Physicochemical and catalytic properties of a low-molecular-weight endo-1,4-β-d-xylanase from Myrothecium verrucaria

Bioactives and Extracellular Enzymes Obtained from Fermented Macrofungi Cultivated in Cotton and Jatropha Seed Cakes

This work focused on obtaining fermented oil cake (cotton or Jatropha) via macrofungi growth with potential characteristics for animal feed formulations, such as the presence of extracellular enzymes, bioactive (ergosterol and antioxidants), and detoxification of antinutritional compounds. The concentration of phorbol esters was reduced by four macrofungi in Jatropha seed cake (JSC) to non-toxic levels. At least two macrofungi efficiently degraded free gossypol in cottonseed cake (CSC). Fermentation with Coriolopsis sp. INPA1646 and Tyromyces sp. INPA1696 resulted in increased ergosterol concentrations, antioxidant activity reduction, and high activity of laccases and proteases. Bromatological analysis indicated high crude protein concentrations, with partial solubilization by fungal proteases. Fermented products from Coriolopsis sp. and Tyromyces sp. in JSC or CSC can be considered important biological inputs for monogastric and polygastric animal feed.

Chemometrics and genome mining reveal an unprecedented family of sugar acid-containing fungal nonribosomal cyclodepsipeptides

Xylomyrocins, a unique group of nonribosomal peptide secondary metabolites, were discovered in Paramyrothecium and Colletotrichum spp. fungi by employing a combination of high-resolution tandem mass spectrometry (HRMS/MS)-based chemometrics, comparative genome mining, gene disruption, stable isotope feeding, and chemical complementation techniques. These polyol cyclodepsipeptides all feature an unprecedented d-xylonic acid moiety as part of their macrocyclic scaffold. This biosynthon is derived from d-xylose supplied by xylooligosaccharide catabolic enzymes encoded in the xylomyrocin biosynthetic gene cluster, revealing a novel link between carbohydrate catabolism and nonribosomal peptide biosynthesis. Xylomyrocins from different fungal isolates differ in the number and nature of their amino acid building blocks that are nevertheless incorporated by orthologous nonribosomal peptide synthetase (NRPS) enzymes. Another source of structural diversity is the variable choice of the nucleophile for intramolecular macrocyclic ester formation during xylomyrocin chain termination. This nucleophile is selected from the multiple available alcohol functionalities of the polyol moiety, revealing a surprising polyspecificity for the NRPS terminal condensation domain. Some xylomyrocin congeners also feature N-methylated amino acid residues in positions where the corresponding NRPS modules lack N-methyltransferase (M) domains, providing a rare example of promiscuous methylation in the context of an NRPS with an otherwise canonical, collinear biosynthetic program.

Purification and characterization of a new xylanase from Acrophialophora nainiana

A new xylanase activity (XynII) was isolated from liquid state cultures of Acrophialophora nainiana containing birchwood xylan as carbon source. XynII was purified to apparent homogeneity by gel filtration and ion exchange chromatographies. The enzyme was optimally active at 55 degrees C and pH 7.0. XynII had molecular mass of 22630+/-3.0 and 22165 Da, as determined by mass spectrometry and SDS-PAGE, respectively. The purified enzyme was able to act only on xylan as substrate. The apparent K(m) values on soluble and insoluble birchwood xylans were 40.9 and 16.1 mg ml(-1), respectively. The enzyme showed good thermal stability with half lives of 44 h at 55 degrees C and ca. 1 h at 60 degrees C The N-terminal sequence of XynII showed homology with a xylanase grouped in family G/11. The enzyme did not show amino acid composition similarity with xylanases from some fungi and Bacillus amyloliquefaciens.

Partitioning of xylanolitic complex from Penicillium janthinellum by an aqueous two-phase system

This work evaluates the influences of five parameters (pH, PEG molecular mass, PEG concentration, concentration of buffer K2HPO4-KH2PO4 and NaCl concentration) on xylanolitic complex partitioning produced by P. janthinellum in aqueous two-phase systems, using a 2(5) factorial experimental design. A mathematical model to quantify the influence of these parameters was attained and statistically tested. The optimum point for total protein extraction was obtained under the following conditions: pH 7.0, PEG 10 000, 3.67% PEG, 10% potassium phosphate and 12.4% NaCl. The partition coefficient (K) value experimentally obtained was 5.25 and that predicted by the model was 5.89.

Purification and characterization of a low molecular weight xylanase from solid-state cultures of Aspergillus fumigatus Fresenius

A xylan-degrading enzyme (xylanase II) was purified to apparent homogeneity from solid-state cultures of Aspergillus fumigatus Fresenius. The molecular weight of xylanase II was found to be 19 and 8.5 kDa, as estimated by SDS-PAGE and gel filtration on FPLC, respectively. The purified enzyme was most active at 55 °C and pH 5.5. It was specific to xylan. The apparent Km and Vmax values on soluble and insoluble xylans from oat spelt and birchwood showed that xylanase II was most active on soluble birchwood xylan. Studies on hydrolysis products of various xylans and xylooligomers by xylanase II on HPLC showed that the enzyme released a range of products from xylobiose to xylohexaose, with a small amount of xylose from xylooligomers, and presented transferase activity.

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.

Purification and characterization of two low molecular mass alkaline xylanases from Fusarium oxysporum F3

Two low molecular mass endo-1,4-beta-D-xylanases from Fusarium oxysporum were purified to homogeneity by gel-filtration and ion-exchange chromatography. They exhibit molecular masses of 20.8 (xylanase I) and 23.5 (xylanase II) kDa, and isoelectric points of 9.5 and 8.45-8.70, respectively. Both xylanases display remarkable pH (9.0) stability. At 40 to 55 degrees C xylanase II is more thermostable than xylanase I but less active on xylan. In contrast to xylanase I, xylanase II is able to hydrolyze 1-O-4-methylumbelliferyl-beta-D-glucopyranosyl)-beta-D-xylopyranoside (muxg). Neither of these enzymes hydrolyze xylotriose. They bind on crystalline cellulose but not on insoluble xylan. Analysis of reaction mixtures by high pressure liquid chromatography revealed that both enzymes cleave preferentially the internal glycosidic bonds of xylopentaose and oat spelts xylan. Thus the purified enzymes appeared to be true endo-beta-1,4-xylanases. The amino terminal sequences of xylanases I and II show to homology. Xylanase I shows high similarity with alkaline low molecular mass xylanases of family G/11.

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.

Purification and characterization of a beta-glucosidase from solid-state cultures of Humicola grisea var. thermoidea

The thermophilic fungus Humicola grisea var. thermoidea produced beta-glucosidase activity when grown in a solid-state culture on wheat bran as carbon source. A beta-glucosidase was purified to apparent homogeneity by ultrafiltration, gel filtration chromatography on Sephacryl S-100, and ion-exchange chromatography on S-Sepharose, as judged by sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE) on a 12.5% (w/v) slab gel. The enzyme had a molecular mass of 82 and 156 kDa, as estimated by SDS-PAGE and gel filtration on a high performance liquid chromatographic column, respectively, suggesting that the native enzyme may consist of two identical subunits. The purified enzyme was thermostable at 60 degrees C for 1 h with a half-life of 15 min at 65 degrees C, and displayed optimum activity at 60 degrees C and a pH range. of 4.0-4.5. The Km and Vmax values for p-nitrophenyl beta-D-glucopyranoside were determined to be 0.316 mM and 0.459 IU.mL-1, respectively. D-Glucose, D-gluconic acid lactone, Hg2+, Cu2+, and Mn2+ inhibited beta-glucosidase activity. The enzyme activity was competitively inhibited by D-glucose (ki = 0.6 mM). The purified enzyme was very active against cellobiose and p-nitrophenyl beta-D-glucopyranoside.