A highly-active endo-1,3-1,4-β-glucanase from thermophilic Talaromyces emersonii CBS394.64 with application potential in the brewing and feed industries

A 1245-bp endoglucanase gene of glycoside hydrolase (GH) family 7, egl7A, was cloned from the acidothermophilic fungus Talaromyces emersonii CBS394.64 and successfully expressed in Pichia pastoris. Sequence alignments indicated that Egl7A had highest identity of 62.7% at the amino acid level with the functionally characterized endoglucanase from Aspergillus terreus NIH2624. Purified recombinant Egl7A exhibited the maximum activity at pH 4.5 and 70 °C, retained stable over the pH range of 2.0–12.0 and at 65 °C, and was strongly resistant to acidic and neutral proteases, most metal ions and SDS. The enzyme exhibited the highest specific activity reported so far (11,299 U mg⁻¹) when using barley β-glucan as the substrate. Egl7A exhibited broad substrate specificity, including barley β-glucan, lichenin, CMC-Na, and xylan and had capacity to cleave cellopentaose and cellohexaose into smaller units rapidly. Under simulated mashing conditions, addition of Egl7A reduced the mash viscosity by 12.40%; when combined with a GH10 xylanase, more viscosity reduction (27.75%) was observed, which is significantly higher than that of the commercial enzyme Ultraflo XL (17.91%). All these properties make Egl7A attractive for potential applications in the feed and brewing industries.     

Comparison of the Heterologous Expression of Trichoderma reesei Endoglucanase II and Cellobiohydrolase II in the Yeasts Pichia pastoris and Yarrowia lipolytica

The sequences encoding the genes for endoglucanase II and cellobiohydrolase II from the fungus Trichoderma reesei QM9414 were successfully cloned and expressed in Yarrowia lipolytica under the control of the POX2 or TEF promoters, and using either the native or preproLip2 secretion signals. The expression level of both recombinant enzymes was compared with that obtained using Pichia pastoris, under the control of the AOX1 promoter to evaluate the utility of Y. lipolytica as a host strain for recombinant EGII and CBHII production. Extracellular endoglucanase activity was similar between TEF-preoproLip2-eglII expressed in Y. lipolytica and P. pastoris induced by 0.5 % (v/v) methanol, but when recombinant protein expression in P. pastoris was induced with 3 % (v/v) methanol, the activity was increased by about sevenfold. In contrast, the expression level of cellobiohydrolase from the TEF-preproLip2-cbhII cassette was higher in Y. lipolytica than in P. pastoris. Transformed Y. lipolytica produced up to 15 mg/l endoglucanase and 50 mg/l cellobiohydrolase, with the specific activity of both proteins being greater than their homologs produced by P. pastoris. Partial characterization of recombinant endoglucanase II and cellobiohydrolase II expressed in both yeasts revealed their optimum pH and temperature, and their pH and temperature stabilities were identical and hyperglycosylation had little effect on their enzymatic activity and properties.     

Cellulase production from Aspergillus niger MS82: effect of temperature and pH

Fungal cellulases are well-studied enzymes and are used in various industrial processes. Much of the knowledge of enzymatic depolymerization of cellulosic material has come from Trichoderma cellulase system. Species of Trichoderma can produce substantial amounts of endoglucanase and exoglucanase but very low levels of β-glucosidase. This deficiency necessitates screening of fungi for cellulytic potential. A number of indigenously isolated fungi were screened for cellulytic potential. In the present study, the kinetics of cellulase production from an indigenous strain of Aspergillus niger MS82 is reported. Product formation parameters of endoglucanase and β-glucosidase (Q_p + Y_p/s) indicate that A. niger MS82 is capable of producing moderate to high levels of both endoglucanase and β-glucosidase when grown on different carbon containing natural substrates, for example, grass, corncob, bagasse along side purified celluloses. Furthermore, it was observed that the production of endoglucanase reaches its maximum during exponential phase of growth, while β-glucosidase during the Stationary phase. Enzyme production by solid-state fermentation was also investigated and found to be promising. Highest production of cellulase was noted at pH 4.0 at 35 °C under submerged conditions. Growth and enzyme production was affected by variations in temperature and pH.     

Purification and properties of cellulase enzymes from Robillarda sp. Y-20

One endo-β-1,4-glucanase (EC 3.2.1.4) and two unique β-glucosidases (EC 3.2.1.21) have been isolated from culture filtrates Robillarda sp. Y-20 by combinations of DEAE A-50 column chromatography and isoelectric focusing. These enzymes were homogeneous on gel filtration, isoelectric focusing and polyacrylamide gel electrophoresis with and without sodium dodecyl sulphate (SDS). The molecular weights of endoglucanase, and the two β-glucosidases, I and II by SDS-polyacrylamide gel electrophoresis were 59000, 76000 and 54000, respectively. The pI values were 3.5, 7.5, and 3.8 for endoglucanase, β-glucosidase I and II, respectively. The major β-glucosidase I was a glycoprotein, but the endoglucanase and β-glucosidase II were not. The endoglucanase rapidly reduced the viscosity of carboxymethyl (CM) cellulose with concomitant production of reducing sugar. The enzyme had very low activity with crystalline cellulose such as insoluble acid treated cellulose, Avicel and filter paper. The endoglucanase attacked celloheptaose to cellotetraose more readily than cellotriose, but did not hydrolyze cellobiose. Both β-glucosidases attacked celloheptaose to cellotetraose more readily than cellotriose and cellobiose, but did not hydrolyze CM-cellulose and insoluble acid treated cellulose. Strong synergism was observed for hydrolysis of CM-cellulose by the endoglucanase and β-glucosidases.     

Hyperthermostable Endoglucanase from Pyrococcus horikoshii

An endoglucanase homolog from the hyperthermophilic archaeon Pyrococcus horikoshii was expressed in Escherichia coli, and its enzymatic characteristics were examined. The expressed protein was a hyperthermostable endoglucanase which hydrolyzes celluloses, including Avicel and carboxymethyl cellulose, as well as β-glucose oligomers. This enzyme is the first endoglucanase belonging to glycosidase family 5 found from Pyrococcus species and is also the first hyperthermostable endoglucanase to which celluloses are the best substrates. This enzyme is expected to be useful for industrial hydrolysis of cellulose at high temperatures, particularly in biopolishing of cotton products.     

Carbohydrate-hydrolyzing enzyme ratios during fungal degradation of woody and non-woody lignocellulose substrates

Understanding the order that enzymes are secreted during lignocellulosic degradation is relevant both to better understanding basic fungal degradation mechanisms and to industrial attempts to control reactions for biofuels production and other bioprocessing technology. Much is known about the enzymes that are produced and their effect on individual substrates, but little is known about temporal variation and relative enzyme activity on different lignocellulosics substrates. Wood decay fungi Trametes versicolor and Postia placenta were grown in liquid culture with different substrates (aspen, pine, corn stover, prairie grass and alfalfa) over a 16-week period. Samples of liquid media were taken every 2 weeks for endoglucanase, β-glucosidase and xylanase activity measurement. Endoglucanase:β-glucosidase:xylanase ratios varied for both fungi over the sampling period. T. versicolor showed large differences in cellulase enzyme (total cellulase:endoglucanase:β-glucosidase) composition when grown on woody substrates compared with non-woody substrates; there were also difference between the two wood types. This research presents evidence that the ratio of carbohydrate-hydrolyzing enzymes secreted by fungi is not influenced solely by lignin:carbohydrate content of the substrate and other factors including cell anatomy and constituent composition have some control on enzyme production. This provides a useful and broad survey of natural adaptations to various plant tissues relevant to bioenergy and general bioprospecting.     

Marine-derived Penicillium in Korea: diversity,enzyme activity,and antifungal properties

The diversity of marine-derived Penicillium from Korea was investigated using morphological and multigene phylogenetic approaches, analyzing sequences of the internal transcribed spacer region, β-tubulin gene, and RNA polymerase subunit II gene. In addition, the biological activity of all isolated strains was evaluated. We tested for the extracellular enzyme activity of alginase, endoglucanase, and β-glucosidase, and antifungal activity against two plant pathogens (Colletotrichum acutatum and Fusarium oxysporum). A total of 184 strains of 36 Penicillium species were isolated, with 27 species being identified. The most common species were Penicillium polonicum (19.6 %), P. rubens (11.4 %), P. chrysogenum (11.4 %), and P. crustosum (10.9 %). The diversity of Penicillium strains isolated from soil (foreshore soil and sand) and marine macroorganisms was higher than the diversity of strains isolated from seawater. While many of the isolated strains showed alginase and β-glucosidase activity, no endoglucanase activity was found. More than half the strains (50.5 %) showed antifungal activity against at least one of the plant pathogens tested. Compared with other strains in this study, P. citrinum (strain SFC20140101-M662) showed high antifungal activity against both plant pathogens. The results reported here expand our knowledge of marine-derived Penicillium diversity. The relatively high proportion of strains that showed antifungal and enzyme activity demonstrates that marine-derived Penicillium have great potential to be used in the production of natural bioactive products for pharmaceutical and/or industrial use.     

The unique GH5 cellulase member in the extreme halotolerant fungus Aspergillus glaucus CCHA is an endoglucanase with multiple tolerance to salt,alkali and heat: prospects for straw degradation applications

In a halotolerant fungus Aspergillus glaucus CCHA, several functional proteins with stress-tolerant activity have been studied, but no secretory enzymes have been identified yet. The unique GH5 cellulase candidate from A. glaucus, an endoglucanase termed as AgCMCase, was cloned, expressed in the Pichia pastoris system and the purified enzyme was characterized. A large amount of recombinant enzyme secreted by the P. pastoris GS115 strain was purified to homogeneity. The molecular weight of the purified endoglucanase is about 55.0 kDa. The AgCMCase exhibited optimum catalytic activity at pH 5.0 and 55 °C. However, it remained relatively stable at temperatures ranging from 45 to 80 °C and pH ranging from 4.0 to 9.0. In addition, it showed higher activity at extreme NaCl concentrations from 1.0 to 4.0 M, suggesting it is an enzyme highly stable under heat, acid, alkaline and saline conditions. To evaluate the catalytic activity of AgCMCase, the hydrolysis products of rice and corn straws were successfully studied. In conclusion, the AgCMCase is a thermostable and salt-tolerant cellulase with potential for industrial application.

     

An alkaline thermostable recombinant Humicola grisea var. thermoidea cellobiohydrolase presents bifunctional (endo/exoglucanase) activity on cellulosic substrates

Humicola grisea var. thermoidea is a deuteromycete which secretes a large spectrum of hydrolytic enzymes when grown on lignocellulosic residues. This study focused on the heterologous expression and recombinant enzyme analysis of the major secreted cellulase when the fungus is grown on sugarcane bagasse as the sole carbon source. Cellobiohydrolase 1.2 (CBH 1.2) cDNA was cloned in Pichia pastoris under control of the AOX1 promoter. Recombinant protein (rCBH1.2) was efficiently produced and secreted as a functional enzyme, presenting a molecular mass of 47?kDa. Maximum enzyme production was achieved at 96?h, in culture medium supplemented with 1.34?% urea and 1?% yeast extract and upon induction with 1?% methanol. Recombinant enzyme exhibited optimum activity at 60?°C and pH 8, and presented a remarkable thermostability, particularly at alkaline pH. Activity was evaluated on different cellulosic substrates (carboxymethyl cellulose, filter paper, microcrystalline cellulose and 4-para-nitrophenyl ??-d-glucopyranoside). Interestingly, rCBH1.2 presented both exoglucanase and endoglucanase activities and mechanical agitation increased substrate hydrolysis. Results indicate that rCBH1.2 is a potential biocatalyst for applications in the textile industry or detergent formulation.     

Production of cellulosic ethanol in Saccharomyces cerevisiae heterologous expressing Clostridium thermocellum endoglucanase and Saccharomycopsis fibuligera β-glucosidase genes

Heterologous secretory expression of endoglucanase E (Clostridium thermocellum) and β-glucosidase 1 (Saccharomycopsis fibuligera) was achieved in Saccharomyces cerevisiae fermentation cultures as an α-mating factor signal peptide fusion, based on the native enzyme coding sequence. Ethanol production depends on simultaneous saccharification of cellulose to glucose and fermentation of glucose to ethanol by a recombinant yeast strain as a microbial biocatalyst. Recombinant yeast strain expressing endoglucanase and β-glucosidase was able to produce ethanol from β-glucan, CMC and acid swollen cellulose. This indicates that the resultant yeast strain of this study acts efficiently as a whole cell biocatalyst.     

Functional and structural analyses of a 1,4-β-endoglucanase from Ganoderma lucidum

Ganoderma lucidum is a saprotrophic white-rot fungus which contains a rich set of cellulolytic enzymes. Here, we screened an array of potential 1,4-β-endoglucanases from G. lucidum based on the gene annotation library and found that one candidate gene, GlCel5A, exhibits CMC-hydrolyzing activity. The recombinant GlCel5A protein expressed in Pichia pastoris is able to hydrolyze CMC and β-glucan but not xylan and mannan. The enzyme exhibits optimal activity at 60 °C and pH 3–4, and retained 50% activity at 80 and 90 °C for at least 15 and 10 min. The crystal structure of GlCel5A and its complex with cellobiose, solved at 2.7 and 2.86 Å resolution, shows a classical (β/α)₈ TIM-barrel fold as seen in other members of glycoside hydrolase family 5. The complex structure contains a cellobiose molecule in the +1 and +2 subsites, and reveals the interactions with the positive sites of the enzyme. Collectively, the present work provides the first comprehensive characterization of an endoglucanase from G. lucidum that possesses properties for industrial applications, and strongly encourages further studying in the cellulolytic enzyme system of G. lucidum.     

Cloning of novel cellulases from cellulolytic fungi: Heterologous expression of a family 5 glycoside hydrolase from Trametes versicolor in Pichia pastoris

Total cDNA isolated from cellulolytic fungi cultured in cellulose was examined for the presence of sequences encoding for endoglucanases. Novel sequences encoding for glycoside hydrolases (GHs) were identified in Fusarium oxysporum, Ganoderma applanatum and Trametes versicolor. The cDNA encoding for partial sequences of GH family 61 cellulases from F. oxysporum and G. applanatum shares 58 and 68% identity with endoglucanases from Glomerella graminicola and Laccaria bicolor, respectively. A new GH family 5 endoglucanase from T. versicolor was also identified. The cDNA encoding for the mature protein was completely sequenced. This enzyme shares 96% identity with Trametes hirsuta endoglucanase and 22% with Trichoderma reesei endoglucanase II (EGII). The enzyme, named TvEG, has N-terminal family 1 carbohydrate binding module (CBM1). The full length cDNA was cloned into the pPICZαB vector and expressed as an active, extracellular enzyme in the methylotrophic yeast Pichia pastoris. Preliminary studies suggest that T. versicolor could be useful for lignocellulose degradation.     

Role of β-1,3-glucanase in postmeiotic microspore release

Stage-specific extracts of Lilium anthers undergoing meiosis exhibited sharp peaks of both endolytic and exolytic β-1,3-glucanase activity at the time of in situ callose breakdown. The endo- and exo-β-1,3-glucanase activities, attributable to different enzymes, were found to have molecular weights of 32,000 and 62,000, respectively. The majority of exoglucanase activity was found in the outer somatic layers of the anther, whereas the majority of endoglucanase activity was located in the immediate surroundings of the meiocytes. The action of both glucanase activities on callose wall removal was monitored. It was shown that endo-β-1,3-glucanase, but not exoglucanase, was able to effect callose wall removal. To the extent that detection of glucanase activity in extracts reflects its activity in vivo, the endoglucanase enzyme may be considered as the immediate agent of callose wall breakdown and, hence, as a critical regulator in the initiation of the development of the gametophyte stage.     

Characterization of an Endoglucanase from Pseudomonas fluorescens subsp. cellulosa Produced in Escherichia coli and Regulation of the Expression of Its Cloned Gene

Several enzymatic properties of an endoglucanase produced in Escherichia coli by a gene from Pseudomonas fluorescens subsp. cellulosa were investigated. Gel filtration revealed a single peak of M_r 36,000 with endoglucanase activity. The pH optimum of the enzyme was 7.0. Carboxymethyl cellulose and barley β-glucan (mixed β-1,3 and 1,4 linkages) were good substrates, but not laminarin (β-1,3 linkages), amylose, filter paper, microcrystalline cellulose (Avicel), or cellotriose. The mode of action was typical of an “endo”-acting enzyme. Taken together, these properties do not correspond to those of any of the endoglucanases described in P. fluorescens subsp. cellulosa. Consequently, the gene was designated egIX. The enzyme was sensitive to end-product inhibition by cellobiose but was only moderately inhibited by glucose. The enzyme was formed constitutively in E. coli throughout the growth phase. Urea had no effect on endoglucanase synthesis, but glucose acted as a catabolite repressor. The formation of the enzyme in E. coli was partially dependent on cyclic AMP.     

High-Level Expression of Endo-β-N-Acetylglucosaminidase H from Streptomyces plicatus in Pichia pastoris and Its Application for the Deglycosylation of Glycoproteins

Endo-β-N-acetylglucosaminidase H (Endo H, EC3.2.1.96) is a glycohydrolase that is widely used in the study of glycoproteins. The present study aimed to assess the effect of high-level endo-β-N-acetylglucosaminidase H expression in Pichia pastoris. The DNA coding sequence of this enzyme was optimized based on the codon usage bias of Pichia pastoris and synthesized through overlapping PCR. This novel gene was cloned into a pHBM905A vector and introduced into Pichia pastoris GS115 for secretary expression. The yield of the target protein reached approximately 397 mg/l after a 6-d induction with 1% (v/v) methanol in shake flasks, which is much higher than that observed upon heterologous expression in Escherichia coli and silkworm. This recombinant enzyme was purified and its enzymatic features were studied. Its specific activity was 461573 U/mg. Its optimum pH and temperature were pH 5.5 and 37°C, respectively. Moreover, our study showed that the N-linked glycan side-chains of several recombinant proteins expressed in Pichia pastoris can be efficiently removed through either the co-fermentation of this recombinant strain with strains expressing substrates or by mixing the cell culture supernatants of the endo-β-N-acetylglucosaminidase H expressing strain with strains expressing substrates after fermentation. This is the first report of high-level endo-β-N-acetylglucosaminidase H expression in Pichia pastoris and the application of this enzyme in the deglycosylation of raw glycoproteins heterologously expressed in Pichia pastoris using simplified methods.     

Structural analyses and yeast production of the β-1,3-1,4-glucanase catalytic module encoded by the licB gene of Clostridium thermocellum

A thermophilic glycoside hydrolase family 16 (GH16) β-1,3-1,4-glucanase from Clostridium thermocellum (CtLic16A) holds great potentials in industrial applications due to its high specific activity and outstanding thermostability. In order to understand its molecular machinery, the crystal structure of CtLic16A was determined to 1.95 Å resolution. The enzyme folds into a classic GH16 β-jellyroll architecture which consists of two β-sheets atop each other, with the substrate-binding cleft lying on the concave side of the inner β-sheet. Two Bis–Tris propane molecules were found in the positive and negative substrate binding sites. Structural analysis suggests that the major differences between the CtLic16A and other GH16 β-1,3-1,4-glucanase structures occur at the protein exterior. Furthermore, the high catalytic efficacy and thermal profile of the CtLic16A are preserved in the enzyme produced in Pichia pastoris, encouraging its further commercial applications.     

Functional Expression of a Thermostable Endoglucanase from <Emphasis Type="Italic">Thermoascus aurantiacus</Emphasis> RCKK in <Emphasis Type="Italic">Pichia pastoris</Emphasis> X-33 and Its Characterization

Thermostable cellulases offer several advantages like higher rates of substrate hydrolysis, lowered risk of contamination, and increased flexibility with respect to process design. In the present study, a thermostable native endoglucanase nEG (EC 3.2.1.4) was purified and characterized from T. aurantiacus RCKK. Further, it was cloned in P. pastoris X-33 and processed for over expression. Expression of recombinant endoglucanase (rEG) of molecular size ~?33 kDa was confirmed by SDS-PAGE and western blotting followed by in gel activity determination by zymogram analysis. Similar to nEG, the purified rEG was characterized to harbor high thermostability while retaining 50% of its initial activity even after 6- and 10-h incubation at 80 and 70 °C, respectively, and exhibited considerable stability in pH range 3.0–7.0. CD spectroscopy revealed more than 20% β-sheets in protein structure consistently when incubated upto 85 °C as a speculated reason for protein high thermostability. Interestingly, both nEG and rEG were found tolerant up to 10% of the presence of 1-ethyl-3-methylimidazolium acetate [C2mim][OAc]. Values of the catalytic constants K_m and V_max for rEG were recorded as 2.5 mg/ml and 303.4 µmol/mg/min, respectively. Thermostability, pH stability, and resistance to the presence of ionic liquid signify the potential applicability of present enzyme in cellulose hydrolysis and enzymatic deinking of recycled paper pulp.     

Cloning,expression, and molecular dynamics simulations of a xylosidase obtained from Thermomyces lanuginosus

The aim of this study was to clone, express, and characterize a β-xylosidase (Tlxyn1) from the thermophilic fungus Thermomyces lanuginosus SSBP in Pichia pastoris GS115 as well as analyze optimal activity and stability using computational and experimental methods. The enzyme was constitutively expressed using the GAP promoter and secreted into the medium due to the alpha-mating factor secretion signal present on the expression vector pBGPI. The 1276 bp gene consists of an open reading frame that does not contain introns. A 12% SDS–PAGE gel revealed a major protein band at an estimated molecular mass of 50 kDa which corresponded to zymogram analysis. The three-dimensional structure of β-xylosidase was predicted, and molecular dynamics simulations at different ranges of temperature and pH were performed in order to predict optimal activity and folding energy. The results suggested a strong conformational temperature and pH dependence. The recombinant enzyme exhibited optimal activity at pH 7 and 50°C and retained 80% activity at 50°C, pH 7 for about 45 min. This is the first report of the cloning, functional expression, and simulations study of a β-xylosidase from Thermomyces species in a fungal host.     

Cellulase production by Talaromyces emersonii CBS 814.70 and a mutant UV7 during growth on cellulose,lactose and glucose containing media

Recently it has been reported that Talaromyces emersonii CBS 814.70 is capable of growth on lactose containing media. During growth on such media large amounts of β-glucosidase are secreted into the medium. In addition, low levels of endoglucanase activity have been detected. In order to enhance endoglucanase production, u.v. irradiation and a modified selection procedure yielded a number of mutants. One of these, UV7, was capable of increased cellulase production during growth on cellulose, lactose and glucose containing media. Comparative studies between the wild-type organism and the mutant have shown that the former apparently produces constitutive levels of both endoglucanase and β-glucosidase. The form of β-glucosidase that appears to be constitutive is that form previously named BG-I.