Isolation and properties of recombinant inulinases from Aspergillus sp

The genes inuA and inu1, encoding two inulinases (32nd glycosyl hydrolase family) from filamentous fungi Aspergillus niger and A. awamori, were cloned into Penicillium canescens recombinant strain. Using chromatographic techniques, endoinulinase InuA (56 kDa, pI 3) and exoinulinase Inu1 (60 kDa, pI 4.3) were purified to homogeneity from the enzymatic complexes of P. canescens new transformants. The properties, such as substrate specificity, pH- and T-optima of activity, stability at different temperatures, influence of cations and anions on the catalytic activity, etc., of both recombinant inulinases were studied.

Isolation and characterization of extracellular pectin lyase from Penicillium canescens

Pectin lyase A (molecular weight 38 kD by SDS-PAGE, pI 6.7) was purified to homogeneity from culture broth of the mycelial fungus Penicillium canescens using chromatographic techniques. During genomic library screening, the gene encoding pectin lyase A from P. canescens (pelA) was isolated and sequenced, and the amino acid sequence was generated by applying the multiple alignment procedure (360 residues). A theoretical model for the three dimensional structure of the protein molecule was also proposed. Different properties of pectin lyase A were investigated: substrate specificity, pH- and temperature optimum of activity, stability under different pH and temperature conditions, and the effect of Ca2+ on enzyme activity. In the course of the laboratory trials, it was demonstrated that pectin lyase A from P. canescens could be successfully applied to production and clarification of juice.

[Use of a preparation from fungal pectin lyase in the food industry]

A new enzyme preparation of fungal pectin lyase (EC 4.2.2.10) was shown to be useful for the production of cranberry juice and clarification of apple juice in the food industry. A comparative study showed that the preparation of pectin lyase is competitive with commercial pectinase products. The molecular weight of homogeneous pectin lyase was 38 kDa. Properties of the homogeneous enzyme were studied. This enzyme was most efficient in removing highly esterified pectin.

[Properties of hemicellulases of the enzyme complex from Trichoderma longibrachiatum]

Six xylan-hydrolyzing enzymes have been isolated from the preparations Celloviridin G20x and Xybeten-Xyl, obtained previously based on the strain Trichoderma longibrachiatum (Trichoderma reesei) TW-1. The enzymes isolated were represented by three xylanases (XYLs), XYL I (20 kDa, pi 5.5), XYL II (21 kDa, pI 9.5), XYL III (30 kDa, pI 9.1); endoglucanase I (EG I), an enzyme exhibiting xylanase activity (57 kDa, pI 4.6); and two exodepolymerases, beta-xylosidase (beta-XYL; 80 kDa, pI 4.5) and alpha-L-arabinofuranosidase I (alpha-L-AF I; 55 kDa, pI 7.4). The substrate specificity of the enzymes isolated was determined. XYL II exhibited maximum specific xylanase activity (190 U/mg). The content of the enzymes in the preparation was assessed. Maximum contributions to the total xylanase activities of the preparations Celloviridin G20x and Xy-beten-Xyl were made by EG I and XYL II, respectively. Effects of temperature and pH on the enzyme activities, their stabilities under various conditions, and the kinetics of exhaustive hydrolysis of glucuronoxylan and arabinoxylan were studied. Combinations of endodepolymerases (XYL I, XYL II, XYL III, or EG I) and exodepolymerases (alpha-L-AF I or beta-XYL) produced synergistic effects on arabinoxylan cleavage. The reverse was the case when endodepolymerases, such as XYL I or EG I, were combined with alpha-L-AF I.

[New cellulases efficiently hydrolyzing lignocellulose pulp]

Commercial and pilot enzyme preparations from fungi of the genera Penicillium and Trichoderma have been compared with regard to their action on conifer wood pretreated with acidified aqueous ethanol (organosolve). In most experiments, enzymes from the genus Penicillium allowed higher yields of reducing sugars and glucose than those from Trichoderma. High beta-glucosidase activity is essential for deep pulp hydrolysis.

New effective method for analysis of the component composition of enzyme complexes from Trichoderma reesei

A method for analysis of the component composition of multienzyme complexes secreted by the filamentous fungus Trichoderma reesei was developed. The method is based on chromatofocusing followed by further identification of protein fractions according to their substrate specificity and molecular characteristics of the proteins. The method allows identifying practically all known cellulases and hemicellulases of T. reesei: endoglucanase I (EG I), EG II, EG III, cellobiohydrolase I (CBH I), CBH II, xylanase I (XYL I), XYL II, beta-xylosidase, alpha-L-arabinofuranosidase, acetyl xylan esterase, mannanase, alpha-galactosidase, xyloglucanase, polygalacturonase, and exo-beta-1,3-glucosidase. The component composition of several laboratory and commercial T. reesei preparations was studied and the content of the individual enzymes in these preparations was quantified. The influence of fermentation conditions on the component composition of secreted enzyme complexes was revealed. The characteristic features of enzyme preparations obtained in "cellulase" and "xylanase" fermentation conditions are shown.

[Studies of hydrolytic activity of enzyme preparations of Penicillium and Trychoderma fungi]

Enzyme preparations were isolated from the culture liquid of five mutant strains of the cellulase producer Penicillium verruculosum. The hydrolytic activities of these preparations against unbleached eucalypt cellulose was compared to that of commercial preparations of Trichoderma reesei (T. longibrachiatum). In the majority of cases, P. verruculosum enzymes provided higher yields of reducing sugars (RSs) and glucose. A correlation was found between the yield of RSs and the avicelase activity of the preparations in the reaction mixture.

Recombinant endo-beta-1,4-xylanase from Penicillium canescens

Recombinant endo-beta-1,4-xylanase (Xyl-31rec, 31 kD, pI 8.2-9.3, the tenth family of glycosyl hydrolases) was isolated from the culture liquid of Penicillium canescens (strain with the amplified homologous xylanase gene) by chromatofocusing on Mono P and hydrophobic chromatography on phenyl-Superose. It is shown that the biochemical and kinetic parameters, substrate specificity, stability, and other properties of the recombinant and native enzymes are almost the same. It was found that Xyl-31rec can be used for biobleaching of cellulose, the recombinant P. canescens strains providing a high yield of extracellular Xyl-31rec (up to 800-900 U/ml of culture liquid) and not secreting cellulases.

Cellulase Complex of the Fungus Chrysosporium lucknowense: Isolation and Characterization of Endoglucanases and Cellobiohydrolases

Using different chromatographic techniques, eight cellulolytic enzymes were isolated from the culture broth of a mutant strain of Chrysosporium lucknowense: six endoglucanases (EG: 25 kD, pI 4.0; 28 kD, pI 5.7; 44 kD, pI 6.0; 47 kD, pI 5.7; 51 kD, pI 4.8; 60 kD, pI 3.7) and two cellobiohydrolases (CBH I, 65 kD, pI 4.5; CBH II, 42 kD, pI 4.2). Some of the isolated cellulases were classified into known families of glycoside hydrolases: Cel6A (CBH II), Cel7A (CBH I), Cel12A (EG28), Cel45A (EG25). It was shown that EG44 and EG51 are two different forms of one enzyme. EG44 seems to be a catalytic module of an intact EG51 without a cellulose-binding module. All the enzymes had pH optimum of activity in the acidic range (at pH 4.5-6.0), whereas EG25 and EG47 retained 55-60% of the maximum activity at pH 8.5. Substrate specificity of the purified cellulases against carboxymethylcellulose (CMC), beta-glucan, Avicel, xylan, xyloglucan, laminarin, and p-nitrophenyl-beta-D-cellobioside was studied. EG44 and EG51 were characterized by the highest CMCase activity (59 and 52 U/mg protein). EG28 had the lowest CMCase activity (11 U/mg) amongst the endoglucanases; however, this enzyme displayed the highest activity against beta-glucan (125 U/mg). Only EG51 and CBH I were characterized by high adsorption ability on Avicel cellulose (98-99%). Kinetics of Avicel hydrolysis by the isolated cellulases in the presence of purified beta-glucosidase from Aspergillus japonicus was studied. The hydrolytic efficiency of cellulases (estimated as glucose yield after a 7-day reaction) decreased in the following order: CBH I, EG60, CBH II, EG51, EG47, EG25, EG28, EG44.

Isolation and Properties of Major Components of Penicillium canescens Extracellular Enzyme Complex

The composition of the enzyme complex secreted by Penicillium canescens was investigated. A scheme for purification of the main components of the complex by chromatofocusing on a Mono P column was developed. It was found that along with beta-galactosidase, the major components of the complex were endo-beta-1,4-xylanase (31 kD, pI 8.2-9.3), alpha-L-arabinofuranosidase (60 kD, pI 7.6), arabinoxylan-arabinofuranohydrolase (70 kD, pI 3.8-4.0), and endo-beta-1,3/1,4-glucanase (40 kD, pI 4.4). The substrate specificity, pH and temperature activity optima, adsorbability, thermal stability, and ability for synergic interaction of the isolated enzymes were studied.

Isolation and properties of pectinases from the fungus Aspergillus japonicus

Using anion-exchange chromatography on different carriers and phenyl-Sepharose hydrophobic chromatography, five pectolytic enzymes were isolated from the culture liquid of a mutant strain of Aspergillus japonicus: two endo-polygalacturonases (I and II, 38 and 65 kD, pI 5.6 and 3.3), pectin lyase (50 kD, pI 3.8), and two pectinesterases (I and II) with similar molecular weights (46 and 47 kD) and the same pI (3.8). The pectinesterases apparently represent two isoforms of the same enzyme. All purified enzymes were homogenous according to SDS-PAGE and polyacrylamide gel-IEF, except for endo-polygalacturonase II that gave two bands on isoelectric focusing, but one band on electrophoresis. All enzymes had maximal activity in an acid medium (at pH 4.0-5.5). The pectin lyase and pectinesterase were stable at 40-50 degrees C. The thermal stability of both endo-polygalacturonases was much lower (after 3 h of incubation at 30 degrees C, endo-polygalacturonases I and II lost 40 and 10% of the activity, respectively). The activity of endo-polygalacturonases I and II towards polygalacturonic acid strongly depended on NaCl concentration (optimal concentration of the salt was 0.1-0.2 M); the enzymes were also capable of reducing the viscosity of pectin solution, but rather slowly. The pectin lyase had no activity towards polygalacturonic acid. The activity of the pectin lyase increased with increasing degree of methylation of pectins. Both endo-polygalacturonases demonstrated synergism with the pectinesterase during the hydrolysis of highly methylated pectin. On the contrary, in the mixture of pectin lyase and pectinesterase an antagonism between the two enzymes was observed.

Viscometric method for assaying of total endodepolymerase activity of pectinases

An improved method for assaying of the total endodepolymerase activity of pectinases has been developed. The method is based on the determination of the viscosity of a citrus pectin solution in the presence of the enzyme using an Ostwald viscometer. The depolymerizing activity of different pectinases can be detected including polygalacturonase, polymethylgalacturonase, pectin lyase, and pectate lyase. One unit of the endodepolymerase activity corresponds to the activity resulting in 50% decrease in the relative viscosity of 0.5% citrus pectin solution for 5 min at 40 degrees C and the appropriate pH. Depending on the pH-optima of the enzymes, two modifications of the method are described: 1) for acid pectinases at pH 5.0, and 2) for neutral (mildly alkaline) pectinases at pH 8.0. The modifications differed in the control and in the calculation of the activity. Six enzyme preparations were used to demonstrate the applicability of the method. The parameter used for the calculation of the enzymatic activity was directly proportional to the enzyme concentration (the dependence was linear in the range of at least 10-fold change in the enzyme concentration). The relative error of the method did not exceed 10%.

[Isolation and properties of cellobiase from Penicillium verruculosum]

Cellobiase (beta-D-glucosidase) with a molecular weight of 100 kDa and pI 5.2 was isolated from the cellulolytic system of Penicillium verruculosum. Kinetic parameters of enzymatic hydrolysis of cellobiose, gentiobiose, sophorose, and synthetic substrates, i.e. methylumbelliferyl and p-nitrophenyl sugar derivatives were determined. Glucose and D-glucose-delta-lactone competitively inhibited cellobiase (Ki = 0.19 mM and 17 microM, respectively). Glucosyl transfer reactions were studied with cellobiose as a single substrate and in the mixture of cellobiose and methylumbelliferyl cellobioside. The product composition was determined in these systems. The ratio of hydrolysis and transfer reaction rates for cellobiose conversion was calculated.

Application of microassays for investigation of cellulase abrasive activity and backstaining

Model microassays were used for testing the denim-washing performance and indigo backstaining for Trichoderma reesei and Chrysosporium lucknowense commercial cellulase preparations on a 'test-tube scale'. C. lucknowense preparation demonstrated a higher potential in the denim biostoning process. The performance of four purified cellulases (two endoglucanases and two cellobiohydrolases) from C. lucknowense on cotton textiles was assayed, and the key enzyme (endoglucanase with a molecular weight of 25 kDa) responsible for high abrasion effects on denim fabrics was found.

Study of protein adsorption on indigo particles confirms the existence of enzyme--indigo interaction sites in cellulase molecules

Adsorption of several crude and purified cellulases (from Trichoderma reesei, Penicillium verruculosum and Chrysosporium lucknowense) on indigo particles and Avicel cellulose was studied. Much higher amounts of protein were bound to indigo than to cellulose under similar conditions. For different purified enzymes, the quantity of bound protein per mg of adsorbent (indigo or cellulose) varied in the range of 57-111 and 0-62 microg x mg(-1), respectively. However, in general, the enzyme adsorption on indigo was less specific than the adsorption on cellulose. Three endoglucanases, having the highest indigo-binding ability, demonstrated the best washing performance in the process of enzymatic denim treatment. These data confirmed our previous findings that certain cellulases, which have indigo-binding sites (clusters of closely located aromatic and other non-polar residues) on the surface of their molecules, may remove indigo from the denim fabric better than cellulases with lower content of hydrophobic residues exposed to solvent.

Electrochemical assay of endo-depolymerase activity of cellulases

A method for determination of endo-1,4-beta-D-glucanase activity of cellulase samples based on the indirect measurement of decrease in viscosity of a carboxymethylcellulose solution in an electrochemical cell in the presence of an electron carrier was developed. A rotating disk electrode is used as the working electrode. When two reactions (enzymatic and electrochemical) proceeded in the cell simultaneously, the limiting diffusion current at a constant applied potential increases as the viscosity of the solution decreases. Conditions where the initial rate of change of diffusion current (dI/dt) is proportional to the enzyme concentration were found. A good correlation between the new method and a previously known viscometric method for determination of endoglucanase activity was observed.

Transglycosylation activity of cellobiohydrolase I from Trichoderma longibrachiatum on synthetic and natural substrates

Using 4-methylumbelliferyl (MUF) beta-D-cellobioside as a substrate, the ability of cellobiohydrolase I from Trichoderma longibrachiatum to catalyze transglycosylation has been demonstrated. At substrate concentrations greater than 2 mM, the formation of MUF-tetrasaccharide was detected using HPLC. In the course of enzymatic reaction, a concentration of the transglycosylation product passed through a maximum, since at later stages of the reaction the product was further hydrolyzed. At MUF-beta-D-cellobioside concentrations of 2-10 mM, the maximum weight content of MUF-tetrasaccharide amounted to 1-4% of the total content of saccharides. In the reaction system, containing 2.5 mM MUF-beta-D-cellobioside and 10 mM MUF-beta-D-glucoside, MUF-trisaccharide was formed as the main transglycosylation product. In hydrolysis of natural substrates (cellulose and cellotriose) in the presence of MUF-beta-D-glucoside a formation of MUF-trisaccharide was also observed.

[Enzymatic hydrolysis of cellulose. Inactivation and stabilization of the enzymes of the cellulose complex]

The thermal inactivation of the individual cellulolytic components (endoglucanase, EC 3.2.1.4; exoglucosidase, EC 3.2.1.74; cellobiase, EC 3.2.1.21) from the fungi Trichoderma reesei, T. viride, T. lignorum an Aspergillus foetidus has been studied without resolution of the cellulase complexes. The kinetics of the thermal inactivation follow the first order for cellobiase of Asp. foetidus alone and show a more complex picture which is typical for a number of isoenzymes of different thermal stabilities for other cellulolytic components of all the cellulases under study. It was shown that selective elimination of acid proteinase from the cellulase preparations by affinity chromatography did not affect the time course of the thermal inactivation. Covalent attachment of the cellulases to porous glass and to some soluble high polymer supports only resulted in slight stabilizing effects (200-250%). Some polymer effectors (e. g. polyethylene glycols with Mr of 4000 and 40,000 and maltodextrins), as well as the end products of enzymatic hydrolysis of cellulose (i. e. glucose) did not affect the thermal stability of the cellulases under study. In some cases cellulose itself (cotton, CM-cellulose) produced a thermostabilizing effect (3-4-fold) on cellulolytic enzymes.