyst and Glu-234 as a nucleophile), both of which are generally conserved in glycoside hydrolase superfamily A. Replacement of these two conserved Glu residues with Asp and Gln resulted in a significant decrease and complete loss of enzyme activity respectively, without a change in their CD spectra, suggesting that these Glu residues are the catalytic residues of beta-1,3-xylanase. The present study also clearly shows that the non-catalytic putative carbohydrate-binding modules play an important role in the hydrolysis of insoluble beta-1,3-xylan, but not that of soluble glycol-beta-1,3-xylan. Furthermore, repeating a putative carbohydrate-binding module strongly enhanced the hydrolysis of the insoluble substrate.

Amino Acid Sequence↗
PubMed2000

Isolation, purification and characterization of xylanasefrom Staphylococcus sp. SG-13 and its application in biobleaching of kraft pulp.

A haloalkalophilic Staphylococcus sp. SG-13 produced an alkalistable xylanase in wheat bran medium. A 12-fold purification was achieved by using standard purification techniques. The purified xylanase exhibited a dual pH optima of 7.5 and 9.2. The optimum temperature for enzyme activity was 50 degrees C. The enzyme was stable at 50 degrees C for more than 4 h. The xylanase exhibited Km and Vmax values of 4 mg ml-1, 90 micromol min-1 per mg for birchwood xylan and 7 mg ml-1, 55 micromol min-1 per mg for oatspelt xylan, respectively. The substrate binding affinity of xylanase was more for oatspelt xylan but birchwood xylan was hydrolysed more rapidly. The xylanase activity was stimulated by Fe2+, Ni2+, Cu2+ and dithiothreitol up to 60% and was strongly inhibited in the presence of Co2+, Hg2+, Pb2+, phenyl methane sulphonyl fluoride, ethylenediaminetetraacetic acid, and acetic anhydride up to 100%. The xylanase dose of 1.8 U g-1 moisture free pulp, exhibited bleach boosting of kraft pulps optimally at pH 9.5-10.0 and 50 degrees C after 4 h of reaction time. Pretreatment of pulp with xylanase and its subsequent treatment with 8% hypochlorite, reduced the kappa number by 30%, enhanced the brightness and viscosity by 11% and 1.8%, respectively, and improved the paper properties such as tensile strength and burst factor up to 10% and 17%, respectively.

Chlorine Compounds↗
PubMed2000

A novel Cellvibrio mixtus family 10 xylanase that is both intracellular and expressed under non-inducing conditions.

Hydrolysis of the plant cell wall polysaccharides cellulose and xylan requires the synergistic interaction of a repertoire of extracellular enzymes. Recently, evidence has emerged that anaerobic bacteria can synthesize high levels of periplasmic xylanases which may be involved in the hydrolysis of small xylo-oligosaccharides absorbed by the micro-organism. Cellvibrio mixtus, a saprophytic aerobic soil bacterium that is highly active against plant cell wall polysaccharides, was shown to express internal xylanase activity when cultured on media containing xylan or glucose as sole carbon source. A genomic library of C. mixtus DNA, constructed in lambdaZAPII, was screened for xylanase activity. The nucleotide sequence of the genomic insert from a xylanase-positive clone that expressed intracellular xylanase activity in Escherichia coli revealed an ORF of 1137 bp (xynC), encoding a polypeptide with a deduced M(r) of 43413, defined as xylanase C (XylC). Probing a gene library of Pseudomonas fluorescens subsp. cellulosa with C. mixtus xynC identified a xynC homologue (designated xynG) encoding XylG; XylG and xynG were 67% and 63% identical to the corresponding C. mixtus sequences, respectively. Both XylC and XylG exhibit extensive sequence identity with family 10 xylanases, particularly with non-modular enzymes, and gene deletion studies on xynC supported the suggestion that they are single-domain xylanases. Purified recombinant XylC had an M(r) of 41000, and displayed biochemical properties typical of family 10 polysaccharidases. However, unlike previously characterized xylanases, XylC was particularly sensitive to proteolytic inactivation by pancreatic proteinases and was thermolabile. C. mixtus was grown to late-exponential phase in the presence of glucose or xylan and the cytoplasmic, periplasmic and cell envelope fractions were probed with anti-XylC antibodies. The results showed that XylC was absent from the culture media but was predominantly present in the periplasm of C. mixtus cells grown on glucose, xylan, CM-cellulose or Avicel. These data suggest that C. mixtus can express non-modular internal xylanases whose potential roles in the hydrolysis of plant cell wall components are discussed.

Cell Wall↗
PubMed1993

Purification and characterization of a new xylanase (APX-II) from the fungus Aureobasidium pullulans Y-2311-1.

Aureobasidium pullulans Y-2311-1 produced four major xylanases (EC 3.2.1.8) with pI values of 4.0, 7.3, 7.9, and 9.4 as revealed by isoelectric focusing and zymogram analysis when grown for 4 days on 1.0% oat spelt xylan. The enzyme with a pI of 9.4 was purified by ammonium sulfate precipitation, chromatography on a DEAE-Sephadex A-50 column, and gel filtration with a Sephadex G-75 column. The enzyme had a mass of about 25 kDa as determined by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography. The purified enzyme had a Km of 7.6 mg . ml(-1) and Vmax of 2,650 micromol . min(-1) . mg(-1) for birchwood xylan at 28 degrees C and pH 4.5. It lacked activity towards carboxymethylcellulose, cellobiose, starch, mannan, p-nitrophenyl (pNP)-beta-D-xylopyranoside, pNP-beta-D-glucopyranoside, pNP-alpha-D-glucopyranoside, pNP-beta-D-cellobioside, pNP-beta-D-fucopyranoside, or pNP-alpha-D-galactopyranoside. The predominant end products of birchwood xylan or xylohexaose hydrolysis were xylobiose and xylose. The enzyme had the highest activity of pH 4.8 and 54 degrees C. Sixty percent of the activity remained after the enzyme had been incubated at 55 degrees C and pH 4.5 for 30 min. The sequence of the first 68 amino acid residues at the amino terminus showed homology to those of several other xylonases. Immunoblot analysis with antiserum raised against the purified xylanase revealed that two immunologically related polypeptides of 25 and 22 kDa were produced in A. pullulans cultures containing oat spelt xylan or xylose as carbon sources but not in cultures containing glycerol or glucose.

Amino Acid Sequence↗
PubMed1994

Enzymatic specificities and modes of action of the two catalytic domains of the XynC xylanase from Fibrobacter succinogenes S85.

The xylanase XynC of Fibrobacter succinogenes S85 was recently shown to contain three distinct domains, A, B, and C (F. W. Paradis, H. Zhu, P. J. Krell, J. P. Phillips, and C. W. Forsberg, J. Bacteriol. 175:7666-7672, 1993). Domains A and B each bear an active site capable of hydrolyzing xylan, while domain C has no enzymatic activity. Two truncated proteins, each containing a single catalytic domain, named XynC-A and XynC-B were purified to homogeneity. The catalytic domains A and B had similar pH and temperature parameters of 6.0 and 50 degrees C for maximum hydrolytic activity and extensively degraded birch wood xylan to xylose and xylobiose. The Km and Vmax values, respectively, were 2.0 mg ml-1 and 6.1 U mg-1 for the intact enzyme, 1.83 mg ml-1 and 689 U mg-1 for domain A, and 2.38 mg ml-1 and 91.8 U mg-1 for domain B. Although domain A had a higher specific activity than domain B, domain B exhibited a broader substrate specificity and hydrolyzed rye arabinoxylan to a greater extent than domain A. Furthermore, domain B, but not domain A, was able to release xylose at the initial stage of the hydrolysis. Both catalytic domains cleaved xylotriose, xylotetraose, and xylopentaose but had no activity on xylobiose. Bond cleavage frequencies obtained from hydrolysis of xylo-alditol substrates suggest that while both domains have a strong preference for internal linkages of the xylan backbone, domain B has fewer subsites for substrate binding than domain A and cleaves arabinoxylan more efficiently. Chemical modification with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide methiodide and N-bromosuccinimide inactivated both XynC-A and XynC-B in the absence of xylan, indicating that carboxyl groups and tryptophan residues in the catalytic site of each domain have essential roles.

Amino Acid Sequence↗
PubMed2006

Standard assays do not predict the efficiency of commercial cellulase preparations towards plant materials.

Commercial cellulase preparations are potentially effective for processing biomass feedstocks in order to obtain bioethanol. In plant cell walls, cellulose fibrils occur in close association with xylans (monocotyls) or xyloglucans (dicotyls). The enzymatic conversion of cellulose/xylans is a complex process involving the concerted action of exo/endocellulases and cellobiases yielding glucose and xylanases yielding xylooligomers and xylose. An overview of commonly measured cellulase-, cellobiase-, and xylanase-activity, using respectively filter paper, cellobiose, and AZCL-dyed xylan as a substrate of 14 commercially available enzyme preparations from several suppliers is presented. In addition to these standardized tests, the enzyme-efficiency of degrading native substrates was studied. Grass and wheat bran were fractionated into a water unsoluble fraction (WUS), which was free of oligosaccharides and starch. Additionally, cellulose- and xylan-rich fractions were prepared by alkaline extraction of the WUS and were enzymatically digested. Hereby, the capability of cellulose and xylan conversion of the commercial enzyme preparations tested was measured. The results obtained showed that there was a large difference in the performance of the fourteen enzyme samples. Comparing all results, it was concluded that the choice of an enzyme preparation is more dependent on the characteristics of the substrate rather than on standard enzyme-activities measured.

Biological Assay↗
PubMed2002

Crystal structures of the sugar complexes of Streptomyces olivaceoviridis E-86 xylanase: sugar binding structure of the family 13 carbohydrate binding module.

The family 10 xylanase from Streptomyces olivaceoviridis E-86 contains a (beta/alpha)(8)-barrel as a catalytic domain, a family 13 carbohydrate binding module (CBM) as a xylan binding domain (XBD) and a Gly/Pro-rich linker between them. The crystal structure of this enzyme showed that XBD has three similar subdomains, as indicated by the presence of a triple-repeated sequence, forming a galactose binding lectin fold similar to that found in the ricin toxin B-chain. Comparison with the structure of ricin/lactose complex suggests three potential sugar binding sites in XBD. In order to understand how XBD binds to the xylan chain, we analyzed the sugar-complex structure by the soaking experiment method using the xylooligosaccharides and other sugars. In the catalytic cleft, bound sugars were observed in the xylobiose and xylotriose complex structures. In the XBD, bound sugars were identified in subdomains alpha and gamma in all of the complexes with xylose, xylobiose, xylotriose, glucose, galactose and lactose. XBD binds xylose or xylooligosaccharides at the same sugar binding sites as in the case of the ricin/lactose complex but its binding manner for xylose and xylooligosaccharides is different from the galactose binding mode in ricin, even though XBD binds galactose in the same manner as in the ricin/galactose complex. These different binding modes are utilized efficiently and differently to bind the long substrate to xylanase and ricin-type lectin. XBD can bind any xylose in the xylan backbone, whereas ricin-type lectin recognizes the terminal galactose to sandwich the large sugar chain, even though the two domains have the same family 13 CBM structure. Family 13 CBM has rather loose and broad sugar specificities and is used by some kinds of proteins to bind their target sugars. In such enzyme, XBD binds xylan, and the catalytic domain may assume a flexible position with respect to the XBD/xylan complex, inasmuch as the linker region is unstructured.

Binding Sites↗
PubMed2003

Characterization of a Paenibacillus cell-associated xylanase with high activity on aryl-xylosides: a new subclass of family 10 xylanases.

The sequence of gene xynB encoding xylanase B from Paenibacillus sp. BP-23 was determined. It revealed an open reading frame of 999 nucleotides encoding a protein of 38,561 Da. The deduced amino acid sequence of xylanase B shows that the N-terminal region of the enzyme lacks the features of a signal peptide. When the xylan-degrading system of Paenibacillus sp. BP-23 was analysed in zymograms, it revealed that xylanase B was not secreted to the extracellular medium but instead remained cell-associated, even in late stationary-phase cultures. When xynB was expressed in a Bacillus subtilis secreting host, it also remained associated with the cells. Sequence homology analysis showed that xylanase B from Paenibacillus sp. BP-23 belongs to family 10 glycosyl hydrolases, exhibiting a distinctive high homology to six xylanases of this family. The homologous enzymes were also found to be devoid of a signal peptide and seem to constitute, together with xylanase B, a separate group of enzymes. They all have two conserved amino acid regions not found in the other family 10 xylanases, and cluster in a separate group after dendrogram analysis. We propose that these enzymes constitute a new subclass of family 10 xylanases, that are cell-associated, and that hydrolyse the xylooligosaccharides resulting from extracellular xylan hydrolysis. Xylanase B shows similar specific activity on aryl-xylosides and xylans. This can be correlated to some, not yet identified, trait of catalytic activity of the enzyme on plant xylan.

Amino Acid Sequence↗
PubMed2005

Xylanases from fungi: properties and industrial applications.

Xylan is the principal type of hemicellulose. It is a linear polymer of beta-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to 4-O-methyl-alpha-D-glucuronopyranosyl units, acetyl groups, alpha-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-beta-xylanase and beta-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.

Endo-1,4-beta Xylanases↗
PubMed2004

Thermostable xylanase10B from Clostridium acetobutylicum ATCC824.

The Clostridium acetobutylicum xylanase gene xyn10B (CAP0116) was cloned from the type strain ATCC 824, whose genome was recently sequenced. The nucleotide sequence of C. acetobutylicum xyn10B encodes a 318-amino acid protein. Xyn10B consists of a single catalytic domain that belongs to family 10 of glycosyl hydrolases. The enzyme was purified from recombinant Escherichia coli. The Xyn10B enzyme was highly active toward birchwood xylan, oat-spelt xylan, and moderately active toward avicel, carboxymethyl cellulose, polygalacturonic acid, lichenan, laminarin, barley-beta-glucan and various p-nitrophenyl monosaccharides. Xyn10B hydrolyzed xylan and xylooligosaccharides to produce xylobiose and xylotriose. The pH optimum of Xyn10B was 5.0, and the optimal temperature was 70 degrees C. The enzyme was stable at 60 degrees C at pH 5.0-6.5 for 1 h without substrate. This is one of a number of xylan-related activities encoded on the large plasmid in C. acetobutylicum ATCC 824.

Cloning, Molecular↗
PubMed1979

On the specificity and mode of action of a xylanase from Trametes hirsuta (Wulf.) Pilát.

The mode of action of the extracellular endo-(1 leads to 4)-beta-D-xylanase produced by Trametes hirsuta on a (4-0-methyl-D-glucurono)-D-xylan and a modified, essentially neutral D-xylan from white willow (Salix alba L.) has been studied. Xylotetraose and xylohexaose, together with aldotetraouronic and aldohexaouronic acids, were the main products. The acidic oligosaccharides had a 4-O-methyl-D-glucopyranosyluronic acid group attached to the non-reducing D-xylosyl end-group. The action pattern of the xylanase corresponds to that of a typical endo-enzyme that acts more readily in the middle of chain, and the specific region of its action appears to involve five D-xylosyl residues. The products of the enzymic treatment of the D-xylan have revealed a regular distribution of the 4-O-methyl-D-glucopyranosyluronic acid groups attached to the D-xylan backbone.

Basidiomycota↗
PubMed2004

Purification and characterization of thermostable xylanase and beta-xylosidase by the thermophilic bacterium Bacillus thermantarcticus.

Bacillus thermantarcticus, a thermophilic bacterium isolated from Antarctic geothermal soil near the crater of Mount Melbourne, produced extracellular xylanase (1,4-beta-D-xylan xylanohydrolase; E.C. 3.2.1.8) and beta-xylosidase (1,4-beta-D-xylan xylohydrolase; E.C. 3.2.1.37). Each extracellular enzyme was separated by gel filtration with Sephacryl S-200 and further purified to homogeneity (119-fold for xylanase and 160-fold for beta-xylosidase). The optimum temperatures were 80 degrees C for xylanase at pH 5.6 and 70 degrees C for beta-xylosidase at pH 6.0. The isoelectric points and molecular masses were 4.8 and 45 kDa for xylanase and 4.2 and 150 kDa for beta-xylosidase, respectively. Xylanase was stable at 60 degrees C for 24 h, whereas it showed a half life at 70 degrees C of 24 h and at 80 degrees C for 50 min. beta-xylosidase activity did not decrease after 1 h at 60 degrees C. Km of xylanase for xylan was 1.6 mg/ml, Km of beta-xylosidase for p-nitrophenyl-beta-D-xylopyranoside was 0.5 mM and for o-nitrophenyl-beta-D-xylopyranoside was 1.28 mM. The action of two enzymes on xylan gave only xylose.

Geobacillus stearothermophilus↗
PubMed1989

Structural changes in cellobiohydrolase I upon binding of a macromolecular ligand as evident by SAXS investigations.

Xylan from Rhodymenia palmata binds to the cellobiohydrolase I from Trichoderma reesei (CBH I) or its core protein, inhibiting their activity. Adsorption onto microcrystalline cellulose (Avicel) is reduced approximately 30% for intact CBH I and nearly 50% for the core, whereas the effects with cellobiose are negligible. Structural changes concomitant with this binding are studied in solution by small angle X-ray scattering. In the "tadpole" structure typical for the CBH I [Abuja et al., 1988] the lengthening of the tail part is the most salient observation when xylan is present which accounts for an increase in Dmax (18.0 to 22.0 nm) and radius of gyration (4.74 to 5.18 nm). When xylan binds to the core the radius of gyration remains nearly unchanged. Here a model can be constructed showing a xylan molecule on the surface of the core protein near the tail part.

Adsorption↗
PubMed2003

Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Sporotrichum thermophile.

An endo-beta-1,4-xylanase (1,4-beta-D-xylan xylanoxydrolase, EC 3.2.1.8) present in culture filtrates of Sporotrichum thermophile ATCC 34628 was purified to homogeneity by Q-Sepharose and Sephacryl S-200 column chromatographies. The enzyme has a molecular mass of 25,000 Da, an isoelectric point of 6.7, and is optimally active at pH 5 and at 70 degrees C. Thin-layer chromatography (TLC) analysis showed that endo-xylanase liberates mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methylglucuronoxylan and rhodymenan (a beta-(1-->4)-beta(1-->3)-xylan). Also, the enzyme releases an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. Analysis of reaction mixtures by high performance liquid chromatography (HPLC) revealed that the enzyme cleaves preferentially the internal glycosidic bonds of xylooligosaccharides, [1-3H]-xylooligosaccharides and xylan. The enzyme also hydrolyses the 4-methylumbelliferyl glycosides of beta-xylobiose and beta-xylotriose at the second glycosidic bond adjacent to the aglycon. The endoxylanase is not active on pNPX and pNPC. The enzyme mediates a decrease in the viscosity of xylan associated with a release of only small amounts of reducing sugar. The enzyme is irreversibly inhibited by series of omega-epoxyalkyl glycosides of D-xylopyranose. The results suggest that the endoxylanase from S. thermophile has catalytic properties similar to the enzymes belonging to family 11.

Catalysis↗
PubMed1998

Enzymatic specificity and hydrolysis pattern of the catalytic domain of the xylanase Xynl from Rhodothermus marinus.

The catalytic domain of a xylanase from Rhodothermus marinus was produced in Escherichia coli. The catalytic domain belongs to glycosyl hydrolase family 10. The produced protein has a 22-amino acid leader peptide followed by a 411-amino acid truncated xylanase. The molecular mass was 48 kDa and the recombinant xylanase had a pI of 4.9. The pH and temperature optima for activity were determined to be 7.5 and 80 degrees C, respectively. At that temperature the enzyme had a half-life of 1 h 40 min. An addition of 1 mM calcium stabilized the activity of the enzyme at 80 degrees C. The xylanase had its highest specific activity on oat spelt xylan but was active also on other xylans and to a limited extent on some other polysaccharides (soluble glucans). No exo- or endo-cellulase activity was observed. Hydrolysis of xylo-oligomers and oat spelt xylan was studied and the predominant products of hydrolysis were xylobiose and xylotriose. The enzyme was inactive on xylobiose, xylotriose and on the soluble fraction from oat spelt xylan. The R. marinus xylanase is shown to have a strong preference for internal linkages and is therefore classified as an endo-xylanase.

Amino Acid Sequence↗
PubMedDate not supplied

Growth and enzyme production by Aspergillus terreus in holocellulose.

The growth of Aspergillus terreus Thom in holocellulose medium and the production of xylanase and cellulolytic enzymes were studied and compared with growth and enzyme production in xylan and cellulose powder media. Hemicellulose and cellulose were utilized simultaneously by the fungus when grown in holocellulose medium. The growth was similar in the presence of xylan and cellulose powder, but xylan was consumed earlier than cellulose. Cellulose powder, carboxymethylcellulase and xylanase activity reached a maximum earlier in cellulose powder and xylan medium than in holocellulose medium.

Aspergillus↗