Biosynthesis of fructo-oligosaccharides by Sporotrichum thermophile during submerged batch cultivation in high sucrose media.

Biosynthesis of fructo-oligosaccharides (FOS) was observed during growth of the thermophilic fungus Sporotrichum thermophile on media containing high sucrose concentrations. Submerged batch cultivation with the optimum initial sucrose concentration of 250 g/l allowed the production of 12.5 g FOS/l. The FOS mixture obtained was composed of three sugars, which were isolated by size-exclusion chromatography. They were characterized by acid hydrolysis and HPLC as 1-kestose, 6-kestose and neokestose. The mechanism of osmotic adaptation of S. thermophile was investigated and sugars and amino acids were found to be the predominant compatible solutes. The fungus accumulated glutamic acid, arginine, alanine, leucine and lysine, in order to balance the outer osmotic pressure. Fatty acid analysis of the membrane lipids showed a relatively high percentage of unsaturated lipids, which is known to be associated with high membrane fluidity.

Purification and characterization of a feruloyl esterase from Fusarium oxysporum catalyzing esterification of phenolic acids in ternary water-organic solvent mixtures.

An extracellular feruloyl esterase (FAE-II) from the culture filtrates of Fusarium oxysporum F3 was purified to homogeneity by SP-Sepharose, t-butyl-HIC and Sephacryl S-200 column chromatography. The protein corresponded to molecular mass and pI values of 27 kDa and 9.9, respectively. The enzyme was optimally active at pH 7 and 45 degrees C. The purified esterase was fully stable at pH 7.0-9.0 and temperature up to 45 degrees C after 1 h incubation. Determination of k(cat)/K(m) revealed that the enzyme hydrolysed methyl sinapinate 6, 21 and 40 times more efficiently than methyl ferulate, methyl coumarate and methyl caffeate, respectively. The enzyme was active on substrates containing ferulic acid ester linked to the C-5 but inactive to the C-2 positions of arabinofuranose such as 4-nitrophenyl 5-O-trans-feruloyl-alpha-L-arabinofuranoside and 4-nitrophenyl 2-O-trans-feruloyl-alpha-L-arabinofuranoside. In the presence of Sporotrichum thermophile xylanase, there was a significant release of ferulic acid from destarched wheat bran by FAE-II, indicating a synergistic interaction between FAE-II and S. thermophile xylanase. FAE-II by itself could release only little ferulic acid from destarched wheat bran. The potential of FAE-II for the synthesis of various phenolic acid esters was tested using as a reaction system a surfactantless microemulsion formed in ternary mixture consisting of n-hexane, 1-propanol and water.

Performance of an intermittent agitation rotating drum type bioreactor for solid-state fermentation of wheat straw.

A laboratory bioreactor, designed for solid-state fermentation of thermophilic microorganisms, was operated for production of cellulases and hemicellulases by the thermophilic fungus Thermoascus aurantiacus. The suitability of the apparatus for the effective control of important operating variables affecting growth of microbes in solid-state cultivation was determined. Application of the optimum conditions found for the moisture content of the medium, growth temperature and airflow rate produced enzyme yields of 1709 U endoglucanase, 4 U cellobiohydrolase, 79 U beta-glucosidase, 5.5 U FPA, 4490 U xylanase and 45 U beta-xylosidase per g of dry wheat straw. The correlation between microorganism growth and production of enzymes was efficiently described by the Le Duy kinetic model.

Antimicrobial activity of acidic xylo-oligosaccharides produced by family 10 and 11 endoxylanases.

Acidic oligosaccharides were obtained from birchwood xylan by treatment with a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. The main difference between the products liberated by xylanases of family 10 and 11 concerned the length of the products containing 4-O-methyl-D-glucuronic acid. The xylanase from T. aurantiacus liberate from glucuronoxylan an aldotetrauronic acid as the shortest acidic fragment in contrast with the enzyme from S. thermophile, which liberated an aldopentauronic acid. Acidic xylooligosaccharides were separated from the hydrolysate by anion-exchange and size-exclusion chromatography (SEC) and the primary structure was determined by 13C NMR spectroscopy. The acidic xylo-oligosaccharides were tested against three Gram-positive and three Gram-negative aerobically grown bacteria, as well as against Helicobacter pylori. Aldopentauronic acid was proved more active against the Gram-positive bacteria and against H. pylori.

Purification and characterization of an extracellular alpha-L-arabinofuranosidase from Fusarium oxysporum.

An alpha-L-arabinofuranosidase from Fusarium oxysporum F3 was purified to homogeneity by a two-step ion exchange intercalated by a gel filtration chromatography. The enzyme had a molecular mass of 66 kDa and was optimally active at pH 6.0 and 60 degrees C. It hydrolyzed aryl alpha-L-arabinofuranosides and cleaved arabinosyl side chains from arabinoxylan and arabinan. There was a marked synergistic effect between the alpha-L-arabinofuranosidase and an endo-(1-->4)-beta-D-xylanase produced by F. oxysporum in the extensive hydrolysis of arabinoxylan.

Purification and mode of action of an alkali-resistant endo-1, 4-beta-glucanase from Bacillus pumilus.

Alkaline endo-1,4-beta-d-glucanase was secreted by Bacillus pumilus grown in submerged culture on a combination of oat spelt xylan and corn starch as carbon sources. The enzyme was purified to homogeneity by Sephacryl S-200 and Q-Sepharose column chromatography. The protein corresponded to molecular mass and pI values of 67 kDa and 3.7, respectively. The enzyme was optimally active at pH 7.0-8.0 and 60 degrees C and retained 50% of its optimum activity at pH 12. The most notable characteristic of the endoglucanase was its high stability up to pH 12 for 20 h at 30 degrees C. The enzyme hydrolyzed carboxymethylcellulose (CMC) and cello-oligosaccharides but was inactive on cellobiose, cellotriose, Avicel, xylan, 4-nitrophenyl-beta-d-glucoside, 4-nitrophenyl-beta-d-cellobioside, and 4-nitrophenyl-beta-d-xyloside. Analysis of reaction mixtures by HPLC revealed that the enzyme produced almost exclusively cellotriose when acted on CMC and appeared to hydrolyze cello-oligosaccharides by successively releasing cellotriose. The use of 4-methylumbelliferyl cello-oligosaccharides and the determination of bond cleavage frequency revealed that the enzyme preferentially hydrolyzed the third glycosidic bond adjacent to the glycon. The enzyme mediated a decrease in the viscosity of CMC associated with a release of only small amounts of reducing sugar. The enzyme activity was not inhibited by metal ions, surfactants, and chelating agents used as components of laundry detergents.

Mode of action of a minor xylanase from Thermoascus aurantiacus on polysaccharides and model substrates.

The mode of action of a minor xylanase on a variety of polysaccharides and model substrates was investigated. The enzyme was excreted by Thermoascus aurantiacus grown in solid state fermentation (SSF). The purified enzyme had a molecular mass of 33,000. Thin layer chromatography analysis showed that the endoxylanase liberated short fragments from polysaccharides. The enzyme hydrolysed aryl-beta-D-cellobioside and the chromogenic (fluorogenic) 4-methylumbelliferyl-beta-glycosides of xylobiose (MeUmbXyl2) and xylotriose (MeUmbXyl3) at the agluconic linkage. The results suggested that the endoxylanase belonged to family 10.

A novel lipolytic activity of Rhodotorula glutinis cells: production, partial characterization and application in the synthesis of esters.

Cell-bound lipase activity (10 pNPL units/g dry cell weight) was released when the yeast Rhodotorula glutinis was cultured in a 7-l stirred tank fermentor using palm-oil as the sole carbon source. The enzyme showed relative specificity towards medium chain organic acids since the apparent K(m) values for pNPB (p-NitroPhenyl-Butyrate) and pNPL (p-NitroPhenyl-Laurate) were equal to 2.7 and 0.7 mM, respectively. In addition, 80% of this activity could be detected on the surface of the cells. The cell-bound nature of the enzyme increased its thermal stability showing half-life times of 200 and 60 min at 50 and 60 degrees C, respectively, as well as good stability in organic solvents. Freeze-dried cell preparations were successfully used to catalyze the synthesis of fatty acid esters of butanol and heptanol in nearly anhydrous organic solvents. A conversion of 60-62% was obtained upon esterification of palmitic or oleic acid with butanol, within 96 h. The enzyme preparation was used in four consecutive batch reactions with only 10% loss of activity.

Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Thermomyces lanuginosus ATCC 46882.

An endoxylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) from the culture filtrates of T. lanuginosus ATCC 46882 was purified to homogeneity by DEAE-Sepharose and Bio-Gel P-30 column chromatographies. The purified endoxylanase had a specific activity of 888.8 mumol min-1 mg-1 protein and accounted for approximately 30% of the total protein secreted by this fungus. The molecular mass of native (non-denatured) and denatured endoxylanase were 26.3 and 25.7 kD as, respectively. Endoxylanase had a pI of 3.7 and was optimally active between pH 6.0-6.5 and at 75 degrees C. The enzyme showed > 50% of its original activity between pH 5.5-9.0 and at 85 degrees C. The pH and temperature stability studies revealed that this endoxylanase was almost completely stable between pH 5.0-9.0 and up to 60 degrees C for 5 h and at pH 10.0 up to 55 degrees C for 5 h. Thin-layer chromatography (TLC) analysis showed that endoxylanase released mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methyl-D-glucuronoxylan and rhodymenan (a beta-(1-->3)-beta(1-->4)-xylan). Also, the enzyme released an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. The enzyme hydrolysed [1-3H]-xylo-oligosaccharides in an endofashion, but the hydrolysis of [1-3H]-xylotriose appeared to proceed via transglycosylation. since the xylobiose was the predominant product. Endoxylanase was not active on pNPX and pNPC at 40 and 100 mM for up to 6 h, but showed some activity toward pNPX at 100 mM after 20-24 h. The results suggested that the endoxylanase from T. lanuginosus belongs to family 11.

Factors affecting the specificity of beta-glucosidase from Fusarium oxysporum in enzymatic synthesis of alkyl-beta-D-glucosides.

Fusarium oxysporum beta-glucosidase has been used to catalyze the production of alkyl-beta-D-glucosides from various disaccharides, based on the transglucosylation reaction, in the presence of primary, secondary and tertiary alcohols as glucosyl acceptors. Primary alcohols were found to be the best acceptors. The influence of the glucosyl donor concentration, as well as the enzyme specificity towards the cleaved glucosidic bond and the aglucone part of the donor, have also been investigated. The enzyme does not exhibit regiospecificity and seems to be unspecific towards the aglucone part. The specificity of the beta linkage has been confirmed by proton nuclear magnetic resonance (1H NMR) analysis.

An efficient and optimized purification procedure for the superoxide dismutase from Aspergillus niger. Partial characterization of the purified enzyme.

Cu,Zn-superoxide dismutase was isolated from Aspergillus niger mycelia, harvested at the mid-logarithmic growth phase. The purification scheme aimed at the optimization of the ethanol/chloroform extraction (Tsuchihashi extraction) through response surface methodology. Upon optimum extraction conditions, it was possible to obtain electrophoretically pure enzyme preparations, by the application of one step anion exchange chromatography. The enzyme yield of this simple purification procedure was above 75% while the specific activity of the final preparation was among the highest reported for eucariotic microorganisms. The purified enzyme exhibited similar physicochemical characteristics with other Aspergillus sp. superoxide dismutases revealing an apparent tetrameric structure with a subunit molecular weight of 19 kDa, and a pl of 5.95.

A new glucose oxidase from Aspergillus niger: characterization and regulation studies of enzyme and gene.

A new glucose oxidase from Aspergillus niger was isolated and characterized. The enzyme showed different kinetic and stability characteristics when compared to a commercially available batch of A. niger glucose oxidase. The gene encoding the new glucose oxidase was isolated and DNA sequence analysis of the coding region showed 80% identity to the sequence of a glucose oxidase gene previously published. However, the similarity of the non-coding sequences up- and downstream of the open reading frame was much less, showing only 66% and 50% identity respectively. Despite the low degree of similarity between the promotor region of the new gene and the previously published one, the new glucose oxidase was likewise induced by calcium carbonate. In addition, we showed that this induction occurred on the transcriptional level. Observations concerning the effect of gluconolactone and the levels of glucose-6 phosphate isomerase upon calcium carbonate induction suggested that the enhancement of glucose oxidase biosynthesis by calcium carbonate was accompanied by a metabolic shift from glycolysis to the pentose phosphate pathway.

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 less randomly acting endo-1,4-beta-D-glucanase from the culture filtrates of Fusarium oxysporum.

An extracellular endo-1,4-beta-D-glucanase from Fusarium oxysporum was purified by affinity chromatography and gel filtration. The enzyme purified in this way was homogeneous when judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing-polyacrylamide gel electrophoresis. The protein corresponded to a molecular mass and pI value of 41.7 kDa and 6.4, respectively. It was optimally active at pH 4.5 and at 55 degrees C. The enzyme hydrolyzed carboxymethylcellulose (CMC) and unsubstituted and substituted cello-oligosaccharides but was inactive on Avicel, filter paper, xylan, cellobiose, p-nitrophenyl-beta-D-glucoside, and p-nitrophenyl-beta-D-xyloside. However, the enzyme effected only a small change in viscosity of CMC per unit increase of reducing sugar. When cellotriose, cellotetraose, and cellopentaose were used as substrates, the enzyme released mainly cellobiose. Use of 4-methylumbelliferyl cello-oligosaccharides and the determination of bond cleavage frequency revealed that the enzyme preferentially hydrolyzed the glycosidic bond adjacent to 4-methylumbelliferone. Thus, the purified enzyme appeared to be a less randomly acting endoglucanase.

Enzymatic synthesis of trisaccharides and alkyl beta-D-glucosides by the transglycosylation reaction of beta-glucosidase from Fusarium oxysporum.

Purified beta-glucosidase from Fusarium oxysporum catalyses hydrolysis and transglycosylation reactions. By utilizing the transglycosylation reaction, trisaccharides and alkyl beta-D-glucosides were synthesized under optimal conditions in the presence of various disaccharides and alcohols. The yields of trisaccharides and alkyl beta-D-glucosides were 22-37% and 10-33% of the total sugar, respectively. The enzyme retained 70-80% of its original activity in the presence of 25% (w/v) methanol, ethanol and propanol. Thus, beta-glucosidase from F. oxysporum appears to be an ideal enzyme for the synthesis of useful trisaccharides and alkyl beta-D-glucosides.

Purification and characterisation of an extracellular beta-glucosidase with transglycosylation and exo-glucosidase activities from Fusarium oxysporum.

An extracellular beta-glucosidase from Fusarium oxysporum was purified to homogeneity by gel-filtration and ion-exchange chromatographies. The enzyme, a monomeric protein of 110 kDa, was maximally active at pH 5.0-6.0 and at 60 degrees C. It hydrolysed 1-->4-linked aryl-beta-glucosides and 1-->4-linked, 1-->3-linked and 1-->6-linked beta-glucosides. The apparent Km and kcat values for p-nitrophenyl beta-D-glucopyranoside (4-NpGlcp) and cellobiose were 0.093 (Km), 1.07 mM (kcat) and 1802 (Km), 461.5 min-1 (kcat), respectively. Glucose and gluconolactone inhibited the enzyme competitively with Ki values of 2.05 mM and 3.03 microM, respectively. Alcohols activated the enzyme; butanol showed maximum effect (2.2-fold at 0.5 M) while methanol increased the activity by 1.4-fold at 1 M. The enzyme catalysed the synthesis of methylglucosides, ethylglucoside and propylglucosides, as well as trisaccharides in the presence of different alcohols and disaccharides, respectively. In addition, the enzyme hydrolysed the unsubstituted and methylumbelliferyl cello-oligosaccharides [MeUmb(Glc)n] but the rate of hydrolysis decreased with increasing chain length. Analysis of products released from MeUmb(Glc)n as a function of time revealed that the enzyme attacked these substrates in a stepwise manner and from both ends. Thus, beta-glucosidase from F. oxysporum, with the above interesting properties, could be of commercial interest.

Correlating the effect of pretreatment on the enzymatic hydrolysis of straw.

Avicell, Alkali-treated straw cellulose (ATSC), and wheat straw were ball-milled to reduce crystallinity; wheat straw was delignified by hot (120 degrees C) sodium hydroxide solutions of various concentrations. The physically and chemically pretreated cellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Enzymic hydrolysis data were fitted by the hyperbolic correlation of Holtzapple, which involves two kinetic parameters, the maximum conversion (X(max)), and the enzymic hydrolysis time corresponding to 50% of X(max) (t(1/2)). An empirical correlation between X(max) and cellulose crystallinity, lignin content, and degree of delignification has been found under our experimental conditions. Complete cellulose hydrolysis is shown to be possible at less than 60% crystallinity indices or less than 10% lignin content.