Showing papers on "Xylanase published in 1988"

Nucleotide sequence and deletion analysis of the xylanase gene (xynZ) of Clostridium thermocellum.

Abstract: The nucleotide sequence of the xynZ gene, encoding the extracellular xylanase Z of Clostridium thermocellum, was determined. The putative xynZ gene was 2,511 base pairs long and encoded a polypeptide of 837 amino acids. A region of 60 amino acids containing a duplicated segment of 24 amino acids was found between residues 429 and 488 of xylanase Z. This region was strongly similar to the conserved domain found at the carboxy-terminal ends of C. thermocellum endoglucanases A, B, and D. Deletions removing up to 508 codons from the 59 end of the gene did not affect the activity of the encoded polypeptide, showing that the active site was located in the C-terminal half of the protein and that the conserved region was not involved in catalysis. Expression of xylanase activity in Escherichia coli was increased up to 220-fold by fusing fragments containing the 39 end of the gene with the start of lacZ present in pUC19. An internal translational initiation site which was efficiently recognized in E. coli was tentatively identified 470 codons downstream from the actual start codon. Images

Viscosity-enhancing bleaching of hardwood kraft pulp with xylanase from a cloned gene.

Abstract: The idea of removing lignin from kraft pulp with ligninolytic microorganisms has been around for some time.' More recently, a peroxidase has been described2 which, in the presence of low concentrations of peroxide, might depolymerize lignin and, in combination with an extraction, thereby bleach kraft pulp. An alternative approach is based on reports that residual lignin in unbleached kraft pulp is linked to hemi~ellulose~ and that cleavage of this linkage will allow lignin to be r e l e a ~ e d . ~ Hydrolysis of the lignin-hemicellulose linkage would have to be specific, in order to prevent deterioration of pulp qualities, e.g. viscosity, due to cellulose hydrolysis . 5 Ideally, the ligninhemicellulose linkage itself should be the only one cleaved. In hardwoods, the linkage is mainly betwen lignin and xylan, possibly through arabinose side chain^.^" We recently produced clones of E . coli capable of endoxylanase or P-xylosidase production in the absence of cellulase,8,' which could find potential application in lignincarbohydrate cleavage, especially for hardwood kraft pulps where xylan is the predominant hemicellulose, and can even be redeposited on the pulp during cooking." We now describe experiments which demonstrate that lignin removal can, indeed, be aided by treatment with xylanase from a cloned system, and that the resulting pulp retains viscosity as well as the required strength properties.

Ferulic Acid Esterase Activity from Schizophyllum commune.

Abstract: Schizophyllum commune produced an esterase which released ferulic acid from starch-free wheat bran and from a soluble ferulic acid-sugar ester that was isolated from wheat bran. The preferred growth substrate for the production of ferulic acid esterase was cellulose. Growth on xylan-containing substrates (oat spelt xylan and starch-free wheat bran) resulted in activity levels that were significantly lower than those observed in cultures grown on cellulose. Similar observations were made for endoglucanase, p-nitrophenyllactopyranosidase, xylanase, and acetyl xylan esterase. Of the enzymes studied, only arabinofuranosidase was produced at maximum levels during growth on xylan-containing materials. Ferulic acid esterase that had been partially purified by DEAE chromatography released significant amounts of ferulic acid from wheat bran only in the presence of a xylanase-rich fraction, indicating that the esterase may not be able to readily attack high-molecular-weight substrates. The esterase acted efficiently, without xylanase addition, on a soluble sugar-ferulic acid substrate.

Remazol Brilliant Blue-xylan: A soluble chromogenic substrate for xylanases

Abstract: Publisher Summary The conjugate of the polysaccharide with the dye, abbreviated as Remazol Brilliant Blue-Xylan (RBB-xylan), represents a convenient substrate for determination of activity and detection of xylanases. This chapter describes assay method that is based on photometric measurements of the enzyme released dyed fragments soluble in the presence of two volumes of ethanol that precipitates the original substrate and its high-molecular-weight fragments. This principle offers to measure xylanase activity in cell-free extracts and media containing larger amount of reducing compounds that would interfere with classical xylanase activity determination. Xylanase activity on the cell surface and on isolated membranes and organelles can be followed in the presence of viable cells consuming xylose and xylooligosaccharides. The detection of xylanase activity in gels employs transparent agar replicas containing RBB-xylan. Diffusion of dyed fragments released in the place of the enzyme into the separation gel or their selective removal from the agar replicas by the solvent system used for the precipitation of unhydrolyzed RBB-xylan in a solution, represents the basis for enzyme detection. A great advantage of the technique is that the substrate present in a 2% agar gel does not precipitate as it does in a solution, so that the agar replicas remain transparent during and after the destaining of the zones of the enzyme-depolymerized substrate.

Production of xylanase by the ruminal anaerobic fungus Neocallimastix frontalis.

Abstract: Xylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) production was investigated in the ruminal anaerobic fungus Neocallimastix frontalis. The enzyme was released principally into the culture fluid and had pH and temperature optima of 5.5 and 55 degrees C, respectively. In the presence of low concentrations of substrate, the enzyme was stabilized at 50 degrees C. Xylobiose was the principal product of xylanase action, with lesser amounts of longer-chained xylooligosaccharides. No xylose was detected, indicating that xylobiase activity was absent. Activities of xylanase up to 27 U ml-1 (1 U represents 1 micromol of xylose equivalents released min-1) were obtained for cultures grown on xylan (from oat spelt) at 2.5 mg ml-1 in shaken cultures. No growth occurred in unshaken cultures. Xylanase production declined with elevated concentrations of xylan (less than 2.5 mg ml-1), and this was accompanied by an accumulation of xylose and, to a lesser extent, arabinose. Addition of either pentose to cultures grown on low levels of xylan in which neither sugar accumulated suppressed xylanase production, and in growth studies with the paired substrates xylan-xylose, active production of the enzyme occurred during growth on xylan only after xylose had been preferentially utilized. When cellobiose, glucose, and xylose were tested as growth substrates for the production of xylanase (each initially at 2.5 mg ml-1), they were found to be less effective than xylan, and use of xylan from different origins (birch wood or larch wood) as the growth substrate or in the assay system resulted in only marginal differences in enzyme activity. However, elevated production of xylanase occurred during growth on crude hemicellulose (barley straw leaf). The results are discussed in relation to the role of the anaerobic fungi in the ruminal ecosystem, and the possible application of the enzyme in bioconversion processes is also considered.

Effect of phenolic monomers on the growth and beta-glucosidase activity of Bacteroides ruminicola and on the carboxymethylcellulase, beta-glucosidase, and xylanase activities of Bacteroides succinogenes.

Abstract: trans-p-Coumaric acid inhibited the growth of Bacteroides ruminicola on both cellobiose and glucose, while trans-ferulic acid and vanillin retarded growth. The phenolic monomers varied in their potential to inhibit the Bacteroides succinogenes beta-glucosidase, carboxymethylcellulase, and xylanase, with p-coumaric acid being the most inhibitory. The B. ruminicola beta-glucosidase was inhibited less than 10% by all three compounds.

Factors Influencing Protoplast Viability of Suspension-Cultured Rice Cells during Isolation Process

Abstract: Callus cells of rice (Oryza sativa L.) that were actively dividing in suspension culture had lost the ability to divide during the isolation process of protoplasts. Factors influencing the protoplast viability were examined using highly purified preparations of cellulase C1, xylanase, and pectin lyase, which were essential enzymes for the isolation of protoplasts from the rice cells. The treatment of the cells with xylanase and pectin lyase, both of which are macerating enzymes, caused cellular damage. Xylanase treatment was more detrimental to the cells. Osmotic stress, cell wall fragments solubilized by xylanase, and disassembly of cortical microtubules were not the primary factors which damaged the rice cells and protoplasts. The addition of AgNO3, an inhibitor of ethylene action, to the protoplast isolation medium increased the number of colonies formed from the cultured protoplasts, although the yield of protoplasts was reduced by the addition. Superoxide radical (O2-) was generated from the cells treated with xylanase or pectin lyase. The addition of superoxide dismutase and catalase to the protoplast isolation medium resulted in a marked improvement in protoplast viability especially when the non-additive control protoplasts formed colonies with a low frequency. The addition of glutathione peroxidase and phospholipase A2, which have been known to reduce and detoxify lipid hydroperoxides in membranes, to the protoplast culture medium significantly increased the frequency of colony formation. These results suggested that some of the damage to rice protoplasts may be caused by oxygen toxicity.

Sacchariiication of Straw by Actinomycete Enzymes

Abstract: SUMMARY: Over 200 strains of actinomycetes, representing nine distinct genera, were screened directly for the ability to release reducing sugar from ball-milled wheat straw, using a microtitre plate assay system. Xylanase activity was detected in nearly all of the strains examined while activities against purified cellulosic substrates were less widespread and relatively low. Straw saccharification resulted from cooperative enzyme action and sugar yields were not simply correlated with substrate particle size. Straw-saccharifying activity was further characterized in selected strains comprising five representatives of the genera Thermomonospora and Streptomyces, one Micromonospora strain and the type strain of Microbispora bispora. Common features included optimal saccharification of straw in the pH range 6.0.9.0 and xylose and its oligomers as the principal products, although low concentrations of glucose were also detected. Optimal activity and increased stability at 70°C was a feature of enzyme preparations from Thermomonospora and thermophilic Streptomyces strains. β-Xylosidase and β-glucosidase activities were largely intracellular, but significant amounts of extracellular β-xylosidase activity were also found in two strains. Other enzymes involved in straw saccharification include acetylesterase and arabinofuranosidase, and these activities were detected in all strains. Acetylesterase and arabinofuranosidase activities were largely extracellular, but in some strains significant amounts of intracellular activity were also detected.

Molecular cloning of multiple xylanase genes from Pseudomonas fluorescens subsp. cellulosa.

Abstract: Pseudomonas fluorescens subsp. cellulosa was shown to express extracellular xylanases. Genes encoding these enzymes were isolated from a gene library of P. fluorescens subsp. cellulosa DNA, constructed in bacteriophage λ47.1. One of the phages (PXC) that expressed xylanase also conferred the ability to hydrolyse carboxymethylcellulose. An 11.8 kb HindIII DNA restriction fragment and a 6.2 kb EcoRI DNA fragment were subcloned from two distinct xylanase-expressing phages, into pUC18, to yield recombinant plasmids pGHJ4 and pGHJ5 respectively. Cells of Escherichia coli harbouring either of these two plasmids, or plasmid pJHH1 (comprising the cellulase gene from PXC, previously cloned on a 7.3 kb partial EcoRI DNA fragment in pUC18), expressed xylanase activity. The positions of the xylanase genes in the recombinant plasmids were elucidated by subcloning and transposon mutagenesis. In pJHH1 the xylanase gene was adjacent to the DNA region encoding the endoglucanase. The polysaccharide-degrading genes in pJHH1 were transcribed from different promotors. Hybridization studies revealed that the xylanase genes encoded by pGHJ4 and pGHJ5 showed strong homology. All three cloned enzymes cleaved p-nitrophenyl β-D-glucopyranoside and 4-methylumbelliferyl β-D-cellobioside. Xylan and glucose did not affect expression of xylanase in E. coli strains harbouring pJHH1, pGHJ4 or pGHJ5.

Cellulases of Thermomonospora fusca

Abstract: Publisher Summary Thermomonospora fusca YX is a filamentous actinomycete that has a doubling time of about 4 hr when grown at 55° in defined medium with cellulose as a carbon source. The supernatant from a culture of cellulose-grown T. fusca contains a high level of cellulase activity, xylanase activity, and an active protease that modifies the different cellulases without altering their cellulase activity. A mutant strain of T. fusca has been isolated, ER-1, which produces no detectable extracellular protease activity, and the supernatant from this strain has been used to purify the different cellulase activities produced by T. fusca. Five different β-1,4-endoglucanases and one xylanase have been isolated from the culture supernatant of ER-1 cells grown on cellulose. This chapter describes the assay method and purification procedure of these enzymes.

Cellulose and hemicellulose

Abstract: Cellulose. Preparation of Cellulosic Substrates: Increasing the Availability of Cellulose in Biomass Materials. Cadoxen Solvolysis of Cellulose. Preparation of Crystalline, Amorphous, and Dyed Cellulase Substrates. Preparation of Cellodextrins. Preparation of Cellodextrins: Another Perspective. Fluorogenic and Chromogenic Glycosides as Substrates and Ligands of Carbohydrases. Use of Complex Formation between Congo Red and Polysaccharides in Detection and Assay of Polysaccharide Hydrolases. Soluble, Dye-Labeled Polysaccharides for the Assay of Endohydrolases. Assays for Cellulolytic Enzymes: Methods for Measuring Cellulase Activities. Cellulase Assay Based on Cellobiose Dehydrogenase. Nephelometric and Turbidometric Assay for Cellulase. Selective Assay for Exo-1,4-/-Glucosidases. Viscosimetric Determination of Carboxymethylcellulase Activity. Staining Techniques for the Detection of the Individual Components of Cellulolytic Enzyme Systems. Chromatographic Methods for Carbohydrates: Liquid Chromatography of Carbohydrate Monomers and Oligomers. Quantitative Thin-Layer Chromatography of Sugars, Sugar Acids, and Polyalcohols. High-Performance Thin-Layer Chromatography of Starch, Cellulose, Xylan, and Chitin Hydrolyzates. Miscellaneous Methods for Cellulolytic Enzymes: Screening of Prokaryotes for Cellulose- and Hemicellulose-Degrading Enzymes. Chromatographic Separation of Cellulolytic Enzymes. Morphological Aspects of Wood Degradation. Purification of Cellulose-Degrading Enzymes: Cellulases of Pseudomonas fluorescens var. cellulosa. Cellulases of Cellulomonas uda. Cellulase of Ruminococcus albus. Cellulase of Trichoderma koningii. Cellulases of Trichoderma reesei. Cellulases of a Mutant Strain of Trichoderma viride QM 9414. Cellulases from Eupenicillium javanicum. Gentaro Okada, Cellulase of Aspergillus niger. Cellulase and Hemicellulase from Aspergillus fumigatus Fresenius. Cellulases of Aspergillus aculeatus. Cellulases from Thermoascus aurantiacus. 1,4-/-*xD-Glucan Cellobiohydrolase from Sclerotium rolfsii. Cellulases of Thermomonospora fusca. Cellulases of Humicola insolens and Humicola grisea. Cellulase-Hemicellulase Complex of Phoma hibernica. Cellulases from Sporocytophaga myxococcoides. Cellulases in Phaseolus vulgaris. Endoglucanase from Clostridium thermocellum. Crystalline Endoglucanase D of Clostridium thermocellum Overproduced in Escherichia coli. Isolation of 1,4-/-*xD-Glucan 4-Glucanohydrolases of Talaromyces emersonii. Endo-1,4-/-Glucanases of Sporotrichum pulverulentum. Carboxymethylcellulase from Sclerotium rolfsii. /-Glucanases from Pisum sativum. Cellobiosidase from Ruminococcus albus. Cellobiohydrolases of Penicillium pinophilum. Exocellulase of Irpex lacteus (Polyporus tulupiferae). /-Glucosidase from Ruminococcus albus. 1,4-/-Glucosidases of Sporotrichum pulverulentum. /-*xD-Glucosidases from Sclerotium rolfsii. Purification and Assay of /-Glucosidase from Schizophyllum commune. Purification of /-*xD-Glucoside Glucohydrolases of Talaromyces emersonii. Cellobiose Dehydrogenase from Sporotrichum thermophile. Cellobiose Dehydrogenase from Sclerotium rolfsii. Cellobiose Dehydrogenase Produced by Monilia. Cellobiose Dehydrogenase (Quinone). Cellobiose Phosphorylase from Cellvibrio gilvus. Cellulosomes from Clostridium thermocellum. Macrocellulase Complexes and Yellow Affinity Substance from Clostridium thermocellum. Acid Proteases from Sporotrichum pulverulentum. Hemicellulose. Preparation of Substrates for Hemicellulases: Purification of (1-3),(1-4)-/-Glucan from Barley Flour. Synthesis of /-*xD-Mannopyranosides for the Assay of /-*xD-Mannosidase and Exo-/-*xD-mannanase. Enzymatic Preparation of /-1,4-Mannooligosaccharides and /-1,4-Glucomannooligosaccharides. Carob and Guar Galactomannans. Xylobiose and Xylooligomers. Remazol Brilliant Blue-Xylan: A Soluble Chromogenic Substrate for Xylanases. Preparation of *xL-Arabinan and 1,5-*xL-Arabinan. Analysis of /-Glucan and Enzyme Assays: Measurement of (1-3),(1-4)-/-*xD-Glucan. Measurement of Acetylxylan Esterase in Streptomyces. 4-O-Methyl-*ga-*xD-Glucuronidase Component of Xylanolytic Complexes. Lichenase from Bacillus subtilis. Purification of /-*xD-Glucosidase from Aspergillus niger. Exo-1,4-/-Mannanase from Aeromonas hydrophila. Exo-/-*xD-mannanase from Cyamopsis tetragonolobus GuarSeed. /-*xD-Mannanase. /-Mannanase of Streptomyces. /-*xD-Mannosidase from Helix pomatia. *ga-Mannanase from Rhodococcus erythropolis. *ga-*xD-Galactosidase from Lucerne and GuarSeed. Xylanase of Bacillus pumilus. Xylanase of Cryptococcus albidus. Xylanases of Streptomyces. Xylanases of Alkalophilic Thermophilic Bacillus. Xylanase A of Schizophyllum commune. Xylanases and /-Xylosidase of Trichoderma lignorum. Xylanase of Malbranchea pulchella var. sulfurea. Xylanase of Talaromyces byssochlamydoides. 1,4-/-*xD-Xylan Xylohydrolase of Sclerotium rolfsii. /-Xylosidases of Several Fungi. /-Xylosidase//-Glucosidase of Chaetomium trilaterale. Acetylxylan Esterase of Schizophyllum commune. *ga-*xL-Arabinofuranosidase from Aspergillus niger. *ga-*xL-Arabinofuranosidase from Scopolia japonica. Arabinogalactanase of Bacillus subtilis var. amylosacchariticus. Author Index. Subject Index.

Isolation and Characterization of Xylan-Degrading Strains of Butyrivibrio fibrisolvens from a Napier Grass-Fed Anaerobic Digester.

Abstract: Six new xylanolytic bacterial strains have been isolated from a Napier grass-fed anaerobic digester. These strains were identified as Butyrivibrio fibrisolvens and were similar in many respects to ruminal isolates described previously. The new isolates exhibited a high degree of DNA homology with several ruminal strains of B. fibrisolvens. Xylan or xylose was required to induce the production of enzymes for xylan degradation, xylanase and xylosidase. Production of these enzymes was repressed in the presence of glucose. Xylanase activity was predominantly extracellular, while that of xylosidases was cell associated. The new isolates of B. fibrisolvens grew well in defined medium containing xylan as the sole carbon source and did not produce obvious slime or capsular layers. These strains may be useful for future genetic investigations.

Extracellular enzyme production and cell wall degradation by freshwater lignicolous fungi

Abstract: Ten Ascomycetes, seven Fungi Imperfecti and one Oomycete known to occur on submerged wood were tested for their ability to produce amylase, xylanase, cellulases, lipase, polygalacturonase, pectin lyase, protease, chitinase, and polyphenol oxidases. Species were also tested for their ability to degrade lignosols, with and without wood sugars, and indulin, and to form soft-rot cavities on balsa, green ash, and cottonwood. With the exception of Pythium sp., species were generalists with respect to hydrolytic enzymes and could degrade a wide range of substrates. All species produced weak or negative reactions on media containing chitin and lignin derivatives. Although Nectria haematococca, N. lucidum and Heliscus lugdunensis produced strong to moderate positive reactions on xylan, carboxymethylcellulose and Walseth cellulose, they did not form soft-rot cavities. All other species except Pythium sp. produced typical soft-rot cavities.

Xylanase and β‐xylosidase production by Aspergillus ochraceus during growth on lignocelluloses

Abstract: Xylan is a polysaccharide located in the cell wall of higher plants which is one of the major components of lignocellulosic materials. In some higher plants and agricultural wastes the xylan is 20-40% of the dry material.' It consists of p-1, 4-linked D-xylose chain. The breakdown of hemicellulose is accomplished by the synergistic action of xylanase (1,4+-~-xylan xylanohydrolase, EC 3.2.1.8) and P-xylosidase (P-D-xyloside xylohydrolase, EC 3.2.1.37). Such enzymes are useful in the degradation of biomaterials containing hemicellulose for the production of monosaccharides from which single-cell protein, single-cell oil, or ethanol could be produced. '-I1 The production and properties of enzymes capable of breaking down cellulose have been extensively st~died. '~-~' Although there are reports on the production of xylanase,'8-26 the behavior of xylanases and its involvement in the utilization of complex lignocellulosic material is still incomplete. Therefore, the present communication deals with the utilization of some lignocellulosic materials by A . ochraceus for xylanase and pxylosidase production. The use of purified xylan enhances the cost of enzyme production and is a major limitation to the economic feasibility of bioconversion and utilization of lignocellulosic materials. Therefore, in this work, easily available substrates like wheat straw, wheat bran, and sugarcane bagasse were used in the experiment to obtain optimum levels of xylanases by the fungal strain A . ochruceus.

Selective solubilization of xylan in pulp using a purified xylanase from Trichoderma harzianum

Abstract: The specificity of action of a cellulase-free xylanase preparation on pulp fibers was revealed by the composition of the solubilized products after enzyme treatment. The neutral carbohydrates released by the treatment of two hardwood kraft pulps were composed exclusively of xylooligomers. A similar treatment of Solka Floc showed no detrimental effect on the degree of polymerization of the cellulose fibers, as determined by size exclusion chromatographic analysis.

Molecular Cloning and Expression of a Xylanase Gene from Bacillus polymyxa in Escherichia coli.

Abstract: Genomic fragments of Bacillus polymyxa derived from separate and complete digestion by EcoRI, HindIII, and BamHI were ligated into the corresponding sites of pBR322, and the resulting chimeric plasmids were transformed into Escherichia coli. Of 6,000 transformants screened, 1 (pBPX-277) produced a clear halo on Remazol brilliant blue xylan plates. The insert in the pBPX-277 recombinant, identified as an 8.0-kilobase BamHI fragment of B. polymyxa, was subsequently subjected to extensive mapping and a series of subclonings into pUC19. A 2.9-kilobase BamHI-EcoRI subfragment was found to code for xylanase activity. Xylanase activity expressed by E. coli harboring the cloned gene was located primarily in the periplasm and corresponded to one of two distinct xylanases produced by B. polymyxa. Xylanase expression by the cloned gene occurred in the absence of xylan and was reduced by glucose and xylose. Southern blot hybridization with the cloned fragment as a probe against complete genomic digests of the bacilli B. polymyxa, B. circulans, and B. subtilis revealed that the cloned xylanase gene was unique to B. polymyxa. The xylanase expressed by the cloned gene had a molecular weight of approximately 48,000 and an isoelectric point of 4.9.

Xylanases and β-xylosidase of Trichoderma liǵnorum

Abstract: Publisher Summary Trichoderma lignorum is a rich source of various extracellular polyand oligosaccharide-degrading enzymes—for example, xylanases, cellulase, amyloglucosidase, β-xylosidasey α-arabinosidase, and β-glucosidase. This chapter describes a simple procedure for the purification of two different xylanases, 1,4-β-D-xylan xylanohydrolase and a β-xylosidase, β-D-xyloside xylohydrolase from the culture supernatant of this fungus. Studies on the properties of these enzymes reveal that one xylanase has a remarkably high glycosyltransferase activity. The β-xylosidase is a glycoprotein and shows high thermal stability. The chapter provides a list of some of the biochemical properties of the two xylanases and the β-xylosidase. Both xylanases yield single bands after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Under the same conditions, two protein bands can be detected for the β-xylosidase that indicates that this enzyme is composed of two different subunits.

Xylanase A of Schizophyllum commune

Abstract: Publisher Summary Xylanases belong to a broader group of enzymes, hemicellulases, responsible for conversion of hemicelluloses to soluble sugars. Hemicellulases in general and xylanases in particular are also of some commercial interest. This chapter describes the assay method, production, and properties of xylanase A of Schizophyllum commune . The enzyme assay is based on the hydrolysis of larch xylan. Due to the incomplete definition of the substrate and the fact that its properties change during the assay, the results are reproducible only under carefully standardized conditions. The chapter discusses the preparation of crude xylanase by fractional precipitation. Xylanase A is assumed to be an endoxylanase although its specificity has not been studied in detail. The major hydrolysis products after 18-hr hydrolysis are xylobiose and xylose. It appears to be strictly specific for xylan; no appreciable cellulase, β-glucosidase or β-xylosidase activity has been found.

Xylanolytic enzyme activities produced by mesophilic and thermophilic actinomycetes grown on graminaceous xylan and lignocellulose

Abstract: Mesophilic and thermophilic strains of actinomycetes were grown on media containing graminaceous xylan or lignocellulose. Aliquots of the culture fluids were sampled and assayed for enzyme activities involved in the degradation of hemicellulose. Xylanase, acetyl esterase and α-arabinofuranosidase activities could be detected after different times of incubation; their production was also dependent on the growth medium. The highest levels of xylanase activity were found in cultures of strains of Streptomyces, Actinomadura sp. and Saccharomonospora viridis. Streptomyces cyaneus produced the highest amount of arabinofuranosidase whereas acetyl esterase activities were highest in S. cyaneus, S. viridis and Pseudonocardia thermophila.

Xylanase of Bacillus pumilus

Abstract: Publisher Summary Xylanase production has been reported in many microorganisms including fungi, yeasts, and bacteria. Bacillus pumilus is a microbe producing potent xylan degrading enzymes. In the laboratory, endoxylanase and β-xylosidase of B. pumilus IPO, isolated from a rice field, were purified and hydrolysis of xylan to xylose was found to be accomplished by sequential reaction of these two enzymes. A chromosomal DNA fragment of B. pumilus IPO containing genes of both enzymes was cloned in Escherichia coli and the complete DNA sequences of both genes were determined. This chapter describes the purification and properties of the xylanase of B. pumilus IPO. The purified xylanase had an activity and stability optimum at pH 6.5. The enzyme retained more than 85% of its activity after standing at 40° for 30 min at pH 8.5 or 5.0. The maximum xylanase activity was observed at temperatures between 45 and 50° over a period of 10 min.

Changes in activities of cell wall degrading enzymes during fermentation of cassava (Manihot esculenta Crantz) with citrobacter freundii

Abstract: The cell wall degrading enzymes polygalacturonase (EC 3.2.1.15),pectinase (EC 3.1.1.11), cellulose (EC 3.2.1.4) and xylanase (EC 3.2.1.8), as well as α-amylase (EC 3.2.1.1) and phosphorylase (EC 2.4.1.1), were monitored during fermentation of cassava (Manihot esculenta Crantz) with Citrobacter freundii. All the enzymes were detected in cassava at the start. During fermentation, initial decreases in polygalacturonase, cellulase and xylanase were followed by increases which peaked as the tissue softened. There were significant (P<0.05) increases in pectinase, xylanase, cellulase, polygalacturonase and phosphorylase in inoculated cassava and the fermentation medium relative to controls (uninoculated cassava and medium) during the softening period. The control cassava did not ferment, indicating that the textural changes in inoculated cassava were due to enzymes secreted by C freundii. Studies on the effect of enzyme inhibition on fermentation showed that the pectic enzymes and cellulase were of primary importance and that inhibition of α-amylase and phosphorylase had no effect on the process.

Induction and catabolite repression of cellulase inPenicillium funiculosum

Abstract: The regulation of endoglucanase synthesis inPenicillium funiculosum is investigated using a method based on the viscosity lowering effect on carboxy methyl cellulose (CMC) by endoglucanase Cellobiose (1 mg/L) causes induction, whereas glucose (5 g/L) does not repress the enzyme formation Lactose (5 g/L) has no effect on the synthesis of cellulase Avicel and cellulose powder (CP) are the best inducers of cellulase and xylanase activity Both endoglucanase and xylanase activity were induced by CMC, whereas xylan induced only xylanase activity The effect of protease on induction of cellulase activity is discussed

Amino acid composition and partial sequence of xylanase from Aureobasidium

Abstract: Although xylanases from five species showed striking similarities in amino acid composition, xylanase from the yeastAureobasidium, with exceptionally high specific activity, had an atypical composition. Nevertheless, the enzyme possessed extensive identity with a proposed amino-terminal consensus sequence.