Purification and characterization of a β-1,4-glucosidase from a newly isolated strain of Fomitopsis pinicola

Fomitopsis meliae CFA 2, a novel brown rot for endoglucanase: emphasis towards enhanced endoglucanase production by statistical approach

Brown rot basidiomycetes are a principal group of wood-decaying fungi which degrade wood cellulose and hemicellulose by the combination of carbohydrate active enzymes and non-enzymatic oxidation reactions. Very scant information is available on carbohydrate active enzymes of brown rot fungi. In this context, present study focused on the production of cellulolytic–hemicellulolytic enzymes from newly isolated brown rot Fomitopsis meliae CFA 2. Under solid-state fermentation using wheat bran as the substrate Fomitopsis meliae CFA 2 was able to produce a maximum of 1391.12 ± 21.13 U/g of endoglucanase along with other cellulolytic and hemicellulolytic enzymes. Various fermentation parameters were optimised for enhanced production of endoglucanase by employing Plackett-Burman design followed by Box-Behnken design. A well-fitted regression equation with R² value of 98.91% was attained for endoglucanase. The yield of endoglucanase was enhanced by 1.83-fold after executing statistical optimisation of various fermentative parameters. The newly isolated Fomitopsis meliae CFA 2 was found to be a potential producer of endoglucanase. Enzymatic saccharification of alkali-treated wheat straw and rice straw resulted in release of 190.8 and 318.8 mg/g of reducing sugars, respectively.

Modeling of enzymatic activity of free β-glucosidase from palm weevil, Rhynchophorus palmarum Linn. (Coleoptera: Curculionidae) larvae: Effects of pH and temperature

Palm weevil, Rhynchophorus palmarum L., is an important pest of palm trees (Elaeis guineensis) around the tropical regions. Characterization of their digestive enzymes could be an important stage to develop appropriate pest control strategies. Study of these enzymes could also be of interest in different biotechnological applications. Among digestive enzymes, there is β-glucosidase which hydrolytically catalyzes the β-glycosidic linkage of glycosides. In the present work, the catalytic activity of β-glucosidase in the digestive juice of last larval instar of R. palmarum L. (Rpbgl) has been investigated using p-nitrophenyl-β-D-glucopyranoside (pNPG) as substrate. The "classical" physico-chemical properties for purified Rpbgl have been determined by the help of enzymatic activity modeling. Thus, the values of (325.4 ± 0.2) K, 5.28 ± 0.07 and (37.9 ± 0.6) kJ mol^-1 were obtained for optimum temperature, optimum pH and activation energy, respectively. The pK values for enzyme-substrate complex are 4.25 ± 0.07 and 6.20 ± 0.07 for nucleophile and the proton donor, respectively. Enzyme kinetics study was also performed and the values of (127 ± 6) U mg^-1 and (0.78 ± 0.08) mM were obtained for V_max and K_m, respectively. Using the Equilibrium model (EM), the thermal inactivation data were analyzed. ΔH_eq, T_eq, ΔG_inact^∗ and ΔG_cat^∗ were found to be (222 ± 4) kJ mol^-1, (323.0 ± 0.1) K, (101.9 ± 0.2) kJ mol^-1 and (53.37 ± 0.02) kJ mol^-1, respectively. These results show that Rpbgl is less stable with a narrow temperature tolerance compared to other β-glucosidases.

Production, immobilization and characterization of beta-glucosidase for application in cellulose degradation from a novel Aspergillus versicolor

Beta-glucosidase (EC 3.2.1.21) catalyzes the hydrolysis of cellobiose and cellooligosaccharides containing (1 → 4)-beta-glycosidic bonds to glucose, which is crucial in cellulosic ethanol production. In this study, Aspergillus versicolor, a novel highly productive beta-glucosidase strain, was first isolated from Camptotheca acuminata seeds. The highest beta-glucosidase activity with 812.86 U/mL was obtained by using the response surface methodology, and a 14.4-fold has increased compared to the control. The beta-glucosidase was then purified to homogeneity with recovery yield and specific activity of 25.98% and 499.15 U/mg, respectively. To enhance its stability and recyclability, the purified beta-glucosidase was first immobilized onto magnetic MnO₂ by electrostatic adsorption. The immobilized materials were characterized by FR-IT, TEM and FE-SEM. Compared with the free beta-glucosidase, the immobilized enzyme exhibited enhanced thermal stability (1.5-fold raise in half-life at 50 °C), and reusability (holding over 60% activity after eight cycles), besides, the optimum pH has increased to 6.0. Substrate specificity research suggested that the enzyme had high hydrolytic activity on cellobiose. It also had a hydrolysis effect on (1 → 3) and (1 → 6)-beta-glycosidic linkages. Application trials in cellulose hydrolysis revealed that the immobilized enzyme was comparatively more effective. Our results suggested this novel immobilized beta-glucosidase makes a promising alternative for the cellulosic ethanol production.

One-step purification of two novel thermotolerant β-1,4-glucosidases from a newly isolated strain of Fusarium chlamydosporum HML278 and their characterization

A newly identified cellulase-producing Fusarium chlamydosporum HML278 was cultivated under solid-state fermentation of sugarcane bagasse, and two new β-glucosides enzymes (BG FH1, BG FH2) were recovered from fermentation solution by modified non-denaturing active gel electrophoresis and gel filtration chromatography. SDS-PAGE analysis showed that the molecular weight of BG FH1 and BG FH2 was 93 kDa and 52 kDa, respectively, and the enzyme activity was 5.6 U/mg and 11.5 U/mg, respectively. The optimal reaction temperature of the enzymes was 60 ℃, and the enzymes were stable with a temperature lower than 70 ℃. The optimal pH of the purified enzymes was 6.0, and the enzymes were stable between pH 4–10. K_m and V_max values ​​were 2.76 mg/mL and 20.6 U/mg for pNPG, respectively. Thin-layer chromatography and high-performance liquid chromatography analysis showed that BG FH1and BG FH2 had hydrolysis activity toward cellobiose and could hydrolyze cellobiose into glucose. In addition, both enzymes exhibited transglycoside activity, which could use glucose to synthesize cellobiose and cellotriose, and preferentially synthesize alcohol. In conclusion, our study demonstrated that F. chlamydosporum HML278 produces heat-resistant β-glucosidases with both hydrolytic activity and transglycosidic activity, and these β-glucosidases have potential application in bioethanol and papermaking industries.

β-Glucosidase BGL1 from Coprinopsis cinerea Exhibits a Distinctive Hydrolysis and Transglycosylation Activity for Application in the Production of 3-O-β-d-Gentiobiosyl-d-laminarioligosaccharides

We previously reported that β-glucosidase BGL1 at low concentration (15 μg mL^-1) from Coprinopsis cinerea exhibited hydrolytic activity only toward laminarioligosaccharides but not toward cellooligosaccharides and gentiobiose. This study shows that BGL1 at high concentration (200 μg mL^-1) also hydrolyzed cellobiose and gentiobiose, which accounted for only 0.83 and 2.05% of its activity toward laminaribiose, respectively. Interestingly, BGL1 at low concentration (1.5 μg mL^-1) showed transglycosylation but BGL1 at high concentration (200 μg mL^-1) did not. BGL1 utilizes only laminarioligosaccharides but not glucose, gentiobiose, and cellobiose to synthesize the higher oligosaccharides. BGL1 transferred one glucosyl residue from substrate laminarioligosaccharide to another laminarioligosaccharide as an acceptor in a β(1 → 3) or β(1 → 6) fashion to produce higher laminarioligosaccharides or 3-O-β-d-gentiobiosyl-d-laminarioligosaccharides. The BGL1-digested laminaritriose exhibited approximately 90% enhancement in the anti-oxidant activity compared to that of untreated laminaritriose, implying a potential application of BGL1-based transglycosylation for the production of high value-added rare oligosaccharides.

Cloning, purification, and characterization of GH3 β-glucosidase, MtBgl85, from Microbulbifer thermotolerans DAU221

Background

β-Glucosidases have attracted considerable attention due to their important roles in various biotechnological processes such as cellulose degradation to make energy and hydrolysis of isoflavone. Microbulbifer thermotolerans (M. thermotolerans) is isolated from deep-sea sediment and has not been researched much yet. As a potential candidate for a variety of biotechnological industries, β-glucosidases from the novel bacterial species should be researched extensively.

Methods

β-Glucosidase, MtBgl85, from M. thermotolerans DAU221 was purified by His-tag affinity chromatography and confirmed by SDS-PAGE and zymogram. Its biochemical and physiological properties, such as effects of temperature, pH, metal ions, and organic solvents, substrate specificity, and isoflavone hydrolysis, were investigated.

Results

M. thermotolerans DAU221 showed β-glucosidase activity in a marine broth plate containing 0.1% esculin and 0.25% ammonium iron (III) citrate. The β-glucosidase gene, mtbgl85, was isolated from the whole genome sequence of M. thermotolerans DAU221. The β-glucosidase gene was 2,319 bp and encoded 772 amino acids. The deduced amino acid sequence had a 43% identity with OaBGL84 from Olleya aquimaris and 35% and 32% identity with to CfBgl3A and CfBgl3C from Cellulomonas fimi among bacterial glycosyl hydrolase family 3, respectively. The optimal temperature of MtBgl85 was 50 °C and the optimum pH was 7.0. MtBgl85 activity was strongly reduced in the presence of Hg²⁺ and Cu²⁺ ions. As a result of measuring the activity at various concentrations of NaCl, it was confirmed that the activity was maintained up to the concentration of 1 M, but gradually decreased with increasing concentration. MtBgl85 showed higher enzyme stability at non-polar solvents (high Log P_ow) than polar solvents (low Log P_ow). The hydrolyzed products of isoflavone glycosides and arbutin were analyzed by HPLC.

Novel Ethanol- and 5-Hydroxymethyl Furfural-Stimulated β-Glucosidase Retrieved From a Brazilian Secondary Atlantic Forest Soil Metagenome

Beta-glucosidases are key enzymes involved in lignocellulosic biomass degradation for bioethanol production, which complete the final step during cellulose hydrolysis by converting cellobiose into glucose. Currently, industry requires enzymes with improved catalytic performance or tolerance to process-specific parameters. In this sense, metagenomics has become a powerful tool for accessing and exploring the biochemical biodiversity present in different natural environments. Here, we report the identification of a novel β-glucosidase from metagenomic DNA isolated from soil samples enriched with decaying plant matter from a Secondary Atlantic Forest region. For this, we employed a functional screening approach using an optimized and synthetic broad host-range vector for library production. The novel β-glucosidase – named Lfa2 – displays three GH3-family conserved domains and conserved catalytic amino acids D283 and E487. The purified enzyme was most active in pH 5.5 and at 50°C, and showed hydrolytic activity toward several pNP synthetic substrates containing β-glucose, β-galactose, β-xylose, β-fucose, and α-arabinopyranose, as well as toward cellobiose. Lfa2 showed considerable glucose tolerance, exhibiting an IC₅₀ of 300 mM glucose and 30% of remaining activity in 600 mM glucose. In addition, Lfa2 retained full or slightly enhanced activity in the presence of several metal ions. Further, β-glucosidase activity was increased by 1.7-fold in the presence of 10% (v/v) ethanol, a concentration that can be reached in conventional fermentation processes. Similarly, Lfa2 showed 1.7-fold enhanced activity at high concentrations of 5-hydroxymethyl furfural, one of the most important cellulase inhibitors in pretreated sugarcane bagasse hydrolysates. Moreover, the synergistic effect of Lfa2 on Bacillus subtilis GH5-CBM3 endoglucanase activity was demonstrated by the increased production of glucose (1.6-fold). Together, these results indicate that β-glucosidase Lfa2 is a promissory enzyme candidate for utilization in diverse industrial applications, such as cellulosic biomass degradation or flavor enhancement in winemaking and grape processing.

Expression and characterization of a glucose-tolerant β-1,4-glucosidase with wide substrate specificity from Cytophaga hutchinsonii

Cytophaga hutchinsonii is a gram-negative bacterium that can efficiently degrade crystalline cellulose by a novel strategy without cell-free cellulases or cellulosomes. Genomic analysis implied that C. hutchinsonii had endoglucanases and β-glucosidases but no exoglucanases which could processively digest cellulose and produce cellobiose. In this study, BglA was functionally expressed in Escherichia coli and found to be a β-glucosidase with wide substrate specificity. It can hydrolyze pNPG, pNPC, cellobiose, and cellodextrins. Moreover, unlike most β-glucosidases whose activity greatly decreases with increasing length of the substrate chains, BglA has similar activity on cellobiose and larger cellodextrins. The K _m values of BglA on cellobiose, cellotriose, and cellotetraose were calculated to be 4.8 × 10^-2, 5.6 × 10^-2, and 5.3 × 10^-2 mol/l, respectively. These properties give BglA a great advantage to cooperate with endoglucanases in C. hutchinsonii in cellulose degradation. We proposed that C. hutchinsonii could utilize a simple cellulase system which consists of endoglucanases and β-glucosidases to completely digest amorphous cellulose into glucose. Moreover, BglA was also found to be highly tolerant to glucose as it retained 40 % activity when the concentration of glucose was 100 times higher than that of the substrate, showing potential application in the bioenergy industry.

A multifunctional thermophilic glycoside hydrolase from Caldicellulosiruptor owensensis with potential applications in production of biofuels and biochemicals

BACKGROUND

Thermophilic enzymes have attracted much attention for their advantages of high reaction velocity, exceptional thermostability, and decreased risk of contamination. Exploring efficient thermophilic glycoside hydrolases will accelerate the industrialization of biofuels and biochemicals.

RESULTS

A multifunctional glycoside hydrolase (GH) CoGH1A, belonging to GH1 family with high activities of β-d-glucosidase, exoglucanase, β-d-xylosidase, β-d-galactosidase, and transgalactosylation, was cloned and expressed from the extremely thermophilic bacterium Caldicellulosiruptor owensensis. The enzyme exerts excellent thermostability by retaining 100 % activity after 12-h incubation at 75 °C. The catalytic coefficients (k cat/K m) of the enzyme against pNP-β-D-galactopyranoside, pNP-β-D-glucopyranoside, pNP-β-D-cellobioside, pNP-β-D-xylopyranoside, and cellobiose were, respectively, 7450.0, 2467.5, 1085.4, 90.9, and 137.3 mM(-1) s(-1). When CoGH1A was supplemented at the dosage of 20 Ucellobiose g(-1) biomass for hydrolysis of the pretreated corn stover, comparing with the control, the glucose and xylose yields were, respectively, increased 37.9 and 42.1 %, indicating that the enzyme contributed not only for glucose but also for xylose release. The efficiencies of lactose decomposition and synthesis of galactooligosaccharides (GalOS) by CoGH1A were investigated at low (40 g L(-1)) and high (500 g L(-1)) initial lactose concentrations. At low lactose concentration, the time for decomposition of 83 % lactose was 10 min, which is much shorter than the reported 2-10 h for reaching such a decomposition rate. At high lactose concentration, after 50-min catalysis, the GalOS concentration reached 221 g L(-1) with a productivity of 265.2 g L(-1) h(-1). This productivity is at least 12-fold higher than those reported in literature.

CONCLUSIONS

The multifunctional glycoside hydrolase CoGH1A has high capabilities in saccharification of lignocellulosic biomass, decomposition of lactose, and synthesis of galactooligosaccharides. It is a promising enzyme to be used for bioconversion of carbohydrates in industrial scale. In addition, the results of this study indicate that the extremely thermophilic bacteria are potential resources for screening highly efficient glycoside hydrolases for the production of biofuels and biochemicals.

Physicochemical properties of thermotolerant extracellular β-glucosidase from Talaromyces thermophilus and enzymatic synthesis of cello-oligosaccharides

A thermophilic fungus, Talaromyces thermophilus that produces a novel thermotolerant extra-cellular β-glucosidase (Bgl.tls), was isolated from Tunisian soil samples. The enzyme was purified from the culture filtrates of T. thermophilus grown on lactose using gel filtration, ion exchange chromatography and FPLC. The monomeric enzyme had a molecular mass of 116.0 kDa and a high specific activity of 1429 UI/mg. Bgl.tls exhibited optimal activity at pH 5.0 and 65 °C. It was also stable over a wide range of pH (4.0-10.0) and stable at 50 °C for 34 h. Bgl.tls retained about 80% of its initial activity after 1.0 hours of preincubation at 60 °C. The Km and Vmax values recorded for pNPG were 0.25 mM and 228.7 µmol min(-1), respectively. Bgl.tls was activated by Mn(2+), Mg(2+), Ca(2+) and Co(2+) but obviously inhibited by Fe(2+) and Cu(2+). It was able to hydrolyze a variety of aryl / alkyl -β-glucosides and disaccharides as well as (1 → 6) and (1 → 4)-β-glucosidic linkages and α-glycosidic substrates, thus providing evidence for its broad substrate specificity. The enzyme also displayed high hydrolytic and transglycosylation activities. Overall, this study is the first report on the purification and physicochemical properties of a β-glucosidase secreted by T. thermophilus. The cello-oligosaccharides synthesized by this enzyme within 2 h were mainly cellotriose, cellotetraose and cellopentaose identified by HPLC and ESI-MS techniques.

Heterologous Expression and Characterization of a GH3 β-Glucosidase from Thermophilic Fungi Myceliophthora thermophila in Pichia pastoris

A novel β-glucosidase of glycoside hydrolase (GH) family 3 from Myceliophthora thermophila (mtbgl3b) was successfully expressed in Pichia pastoris. The full-length gene consists of 2613 bp nucleotides encoding a protein of 870 amino acids. MtBgl3b showed maximum activity at pH 5.0 and remained more than 70 % relative activity at 3.5-6.0. The enzyme displayed the highest activity at 60 °C and kept about 90 % relative activity for 50-65 °C; besides, the enzyme showed psychrophilic trait and remains 51 % relative activity at 40 °C. MtBgl3b exhibited good stability over a wide pH range of 3.0-10.0 and was thermostable at 60 and 65 °C. The enzyme displayed highest activity towards p-nitrophenyl-β-D-glucopyranoside (pNPG), followed by p-nitrophenyl-D-cellobioside (pNPC), cellotetraose, cellotriose, cellobiose, and gentiobiose. When using 10 % cellobiose (w/v) as the substrate, the enzyme showed transglycosylation activity to produce the cellotriose. The kinetic parametric of K m and V max were 2.78 mM and 927.9 μM mg(-1) min(-1), respectively. Finally, the reaction mode of the enzyme and the substrates were analyzed by molecular docking approach.

Characterization of an acid-tolerant β-1,4-glucosidase from Fusarium oxysporum and its potential as an animal feed additive

An extracellular β-glucosidase (BGL) from Fusarium oxysporum was purified to homogeneity by a single chromatography step on a gel filtration column. The optimum activity of BGL on cellobiose was observed at pH 5.0 and 60 °C. Under the same conditions, the K(m) and V(max) values for p-nitrophenyl β-D-glucopyranoside and cellobiose were 2.53 mM, 268 U mg protein(-1) and 20.3 mM, 193 U mg protein(-1), respectively. The F. oxysporum BGL enzyme was highly stable at acidic pH (t 1/2 = 470 min at pH 3). A commercial BGL Novo188 (Novozymes) and F. oxysporum BGL were compared in their ability to supplement Celluclast 1.5 L (Novozymes). In comparison with the commercial Novo188 (267 mg g substrate(-1)), F. oxysporum BGL supplementation released more reducing sugars (330 mg g substrate(-1)) from cellulose under simulated gastric conditions. These properties make F. oxysporum BGL a good candidate as a new commercial BGL to improve the nutrient bioavailability of animal feed.

Biochemical properties of a novel glycoside hydrolase family 1 β-glucosidase (PtBglu1) from Paecilomyces thermophila expressed in Pichia pastoris

A novel β-glucosidase gene (PtBglu1) from the thermophilic fungus, Paecilomyces thermophila, was cloned and expressed in Pichia pastoris. PtBglu1 contained an open reading frame of 1440-bp nucleotides and encoded a protein of 479 amino acids which showed significant similarity to other fungal β-glucosidases from glycoside hydrolase (GH) family 1. The recombinant β-glucosidase (PtBglu1) was secreted at high level of 190.2 U mL(-1) in high cell density fermentor (5L). PtBglu1 was purified to homogeneity, and was found to be a glycoprotein with molecular mass of 56.7 kDa. The purified PtBglu1 showed optimum catalytic activity at pH 6.0 and 55 °C. The enzyme exhibited broad substrate specificity with highest activity toward pNP-β-D-glucopyranoside, followed by pNP-β-D-galactopyranoside and cellobiose. The K(m) values for pNP-β-D-glucopyranoside, cellobiose, gentiobiose and salicin were 0.55 mM, 1.0 mM, 1.74 mM and 6.85 mM, respectively. These properties make PtBglu1 a potential candidate for various industrial applications.

Identifying and characterizing the most significant β-glucosidase of the novel species Aspergillus saccharolyticus

The newly discovered fungal species Aspergillus saccharolyticus was found to produce a culture broth rich in β-glucosidase activity. In this present work, the main β-glucosidase of A. saccharolyticus responsible for the efficient hydrolytic activity was identified, isolated, and characterized. Ion exchange chromatography was used to fractionate the culture broth, yielding fractions with high β-glucosidase activity and only 1 visible band on an SDS–PAGE gel. Mass spectrometry analysis of this band gave peptide matches to β-glucosidases from aspergilli. Through a polymerase chain reaction approach using degenerate primers and genome walking, a 2919 bp sequence encoding the 860 amino acid BGL1 polypeptide was determined. BGL1 of A. saccharolyticus has 91% and 82% identity with BGL1 from Aspergillus aculeatus and BGL1 from Aspergillus niger , respectively, both belonging to Glycoside Hydrolase family 3. Homology modeling studies suggested β-glucosidase activity with preserved retaining mechanism and a wider catalytic pocket compared with other β-glucosidases. The bgl1 gene was heterologously expressed in Trichoderma reesei QM6a, purified, and characterized by enzyme kinetics studies. The enzyme can hydrolyze cellobiose, p-nitrophenyl-β-d-glucoside, and cellodextrins. The enzyme showed good thermostability, was stable at 50 °C, and at 60 °C it had a half-life of approximately 6 h.

Saccharification of woody biomass using glycoside hydrolases from Stereum hirsutum

Enzymatic saccharification of woody biomasses was performed using glycoside hydrolases from Stereum hirsutum, a newly isolated fungal strain found to secrete efficient glycoside hydrolases. The strain showed the highest β-glucosidase, cellobiohydrolase, endoglucanase, endoxylanase, laccase, and filter paper activity of 10.3, 1.7, 10.3, 29.9, 0.12, and 0.58 U/ml, respectively. Among the various biomasses tested for saccharification, pine biomass produced maximum reducing sugar. Response surface methodology was used to optimize the hydrolysis of pine biomass to achieve the highest level of sugars. The parameters including enzyme, substrate concentration, temperature and pH were found to be critical for the conversion of pine biomass into sugars. Maximum saccharification of 49.7% (435 mg/g-substrate) was obtained after 96 h of hydrolysis. A close agreement between the experimental results and the model predictions was achieved. S. hirsutum could be a good choice for the production of reducing sugars from cellulosic biomasses.

Hydrolysis of lignocellulosic feedstock by novel cellulases originating from Pseudomonas sp. CL3 for fermentative hydrogen production

A newly isolated indigenous bacterium Pseudomonas sp. CL3 was able to produce novel cellulases consisting of endo-β-1,4-d-glucanase (80 and 100 kDa), exo-β-1,4-d-glucanase (55 kDa) and β-1,4-d-glucosidase (65 kDa) characterized by enzyme assay and zymography analysis. In addition, the CL3 strain also produced xylanase with a molecular weight of 20 kDa. The optimal temperature for enzyme activity was 50, 45, 45 and 55 °C for endo-β-1,4-d-glucanase, exo-β-1,4-d-glucanase, β-1,4-d-glucosidase and xylanase, respectively. All the enzymes displayed optimal activity at pH 6.0. The cellulases/xylanase could hydrolyze cellulosic materials very effectively and were thus used to hydrolyze natural agricultural waste (i.e., bagasse) for clean energy (H2) production by Clostridium pasteurianum CH4 using separate hydrolysis and fermentation process. The maximum hydrogen production rate and cumulative hydrogen production were 35 ml/L/h and 1420 ml/L, respectively, with a hydrogen yield of around 0.96 mol H2/mol glucose.

Identification, cloning, and characterization of β-glucosidase from Ustilago esculenta

Hydrolytic enzymes responsible for laminarin degradation were found to be secreted during growth of Ustilago esculenta on laminarin. An enzyme involved in laminarin degradation was purified by assaying release of glucose from laminaribiose. Ion-exchange chromatography of the culture filtrate followed by size-exclusion chromatography yielded a 110-kDa protein associated with laminaribiose hydrolysis. LC/MS/MS analysis of the 110-kDa protein identified three peptide sequences that shared significant similarity with a putative glucoside hydrolase family (GH) 3 β-glucosidase in Ustilago maydis. Based on the DNA sequence of the U. maydis GH3 β-glucosidase, a gene encoding a putative GH3 β-glucosidase in U. esculenta (Uebgl3A) was cloned by PCR. Based on the deduced amino acid sequence, the protein encoded by Uebgl3A has a molecular mass of 91 kDa and shares 90% identity with U. maydis GH3 β-glucosidase. Recombinant UeBgl3A expressed in Aspergillus oryzae released glucose from β-1,3-, β-1,4-, and β-1,6-linked oligosaccharides, and from 1,3-1,4-β-glucan and laminarin polysaccharides, indicating that UeBgl3A is a β-glucosidase. Kinetic analysis showed that UeBgl3A preferentially hydrolyzed laminaritriose and laminaritetraose. These results suggest that UeBgl3A is a key enzyme that produces glucose from laminarioligosaccharides during growth of U. esculenta on laminarin.

Expression and characterization of a cold-active and xylose-stimulated β-glucosidase from Marinomonas MWYL1 in Escherichia coli

The gene encoding a cold-active and xylose-stimulated β-glucosidase of Marinomonas MWYL1 was synthesized and expressed in Escherichia coli. The recombinant enzyme (reBglM1) was purified and characterized. The molecular mass of the purified reBglM1 determined by SDS-PAGE agree with the calculated values (50.6 Da). Optima of temperature and pH for enzyme activity were 40 °C and 7.0, respectively. The enzyme exhibited about 20% activity at 5 °C and was stable over the range of pH 5.5-10.0. The presence of xylose significantly enhanced enzyme activity even at higher concentrations up to 600 mM, with maximal stimulatory effect (about 1.45-fold) around 300 mM. The enzyme is active with both glucosides and galactosides and showed high catalytic efficiency (k (cat) = 500.5 s(-1)) for oNPGlc. These characterizations enable the enzyme to be a promising candidate for industrial applications.

Identification and functional analysis of a gene encoding β-glucosidase from the brown-rot basidiomycete Fomitopsis palustris

The brown-rot basidiomycete Fomitopsis palustris is known to degrade crystalline cellulose (Avicel) and produce three major cellulases, exoglucanases, endoglucanases, and β-glucosidases. A novel β-glucosidase designated as Cel3A was identified from F. palustris grown at the expense of Avicel. The deduced amino acid sequence of Cel3A showed high homology with those of other fungal β-glucosidases that belong to glycosyl hydrolase (GH) family 3. The sequence analysis also indicated that Cel3A contains the N- and C-terminal domains of GH family 3 and Asp-209 was conserved as a catalytic nucleophile. The cloned gene was successfully expressed in the yeast Pichia pastoris and the recombinant protein exhibited β-glucosidase activity with cellobiose and some degree of thermostability. Considering the size and sequence of the protein, the β-glucosidase identified in this study is different from the protein purified directly from F. palustris in the previous study. Our results suggest that the fungus possesses at least two β-glucosidase genes.

Conversion of woody biomass into fermentable sugars by cellulase from Agaricus arvensis

Agaricus arvensis, a newly isolated basidiomycetous fungus, was found to secrete efficient cellulases. The strain produced the highest endoglucanase (EG), cellobiohydrolase (CBH) and beta-glucosidase (BGL) activities of 0.3, 3.2 and 8U/mg-protein, respectively, with rice straw as the carbon source. Saccharification of the woody biomass with A. arvensis cellulase as the enzyme source released a high level of fermentable sugars. Enzymatic hydrolysis of the poplar biomass was optimized using the response surface methodology in order to study the influence of the variables (pH, temperature, cellulases concentration and substrate concentration). The enzyme and substrate concentrations were identified as the limiting factors for the saccharification of poplar wood biomass. A total reducing sugar level of 29g/L (293mg/g-substrate) was obtained at an enzyme concentration of 65FPU/g-substrate after optimization of the hydrolysis parameters. The model validation showed a good agreement between the experimental results and the predicted responses. A. arvensis could be a good candidate for the production of reducing sugars from a cellulosic biomass.

A method of purification, identification and characterization of β-glucosidase from Trichoderma koningii AS3.2774

In this study, we used native gradient-polyacrylamide gel electrophoresis and electroelution (NGGEE) to purify enzymatic proteins from Trichoderma koningii AS3.2774. With this method, we purified eight enzymatic proteins and classified them to the cellulase system by comparing secretions of T. koningii in inductive medium and in repressive medium. It resulted in 24-fold β-glucosidase (BG) purification with a recovery rate of 5.5%, and a specific activity of 994.6IUmg(-1) protein. The final yield of BG reached 8μg under purifying procedure of NGGEE. We also identified BG using the enzyme assay with thin-layer chromatography and MALDI-TOFMS. This BG had one subunit with a molecular mass of 69.1kDa as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The hydrolytic activity of the BG had an optimal pH of 5.0, an optimal temperature of 50°C, an isoelectric point of 5.68 and a K(m) for p-nitrophenyl-β-d-glucopyranoside of 2.67mM. Taken together, we show that NGGEE is a reliable method through which μg grade of active proteins can be purified.