Showing papers on "Xylanase published in 1984"

Removing Hemicellulose from Pulps by Specific Enzymic Hydrolysis

Abstract: The hemicellulose content (solubility in 18% NaOH) of a delignified mechanical aspen pulp was lowered from 23.4% to 18.2% by one-hour hydrolysis with xylanase isolated from the fungus Schizophpllum commune by fractional precipitation. After 24 h hydrolysis, the hemicellulose content was reduced further to 12.9%. The predominant hydrolysis products, xylose and xylobiose, confirmed the specificity of hydrolysis. A crude mixture of cellulolytic and hemicellulolytic enzymes from the same microorganism gave glucose as the major hydrolysis product, and a pulp with higher relative hemicellulose content. Xylan-specific hydrolysis of a low-yield sulfite pulp gave only a small decrease in pentosan content.

Production and Properties of Extracellular Endoxylanase from Neurospora crassa

Abstract: Neurospora crassa 870 produced 14 and 0.025 U of extracellular xylanase (1,4-beta-d-xylan xylanohydrolase; EC 3.2.1.8) and beta-xylosidase (1,4-beta-xylan xylohydrolase; EC 3.2.1.37) per ml, respectively, in 4 days when commercial xylan was used as a carbon source. The effects of pH and carbon sources on xylanase production by N. crassa are discussed. Two xylanases (I and II) were purified and had pI values of 4.8 and 4.5 and molecular weights of 33,000 and 30,000. The maximum degree of hydrolysis of xylan by the extracellular culture broth was 66% in 4 h. The end products of xylan hydrolysis by xylanase I and II showed the presence of xylose, xylobiose, xylotriose, xylotetraose, xylopentose, and arabinose, indicating that they are endoxylanases capable of hydrolyzing 1,3-alpha-l-arabinofuranosyl branch points. Both xylanases showed activity toward carboxymethyl cellulose but no activity toward para-nitrophenyl-beta-d-xyloside or laminarin. Xylanase I showed appreciable activity toward para-nitrophenyl-beta-d-glucoside, whereas xylanase II was inactive.

Bioconversion of xylan to triglycerides by oil-rich yeasts.

Abstract: A series of lipid-accumulating yeasts was examined for their potential to saccharify xylan and accumulate triglyceride. Of the genera tested, including Candida, Cryptococcus, Lipomyces, Rhodosporidium, Rhodotorula, and Trichosporon, only Cryptococcus and Trichosporon isolates saccharified xylan. All of the strains could assimilate xylose and accumuate triglyceride under nitrogen-limiting conditions. Strains of Cryptococcus albidus were found to be especially useful for a one-step saccharification of xylan coupled to triglyceride synthesis. Cryptococcus terricolus, a strain constitutive for lipid accumulation, lacked extracellular xylanase, but did assimilate xylose and xylobiose and was able to continuously convert xylan to triglyceride if the culture medium was supplemented with xylanase.

Production and properties of two types of xylanases from alkalophilic thermophilic Bacillus spp.

Abstract: Four strains (W1, W2, W3, and W4) of alkalophilic thermophilic bacteria which produced xylanase were isolated from soils They were aerobic, spore-forming, Gram-positive, and rod-shaped bacteria and hence identified as the genus Bacillus The optimal temperatures for growth of the four strains were between 45° C and 50° C and pH optima were between 90 and 100 No growth occurred below pH 70 or above 55° C The four strains produced xylanases in medium containing xylan or xylose under these conditions The optimal pH and temperature for activities of the four xylanases ranged from 60 to 70 and from 65° C to 70° C, respectively The four xylanases were stable in the wide pH range from 45 to 105 at 45° C for 1 h All xylanases split xylan to yield xylose and xylobiose

Isolation of two β‐xylosidase genes of Bacillus pumilus and comparison of their gene products

Abstract: The chromosomal DNA fragments of Bacillus pumilus IPO, a potent xylan-hydrolyzing bacterium, were ligated to a vector plasmid, pBR322, and used to transform Escherichia coli C600 cells. Two hybrid plasmids, pOXD28 and pOXN29, were found to enable the transformants to produce beta-xylosidase. The former was found to contain a 2.6-MDa Bg/II fragment and the latter, a 7.7-MDa PstI fragment, both coding beta-xylosidase, but xylanase is coded only on the latter hybrid plasmid. The DNAs inserted in both plasmids originated from the B. pumilus chromosome, but from different regions, as shown by Southern hybridization and the analysis of restriction fragments. beta-Xylosidases I and II, coded on pOXN29 and pOXD28 respectively, were purified to homogeneous preparations and compared. Both were dimer enzymes consisting of 65000-70000-Da subunits. Specific activity and the Km value of beta-xylosidase I to p-nitrophenyl beta-D-xyloside as substrate were respectively 100 and 1/40 times those of beta-xylosidase II. The mobilities of beta-xylosidases I and II on polyacrylamide gel electrophoresis were also different. beta-Xylosidase I, the gene of which is located near the xylanase gene on pOXN29, can convert xylooligosaccharides to xylose, but beta-xylosidase II had little activity on xylobiose. These results suggest that beta-xylosidase I is the main enzyme for xylan hydrolysis in B. pumilus.

Bioconversion of Xylan to triglycerides by oil-rich yeasts. [Cryptococcus albidus; Cryptococcus terricoluus; Trichosporon]

Abstract: A series of lipid-accumulating yeasts was examined for their potential to saccharify xylan and accumulate triglyceride. Of the genera tested, including Candida, Cryptococcus, Lipomyces, Rhodosporidium, Rhodotorula, and Trichosporon, only Crytococcus and Trichosporon isolates saccharified xylan. All of the strains could assimilate xylose and accumuate triglyceride under nitrogen-limiting conditions. Strains of Cryptococcus albidus were found to be especially useful for a one-step saccharification of xylan coupled to triglyceride synthesis. Crytococcus terricolus, a strain constitutive for lipid accumulation, lacked extracellular xylanase, but did assimilate xylose and xylobiose and was able to continuously convert xylan to triglyceride if the culture medium was supplemented with xylanase. 22 references.

Multiplicity of Cell Wall Degrading Glycosidic Hydrolases Produced by Apple Infecting Botrytis cinerea

Abstract: It was shown that Botrytis cinerea, an isolate infecting apples, secreted in vivo and in culture a variety of glycosidic hydrolases with substrate specificity towards the polysaccharides of cell walls. The following enzymes were partially separated by column chromatography on DEAE-Sepharose CL-6B: two cellulases, three xylanases, one arabinanase, polygalacturonase, β-glucosidase, β-xylosidase, β-galactosidase, β-mannosidase and α-galactosidase. The activity of glycosidic hydrolases tested was strongly inactivated by NBS and weaker by PCMB, tetranitromethan, dibromoacetophenon and Fe3+, The results indicate synergistic action of the obtained cellulase, xylanase, polygalacturonase and arabinanase in apple cell wall degradation.

Cellulase and xylanase production by Trichoderma reesei Rut C-30

Abstract: When grown on cellulose or xylan, Trichoderma reesei (strain Rut C-30) produced extra-cellular enzymes which could hydrolyze both cellulose and xylan to their respective monosaccharides. At low O2 saturation, β -glucosidase activity is greatly reduced for cellulose-grown but not xylan-grown cells.

Cell Wall Cementing Materials of Grass Leaves

Abstract: Treatment of grass leaves with either a purified pectin lyase of Aspergillus japonicus or a purified xylanase of Trichoderma viride could lead to the isolation of some single leaf cells. However, a mixture of pectin lyase and xylanase brought about more rapid isolation of single cells than did either of the two enzymes alone, indicating a synergistic effect. Analysis of the components released from oat cell walls by the enzymes indicated that both homogalacturonans with a high degree of esterification and a kind of glucuronoarabinoxylan with ferulic acid ester may play a role in cell wall cementing in grass leaves.

Process for treating papermaking pulps with an enzyme solution promoting fibrillation and pulps thus treated

Abstract: Process for treating chemical papermaking pulps by means of an enzyme solution containing xylanases, characterised in that the said enzyme solution: - on the one hand, does not exhibit any cellulose activity; - on the other hand, is at a xylanase concentration by weight of between 0.001 % and 0.1 % of the dry weight of the pulp. Application: refining of chemical papermaking pulps.

Studies on xylan degrading enzyme from Chainia

Abstract: The sclerotial actinomycete Chainia (NCL 82-5-1) secreted extracellular xylanase in submerged culture in media containing yeast extract and wheat bran or commercial xylan. A high activity (28 IU/ml) of xylanase was obtained in 72 h on a medium containing 3% xylan. Only a single species of xylanase (i.e. without isoenzymes) was detected by polyacrylamide gel electrophoresis. It had an optimum pH of 5.0 and optimum temperature of 65°C. It was stable at pH 6.0 to heating at 60°C for 10 min. Its pI was 8.0 and the Km was 0.4%. The results are discussed in relation to xylanase reported from actinomycetes such as Streptomyces xylophagus.

Enzymic Dissociation of Zea Shoot Cell Wall Polysaccharides : III. Purification and Partial Characterization of an Endo-(1 → 4)-β-d-Xylanase from a Bacillus subtilis Enzyme Preparation

Abstract: An endo-(1 → 4)-β-xylanase [(1 → 4)-β-d-xylan 4-xylanohydrolase, EC 3.2.1.8)] has been isolated from a commercial preparation of Bacillus subtilis α-amylase (Novo Ban 120). The purified xylanase exhibited an optimum activity at pH 5.5, and maximum activity at a temperature of 50°C. The enzyme digests a (1 → 4)-β-d-xylan from larch yielding 4-linked xylobiose and xylotriose as predominant products but does not hydrolyze 4-linked xylotriose and xylobiose. The enzyme also digests a (1 → 3), (1 → 4)-β-d-mixed linkage sequence xylan from Rhodymenia into 4-linked xylobiose and xlyotriose, and 3,4-mixed linked oligosaccharides having a degree of polymerization of four or more. It is concluded that this enzyme is capable of hydrolyzing sequences of four or more (1 → 4)-β-d-linked xylose residues.

Plasmid, method for construction of the same, microorganism carrying the plasmid and method for cultivation of the microorganism

Abstract: A novel plasmid pCX311, which was constructed from Bacillus sp. C125 chromosomal DNA carrying the gene for extracellular production of xylanase and a vector plasmid pBR322. A novel microorganism, Escherichia coli HB101 (pCX311) carrying the plasmid pCX311 and being capable of extracellular production of xylanase. Method for culturing the microorganism characterized by cultivation of it in the medium containing NaCl (or KCl) and bran, or NaCl (or KCl) and xylan for 12-48 hours. According to this invention, useful high-molecular substances can be produced in a high yield.

Properties and applications of Penicillium funiculosum cellulase immobilized on a soluble polymer

Abstract: The cellobiase and xylanase activities of Penicillium funiculosum were immobilized on a soluble polymer poly(vinyl alcohol) (PVA). The kinetic parameters and the adsorption characteristics of the bound and free enzymes were compared. The Km value of the immobilized preparation was the same as the free enzyme. The hydrolysis of different cellulosic substrates by the bound enzyme is investigated.

Cell wall-degrading enzymes produced by Penicillium oxalicum Curie et Thom

Abstract: Penicillium oxalicum Curie et Thom produced an exo-polygalacturonase, an endo-polygalacturonase and an endo-pectate lyase. It also produced cellulase Cx, cellobiase, B-glucosidase, xylanase, galactanase and arabinanase in culture and in infected yam tissues. The exo-polygalacturonase was unstable. It has a molecular weight of about 38 000 daltons. The endopolygalacturonase and endo-pectate lyase had an optimal pH of 5.0 and 8.5 and an isoelectric point (pI) at pH 3.6 and 4.9 respectively. Molecular weights of both enzymes were about 28 500 and 30 000 daltons respectively. The end products of the reaction were oligogalacturonides and revealed that cellulose was degraded to glucose, with cellobiose as an intermediate product. The end products of the degradation of hemicelluloses were xylose, galactose and arabinose.

Effect of dilution on carboxymethylcellulase and xylanase assays

Abstract: It has been demonstrated that the dilution of samples prior to the carboxymethylcellulase and xylanase assays causes serious discrepancies in the numerical values obtained for the enzyme activities. Even when the sample is assayed with the identical procedure, one could obtain different numerical values of the enzyme activity U depending on how much this sample has been diluted before the enzyme assay. Two crude commercial cellulase samples of Aspergillus niger and Trichoderma viride as well as the culture filtrate of our newly isolated acidophilic fungus have been used for the demonstration. An empirical method for reporting the cellulolytic activity by taking into account this dilution effect is proposed.

Production of polysaccharide degrading enzymes by Cochliobolus sativus and Fusarium culmorum grown in liquid culture

Abstract: Cochliobolus sativus and Fusarium culmorum produced pectin degrading enzymes, xylanase and carboxymethylcellulase when grown in a salts medium with an appropriate carbon source. There was little difference in enzyme production by the two organisms except for the greatly enhanced endo-polymethylgalacturonase activity when F. culmorum was grown with citrus pectin as the carbon source. When grown on powdered wheat straw, xylanase and carboxy-methylcellulase activities were not present until the late stages of incubation. It is suggested that degradation of pectin and xylan may be as important as cellulolysis in the saprophytic survival of these organisms.

Use of Pretreated Lignocellulose for the Production of Cellulases

Abstract: Tests made to utilize lignocellulosics as a substrate for the production of cellulases showed that the enzyme production from steam and explosion decompressed aspen wood (SED) by Tricoderma reesei RUT-C30 was low, and the enzyme system produced was deficient in exoglucanase and β-glucosidase activities. Mixing this substrate with 10–20% pure cellulose lessened this deficiency and improved enzyme production. The enzyme system produced from the mixed substrate was rich in xylanase and had saccharifying ability equal to that produced in medium containing pure cellulose.

Growth and enzyme production by Aspergillus terreus in holocellulose

Abstract: Summary 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.

The Talaromyces emersonii enzyme system: biodegradation of lignocellulosic materials

Abstract: In typical fermentations at 45‡C on cellulose/corn steep liquor/ammonium and mineral salts medium, growth of the thermophilic fungusTalaromyces emersonii increases rapidly up to about 50 h and then decreases, presumably because of cell lysis, sporulation, or both. The accumulation of cellulase activity follows closely on growth and essentially reaches a maximum at about the same time that cell protein does. By contrast, two peaks of Β-glucosidase activity are observed, one maximal at about 36 h and the second at about 75 h. Fractionation of culture filtrates showed that the cellulase system is comprised of at least four endoglucanases (EC 3.2.1.4), four or five exoglucanases (cello-biohydrolase; EC 3.2.1.91), and three types of Β-glucosidase (cellobiase; EC 3.2.1.21). All are glycoproteins. Indeed, variation in carbohydrate content may account for some of the observed multiplicity of enzyme forms. Although none of the individual components is active against cellulose, reconstitution experiments show that appropriate mixtures of each type act synergistically to effect hydrolysis of substrate. In addition to the three extracellular Β-glucosidases I (Mr, 135,000), II (Mr, 100,000), and III (Mr, 45,700), an intracellular form, IV (Mr, 57,600), has been isolated. All exist as single polypeptides. The extracellular forms I and III are most active at 70‡C, pH 5, and have half-lives under these conditions of 6 and 3 h, respectively. By contrast, the intracellular form (IV) is most active at 35‡C and is rapidly denatured at higher temperatures. Substrate specificity and other studies provide clues to their possible roles in vivo. Β-Glucosidase III acts as an exoglucohydrolase by removing glucose residues from cellooligosaccharides arising from the action of endocellulases. Β-Glucosidase I is the major enzyme involved in cleaving cellobiose and short chain cellooligosaccharides. In doing so it relieves the inhibition by cellobiose of cellulase action. The intracellular form, Β-glucosidase IV, may have a dual role. By virtue of its transferase activity it may convert incoming cellobiose to the active inducer of cellulase synthesis, whereas by cleaving cellobiose to glucose (hydrolase action) it provides energy for the cell and a repressor of cellulase formation. Four endocellulases have been purified to apparent homogeneity as judged by electrophoresis. Preliminary results show that they all have Mr values of about 70,000 and pI values less than 4. However, they differ from one another in carbohydrate content, thermal stability, and affinity for substrate. The complete cellulase system is most active at pH 4.2, 60–65‡C, and retains about 80% of its original activity after 5 d incubation at 60‡C, pH 5. Avicel and filter paper most effectively induce synthesis of the complete cellulase system, as measured by the ability of culture filtrate to digest filter paper. Cotton, Solka floc, and α-cellulose are also effective inducers, as are “wastes” such as newspaper, straw, and beet pulp. Little or no cellulase synthesis is evident when lactose, cellobiose, or glucose replaces cellulose in growth media. From a practical viewpoint we find that saccharification of beet pulp is most readily achieved by using enzyme (i.e., culture filtrate) obtained by growing the organism on medium containing beet pulp as the source of cellulose. Of the various strains ofTalaromyces emersonii investigated for cellulase production, we found CBS 814.70 to be the best, yielding approx. 0.5 IU/mL of culture filtrate. By medium optimization and genetic manipulation we have isolated a number of mutants of this strain giving 2 IU/mL or more and enzyme productivities of 20–25 IU/L/h. Xylanase, arabinogalactanase, and pectinase activities have also been detected in culture filtrates of the organism when grown on beet pulp. Various lignocellulosic materials, including cotton, Solka floc, Avicel, filter paper, newspaper, and straw, can be degraded by the enzyme system. However, much of our effort has been directed to investigation of the saccharification of beet pulp since it is available in large quantities at central locations and because its lignin content is low. About 85% of the dry weight of this material is accounted for by cellulose, hemicellulose, and pectin in roughly equal proportions. Culture filtrates effect significant saccharification of pulp as measured by the release of reducing sugars or of glucose. Ball-milling the pulp prior to incubation with enzyme effects considerable improvement in the extent of digestion. Alkali or peracetic acid pretreatment of the ball-milled substrate facilitates enzymic hydrolysis even further. Good results are also obtained when unmilled pulp is (a) pretreated with pectinase prior to incubation with normal culture filtrates or (b) incubated with more concentrated culture filtrates with good pectinase activity. Under suitable conditions, 80% hydrolysis of beet pulp polysaccharides was achieved in 5 d at 60‡C, pH 5.