Purification and characterization of a thermostable endo-β-1,4-glucanase from a novel strain of Penicillium purpurogenum

Insights into the transcriptomic mechanism and characterization of endoglucanases from Aspergillus terreus in cellulose degradation

Filamentous fungi are the main industrial source of cellulases which are important in the process of converting cellulose to fermentable sugars. In this study, transcriptome analysis was conducted on Aspergillus terreus NEAU-7 cultivated using corn stover and glucose as carbon sources. Four putative endoglucanases (EG5A, EG7A, EG12A, and EG12C) from A. terreus NEAU-7 were efficiently expressed in Pichia pastoris. Among them, EG7A exhibited the highest enzyme activity (75.17 U/mg) with an optimal temperature of 40 °C and pH 5.0. EG5A and EG12A displayed specific activities of 19.92 U/mg and 14.62 U/mg, respectively, at 50 °C. EG12C showed acidophilic characteristics with an optimal pH of 3.0 and a specific activity of 12.21 U/mg at 40 °C. With CMC-Na as the substrate, the Km value of EG5A, EG7A, EG12A or, EG12C was, 11.08 ± 0.87 mg/mL, 6.82 ± 0.74 mg/mL, 7.26 ± 0.64 mg/mL, and 9.88 ± 0.86 mg/mL, with Vmax values of 1258.23 ± 51.62 μmol∙min-1∙mg-1, 842.65 ± 41.53 μmol∙min-1∙mg-1, 499.38 ± 20.42 μmol∙min-1∙mg-1, and 681.41 ± 30.08 μmol∙min-1∙mg-1, respectively. The co-treatment of EG7A with the commercial cellulase increased the yield of reducing sugar by 155.77 % (filter paper) and 130.49 % (corn stover). Molecular docking assay showed the interaction energy of EG7A with cellotetraose at -10.50 kcal/mol, surpassing EG12A (-10.43 kcal/mol), EG12C (-10.28 kcal/mol), and EG5A (-9.00 kcal/mol). Root Mean Square Deviation (RMSD) and Solvent Accessible Surface Area (SASA) values revealed that the presence of cellotetraose stabilized the molecular dynamics simulation of the cellotetraose-protein complex over a 100 ns time scale. This study provides valuable insights for developing recombinant enzymes and biomass degradation technologies.

Purification and enzymatic properties of a new thermostable endoglucanase from Aspergillus oryzae HML366

Aspergillus oryzae HML366 is a newly screened cellulase-producing strain. The endoglucanase HML ED1 from A. oryzae HML366 was quickly purified by a two-step method that combines ammonium sulfate precipitation and strong anion exchange column. SDS-PAGE electrophoresis indicated that the molecular weight of the enzyme was 68 kDa. The optimum temperature of the purified endoglucanase was 60 ℃ and the enzyme activity was stable below 70 ℃. The optimum pH was 6.5, and the enzyme activity was stable at pH between 4.5 and 9.0. The analysis indicated that additional Na⁺, K⁺, Ca²⁺, and Zn²⁺ reduced the catalytic ability of enzyme to the substrate, but Mn²⁺ enhanced its catalytic ability to the substrate.The Km and Vmax of the purified endoglucanase were 8.75 mg/mL and 60.24 μmol/min·mg, respectively. In this study, we report for the first time that A. oryzae HML366 can produce a heat-resistant and wide pH tolerant endoglucanase HML ED1, which has potential industrial application value in bioethanol, paper, food, textile, detergent, and pharmaceutical industries.

Expression, characterization, and activity optimization of a novel cellulase from the thermophilic bacteria Cohnella sp. A01

Cellulases are hydrolytic enzymes with wide scientific and industrial applications. We described a novel cellulase, CelC307, from the thermophilic indigenous Cohnella sp. A01. The 3-D structure of the CelC307 was predicted by comparative modeling. Docking of CelC307 with specific inhibitors and molecular dynamic (MD) simulation revealed that these ligands bound in a non-competitive manner. The CelC307 protein was purified and characterized after recombinant expression in Escherichia coli (E. coli) BL21. Using CMC 1% as the substrate, the thermodynamic values were determined as K_m 0.46 mM, k_cat 104.30 × 10^-3 (S^-1), and k_cat/K_m 226.73 (M^-1 S^-1). The CelC307 was optimally active at 40 °C and pH 7.0. The culture condition was optimized for improved CelC307 expression using Plackett-Burman and Box-Behnken design as follows: temperature 20 °C, pH 7.5, and inoculation concentration with an OD₆₀₀ = 1. The endoglucanase activity was positively modulated in the presence of Na⁺, Li⁺, Ca²⁺, 2-mercaptoethanol (2-ME), and glycerol. The thermodynamic parameters calculated for CelC307 confirmed its inherent thermostability. The characterized CelC307 may be a suitable candidate for various biotechnological applications.

Improved deinking and biobleaching efficiency of enzyme consortium from Thermomyces lanuginosus VAPS25 using genetic Algorithm-Artificial neural network based tools

The present study reports the combined enzymatic production efficiency of thermophilic fungus Thermomyces lanuginosus VAPS25 using a combinatory artificial intelligence-based tool, resulting in 2.7 IU/ml, 5.2 IU/ml, and 18.85 U/ml activity of endoglucanase, amylase, and lipase, respectively with good thermostability at 90 °C (pH 8-10). Interestingly, the metal ions viz. Cu²⁺ and Mg²⁺ increased the endoglucanase activity to 5 folds, i.e.,5.6 IU/ml compared to control. Further, the amylase and lipase activity was also enhanced by Fe²⁺ and Co²⁺ to 5.4 IU/ml and 19.57 U/ml, respectively. Additionally, the deinking efficiency was improved by 68.9%, 42.7%, and 52.8% by endoglucanase, amylase, and lipase, respectively, while the consortium increased the deinking efficiency to 72.7%. The bio-bleached paper strength parameters such as burst index, breaking length, tear index, and tensile index of sheets were significantly improved by 1.38%, 13.54%, 7.54%, and 20.88%, respectively. These enzymes at an industrial scale would help develop an economical paper recycling process.

Heterologous expression and biochemical characterization of a thermostable endo-β-1,4-glucanase from Colletotrichum orchidophilum

To develop new cellulases for efficient utilization of the lignocellulose, an endoglucanase (CoCel5A) gene from Colletotrichum orchidophilum was synthesized and a recombinant Pichia pastoris GS115/pPIC9K/cocel5A was constructed for secretory expression of CoCel5A. After purification, the protein CoCel5A was biochemically characterized. The endoglucanase CoCel5A exhibited the optimal activity at 55-75 °C and high thermostability (about 85% residual activity) at the temperature of 55 °C after incubation for 3 h. The highest activity of CoCel5A was detected when 100 mM citric acid buffer (pH 4.0-5.0) was used and excellent pH stability (up to 95% residual activity) was observed after incubation in 100 mM citric acid buffer (pH 3.0-6.0) at 4 °C for 24 h. Carboxymethyl cellulose sodium salt (n = approx. 500) (CMC) and β-D-glucan were the best substrates for CoCel5A among the tested substrates. The kinetic parameters V_max, K_m, and K_cat/K_m values against CMC were 290.70 U/mg, 2.65 mg/mL, and 75.67 mL/mg/s, respectively; and 228.31 U/mg, 2.06 mg/mL, and 76.45 mL/mg/s against β-D-glucan, respectively, suggesting that CoCel5A has high affinity and catalytic efficiency. These properties supported the potential application of CoCel5A in biotechnological and environmental fields.

A Novel Cold-Adaptive Endo-1,4-β-Glucanase From Burkholderia pyrrocinia JK-SH007: Gene Expression and Characterization of the Enzyme and Mode of Action

The efficient industrial conversion of plant-derived cellulose to simple sugars and other value-added chemicals requires various highly stable and reactive enzymes. Industrial processes especially synchronous saccharification and fermentation (SSF)-based production of cellulosic bio-ethanol require enzymes that are active at lower temperatures. In this study, we have identified, characterized, and expressed the cold-adaptive endo-1,4-β-glucanase (BpEG) isolated from the Burkholderia pyrrocinia JK-SH007. The analysis of the predicted amino acid sequence indicated that BpEG belongs to GH family 8. The BpEG without the signal peptide was cloned into the expression vector pET32a and significantly expressed in Escherichia coli BL21 (DE3) competent cells. The SDS-PAGE and Western blot analysis of BpEG revealed that the recombinant BpEG was approximately 60 kDa. Purified recombinant BpEG exhibited hydrolytic activity against carboxymethyl cellulose (CMC) and phosphoric acid swollen cellulose (PASC), but not crystalline cellulose and xylan substrates. High performance, anion exchange, chromatography-pulsed amperometric detector (HPAEC-PAD) analysis of the enzymatic products obtained from depolymerization of 1,4-β-linked biopolymers of different lengths revealed an interesting cutting mechanism employed by endoglucanases. The recombinant BpEG exhibited 6.0 of optimum pH and 35°C of optimum temperature, when cultured with CMC substrate. The BpEG enzyme exhibited stable activity between pH 5.0 and 9.0 at 35°C. Interestingly, BpEG retained about 42% of its enzymatic activity at 10°C compared to its optimal temperature. This new cold-adaptive cellulase could potentially achieve synchronous saccharification and fermentation (SSF) making BpEG a promising candidate in the fields of biofuel, biorefining, food and pharmaceutical industries.

Activity and Thermostability of GH5 Endoglucanase Chimeras from Mesophilic and Thermophilic Parents

Cellulases from glycoside hydrolase family 5 (GH5) are key endoglucanase enzymes in the degradation of diverse polysaccharide substrates and are used in industrial enzyme cocktails to break down biomass. The GH5 family shares a canonical (βα)8-barrel structure, where each (βα) module is essential for the enzyme's stability and activity. Despite their shared topology, the thermostability of GH5 endoglucanase enzymes can vary significantly, and highly thermostable variants are often sought for industrial applications. Based on the previously characterized thermophilic GH5 endoglucanase Egl5A from Talaromyces emersonii (TeEgl5A), which has an optimal temperature of 90°C, we created 10 hybrid enzymes with elements of the mesophilic endoglucanase Cel5 from Stegonsporium opalus (SoCel5) to determine which elements are responsible for enhanced thermostability. Five of the expressed hybrid enzymes exhibit enzyme activity. Two of these hybrids exhibited pronounced increases in the temperature optimum (10 and 20°C), the temperature at which the protein lost 50% of its activity (T50) (15 and 19°C), and the melting temperature (Tm ) (16.5 and 22.9°C) and extended half-lives (t1/2) (∼240- and 650-fold at 55°C) relative to the values for the mesophilic parent enzyme and demonstrated improved catalytic efficiency on selected substrates. The successful hybridization strategies were validated experimentally in another GH5 endoglucanase, Cel5 from Aspergillus niger (AnCel5), which demonstrated a similar increase in thermostability. Based on molecular dynamics (MD) simulations of both the SoCel5 and TeEgl5A parent enzymes and their hybrids, we hypothesize that improved hydrophobic packing of the interface between α2 and α3 is the primary mechanism by which the hybrid enzymes increase their thermostability relative to that of the mesophilic parent SoCel5.IMPORTANCE Thermal stability is an essential property of enzymes in many industrial biotechnological applications, as high temperatures improve bioreactor throughput. Many protein engineering approaches, such as rational design and directed evolution, have been employed to improve the thermal properties of mesophilic enzymes. Structure-based recombination has also been used to fuse TIM barrel fragments, and even fragments from unrelated folds, to generate new structures. However, little research has been done on GH5 endoglucanases. In this study, two GH5 endoglucanases exhibiting TIM barrel structure, SoCel5 and TeEgl5A, with different thermal properties, were hybridized to study the roles of different (βα) motifs. This work illustrates the role that structure-guided recombination can play in helping to identify sequence function relationships within GH5 enzymes by supplementing natural diversity with synthetic diversity.

Production, purification, characterization and application of a new halotolerant and thermostable endoglucanase of Botrytis ricini URM 5627

A halotolerant endoglucanase with a molecular mass of 39 kDa was obtained from the solid fermentation of sugarcane bagasse by the fungus Botrytis ricini URM 5627 and isolated using only two purification processes: fractionation with ammonium sulphate and size-exclusion chromatography resulting in an activity of 1289.83 U/mL. After the isolation, biochemical characterizations were performed, giving a temperature of 50 °C and optimum pH of 5. The enzyme was stable at 39-60 °C for 60 min and at a pH of 4-6. The enzymatic activity increased in the presence of Na⁺, Mn²⁺, Mg²⁺ and Zn²⁺ and decreased in the presence of Ca²⁺, Cu²⁺, and Fe²⁺. The endoglucanase revealed a halotolerant profile since its activity increased proportionally to an increase in NaCl concentration. The maximum activity was reached at 2 M NaCl with a 75% increase in activity. The enzyme had a K_m of 0.1299 ± 0.0096 mg/mL and a V_max of 0.097 ± 0.00121 mol/min/mL. During application in saccharification tests, the enzyme was able to hydrolyse sugarcane bagasse, rice husk, and wheat bran, with the highest production of reducers/fermentable sugars within 24 h of saccharification for wheat bran (137.21 mg/g). Therefore, these properties combined make this isolated enzyme a potential candidate for biotechnological and industrial applications.

Improvement of the catalytic performance of a Bispora antennata cellulase by replacing the N-terminal semi-barrel structure

The aim of this work was to study the contribution of the N-terminal structure to cellulase catalytic performance. A wild-type cellulase (BaCel5) of glycosyl hydrolase (GH) family 5 from Bispora antennata and two hybrid enzymes (BaCel5(127) and BaCel5(167)) with replacement of the N-terminal (βα)3 (127 residues) or (βα)4 (167 residues)-barrel with the corresponding sequences of TeEgl5A from Talaromyces emersonii were produced in Pichia pastoris and biochemically characterized. BaCel5 exhibited optimal activity at pH 5.0 and 50°C but had low catalytic efficiency (25.4±0.8mLs(-1)mg(-1)). In contrast, BaCel5(127) and BaCel5(167) showed similar enzymatic properties but improved catalytic performance. When using CMC-Na, barley β-glucan, lichenan, and cellooligosaccharides as substrates, BaCel5(127) and BaCel5(167) had increased specific activities and catalytic efficiencies by ∼1.8-6.7-fold and ∼1.0-4.7-fold, respectively. The catalytic efficiency of BaCel5(167) was even higher than that of parental proteins. The underlying mechanism was analyzed by molecular docking and molecular dynamic simulation.

NaCl-, protease-tolerant and cold-active endoglucanase from Paenibacillus sp. YD236 isolated from the feces of Bos frontalis

Bos frontalis, which consumes bamboo and weeds, may have evolved unique gastrointestinal microorganisms that digest cellulase. A Paenibacillus sp. YD236 strain was isolated from B. frontalis feces, from which a GH8 endoglucanase gene, pglue8 (1107 bp, 54.5 % GC content), encoding a 368-residue polypeptide (PgluE8, 40.4 kDa) was cloned. PgluE8 efficiently hydrolyzed barley-β-d-glucan followed by CMC-Na, soluble starch, laminarin, and glucan from black yeast optimally at pH 5.5 and 50 °C, and retained 78.6, 41.6, and 34.5 % maximum activity when assayed at 20, 10, and 0 °C, respectively. Enzyme activity remained above 176.6 % after treatment with 10.0 mM β-mercaptoethanol, and was 83.0, 78, and 56 % after pre-incubation in 30 % (w/v) NaCl, 16.67 mg/mL trypsin, and 160.0 mg/mL protease K, respectively. Cys23 and Cys364 residues were critical for PgluE8 activity. pglue8, identified from B. frontalis feces for the first time in this study, is a potential alternative for applications including food processing, washing, and animal feed preparation.

Characteristics of free endoglucanase and glycosidases multienzyme complex from Fusarium verticillioides

A novel multienzyme complex, E1C, and a free endoglucanase, E2 (GH5), from Fusarium verticillioides were purified. The E1C contained two endoglucanases (GH6 and GH10), one cellobiohydrolase (GH7) and one xylanase (GH10). Maximum activity was observed at 80 °C for both enzymes and they were thermostable at 50 and 60 °C. The activation energies for E1C and E2 were 21.3 and 27.5 kJ/mol, respectively. The KM for E1C was 10.25 g/L while for E2 was 6.58 g/L. Both E1C and E2 were activated by Mn(2+) and CoCl2 while they were inhibited by SDS, CuSO4, FeCl3, AgNO4, ZnSO4 and HgCl2. E1C and E2 presented endo-β-1,3-1,4-glucanase activity. E1C presented crescent activity towards cellopentaose, cellotetraose and cellotriose. E2 hydrolyzed the substrates cellopentaose, cellotetraose and cellotriose with the same efficiency. E1C showed a higher stability and a better hydrolysis performance than E2, suggesting advantages resulting from the physical interaction between proteins.

Characterisation of acid proteases from a fusant F76 and its progenitors Aspergillus oryzae HN3042 and Aspergillus niger CICC2377

The characteristics of a novel acid protease from a fusant F76 were comparatively evaluated with those from its progenitors Aspergillus oryzae HN3042 and A. niger CICC2377. The UV spectra of these three acid proteases were similar, but fluorescence spectra were different. The acid protease from F76 contained 7.1% α‐helix, 39.4% β‐sheet, 24.7% β‐turn and 32% aperiodic coil, unlike those from its progenitors. The acid protease from F76 was active in the temperature range of 35–55 °C with the optimum temperature of 40 °C and was stable in the pH range of 2.5–6.5 with the optimum pH of 3.5, while those values from A. oryzae HN3042 and A. niger CICC2377 were 45 °C, 4.0 and 40 °C, 3.5, respectively. The kinetic parameters of the acid protease from F76 were different from its progenitors and the Michaelis constant, maximum velocity, activation energy, and attenuation index were 0.96 mg mL−1, 135.14 μmol min−1 mg−1, 64.11 kJ mol−1 and 0.59, respectively.

High-level expression of a novel Penicillium endo-1,3(4)-β-d-glucanase with high specific activity in Pichia pastoris

A novel endo-1,3(4)-β-d-glucanase gene (bgl16C1) from Penicillium pinophilum C1 was cloned and sequenced. The 945-bp full-length gene encoded a 315-residue polypeptide consisting of a putative signal peptide of 18 residues and a catalytic domain belonging to glycosyl hydrolase family 16. The deduced amino acid sequence showed the highest identity (82%) with the putative endo-1,3(4)-β-glucanase from Talaromyces stipitatus ATCC 10500 and 60% identity with the characterized β-1,3(4)-glucanase from Paecilomyces sp. FLH30. The gene was successfully overexpressed in Pichia pastoris. Recombinant Bgl16C1 constituted 95% of total secreted proteins (2.61 g l−1) with activity of 28,721 U ml−1 in a 15-l fermentor. The purified recombinant Bgl16C1 had higher specific activity toward barley β-glucan (12,622 U mg−1) than all known glucanases and also showed activity against lichenan and laminarin. The enzyme was optimally active at pH 5.0 and 55°C and exhibited good stability over a broad acid and alkaline pH range (>85% activity at pH 3.0–7.0 and even 30% at pH 11.0). All these favorable enzymatic properties make it attractive for potential applications in various industries.

Expression of an endo-β-1,4-glucanase gene from orpinomyces PC-2 in Pichia pastoris

The endo-β-1,4-glucanase gene celE from the anaerobic fungus Orpinomyces PC-2 was placed under the control of an alcohol oxidase promoter (AOX1) in the plasmid pPIC9K, and integrated into the genome of a methylotrophic yeast P. pastoris GS115 by electroporation. The strain with highest endo-β-1,4-glucanase activity was selected and designed as P. pastoris egE, and cultivated in shaking flasks. The culture supernatant was assayed by SDS-polyacrylamide gel electrophoresis and showed a single band at about 52 kDa. Furthermore, the recombinant P. pastoris egE was proved to possess the ability to utilize sodium carboxymethyl cellulose as a carbon source. The recombinant endoglucanase produced by P. pastoris showed maximum activity at pH 6.0 and temperature 45 °C, indicating it was a mesophilic neutral endo-β-1,4-glucanase, suitable for denim biofinishing/washing. Further research was carried out in suitable fermentation medium in shaking flasks. The most favorable methanol addition concentration was discussed and given as 1.0%. After methanol induction for 96 h, the endo-β-1,4-glucanase activity reached 72.5 IU mL⁻¹. This is the first report on expression and characterization of endo-β-1,4-glucanase from Orpinomyces in P. pastoris. The endo-β-1,4-glucanase secreted by recombinant P. pastoris represents an attractive potential for both academic research and textile industry application.

Effect of the ash on enzymatic hydrolysis of steam-exploded rice straw

The effect of metal ions in ash on enzymatic hydrolysis of crop straw has not attracted sufficient attention. In present study, rice straw with high ash content was taken as an example to study the effect. It was found that the common cations of ash (K(+), Mg(2+), Ca(2+), Al(3+), Mn(2+), Fe(3+), Cu(2+), and Zn(2+)) all showed inhibitive effects on cellulase at different levels, except for the stimulative effects of Ca(2+) and Mg(2+) on beta-glucosidase. Interestingly, washing treatment, combined with steam explosion, could effectively remove the ash cations of rice straw. The kinetic study of enzymatic hydrolysis indicated that, compared with the unwashed steam-exploded rice straw (SERS), the maximal hydrolysis velocity of washed SERS was increased by 12.5%. Therefore, the removal of ash by washing could facilitate the enzymatic hydrolysis of SERS.