Cloning of a β-1,3-1,4-Glucanase Gene from Bacillus subtilis MA139 and its Functional Expression in Escherichia coli

Expression and biochemical characterization of a novel thermostable alkaline β-1,3-1,4-glucanase (lichenase) from an alkaliphilic Bacillus lehensis G1

New thermostable β-1,3-1,4-glucanase (lichenase) designated as Blg29 was expressed and purified from a locally isolated alkaliphilic bacteria Bacillus lehensis G1. The genome sequence of B. lehensis predicted an open reading frame of Blg29 with a deduced of 249 amino acids and a molecular weight of 28.99 kDa. The gene encoding for Blg29 was successfully amplified via PCR and subsequently expressed as a recombinant protein using the E. coli expression system. Recombinant Blg29 was produced as a soluble form and further purified via immobilized metal ion affinity chromatography (IMAC). Based on biochemical characterization, recombinant Blg29 showed optimal activity at pH9 and temperature 60 °C respectively. This enzyme was stable for more than 2 h, incubated at 50 °C, and could withstand ∼50 % of its activity at 70 °C for an hour and a half. No significant effect on Blg29 was observed when incubated with metal ions except for a small increase with ion Ca2+. Blg29 showed high substrate activity towards lichenan where Vm, Km, Kcat, and kcat/Km values were 2040.82 μmolmin‾1mg‾1, 4.69 mg/mL, and 986.39 s‾1 and 210.32 mLs‾1mg‾1 respectively. The high thermostability and activity make this enzyme useable for a broad prospect in industry applications.

Biochemical properties and application of a multi-domain β-1,3-1,4-glucanase from Fibrobacter sp

A novel glycoside hydrolase (GH) family 16 multi-domain β-1,3-1,4-glucanase (FsGlc16A) from Fibrobacter sp. UWP2 was identified, heterogeneously expressed, and its enzymatic properties, protein structure and application potential were characterized. Enzymological characterization showed that FsGlc16A performed the optimal catalytic activity at pH 4.5 and 50 °C with a specific activity of 3263 U/mg. FsGlc16A exhibited the substrate specificity towards oat β-glucan, barley β-glucan and lichenan, and in addition, it hydrolyzed oat β-glucan and lichenan into different β-glucooligosaccharides with polymerization degrees of 3-4, which further illustrated that it belonged to the endo-type β-1,3-1,4-glucanase. FsGlc16A was classified in subfamily25 of GH16. A 'PXSSSS' repeats domain was identified at the C-terminus of FsGlc16A, which was distinct from the typical GH family 16 β-1,3-1,4-glucanases. Removing the 'PXSSSS' repeats domain affected the binding of the substrate to FsGlc16A and reduced the enzyme activity. FsGlc16A displayed good potential for the applications, which hydrolyzed oat bran into β-glucooligosaccharides, and reduced filtration time (18.89 %) and viscosity (3.64 %) in the saccharification process. This study investigated the enzymatic properties and domain function of FsGlc16A, providing new ideas and insights into the study of β-1,3-1,4-glucanase.

Characterization of Cellulose-Degrading Bacteria Isolated from Soil and the Optimization of Their Culture Conditions for Cellulase Production

The characterization of bacteria with hydrolytic potential significantly contributes to the industries. Six cellulose-degrading bacteria were isolated from mixture soil samples collected at Kingfisher Lake and the University of Manitoba campus by Congo red method using carboxymethyl cellulose agar medium and identified as Paenarthrobacter sp. MKAL1, Hymenobacter sp. MKAL2, Mycobacterium sp. MKAL3, Stenotrophomonas sp. MKAL4, Chryseobacterium sp. MKAL5, and Bacillus sp. MKAL6. Their cellulase production was optimized by controlling different environmental and nutritional factors such as pH, temperature, incubation period, substrate concentration, nitrogen, and carbon sources using the dinitrosalicylic acid and response surface methods. Except for Paenarthrobacter sp. MKAL1, all strains are motile. Only Bacillus sp. MKAL6 was non-salt-tolerant and showed gelatinase activity. Sucrose enhanced higher cellulase activity of 78.87 ± 4.71 to 190.30 ± 6.42 U/mL in these strains at their optimum pH (5-6) and temperature (35-40 °C). The molecular weights of these cellulases were about 25 kDa. These bacterial strains could be promising biocatalysts for converting cellulose into glucose for industrial purposes.

Characterization of a Thermostable Lichenase from Bacillus subtilis B110 and Its Effects on β-Glucan Hydrolysis

Lichenase is an enzyme mainly implicated in the degradation of polysaccharides in the cell walls of grains. Emerging evidence shows that a highly efficient expression of a thermostable recombinant lichenase holds considerable promise for application in the beer-brewing and animal feed industries. Herein, we cloned a lichenase gene (CelA203) from Bacillus subtilis B110 and expressed it in E. coli. This gene contains an ORF of 729 bp, encoding a protein with 242 amino acids and a calculated molecular mass of 27.3 kDa. According to the zymogram results, purified CelA203 existed in two forms, a monomer, and a tetramer, but only the tetramer had potent enzymatic activity. CelA203 remained stable over a broad pH and temperature range and retained 40% activity at 70°C for 1 h. The K_m and V_max of CelA203 towards barley β-glucan and lichenan were 3.98 mg/ml, 1017.17 U/mg, and 2.78 mg/ml, 198.24 U/mg, respectively. Furthermore, trisaccharide and tetrasaccharide were the main products obtained from CelA203-mediated hydrolysis of deactivated oat bran. These findings demonstrate a promising role for CelA203 in the production of oligosaccharides in animal feed and brewing industries.

A trimodular family 16 glycoside hydrolase from the cellulosome of Ruminococcus flavefaciens displays highly specific licheninase (EC 3.2.1.73) activity

Cellulosomes are highly complex cell-bound multi-enzymatic nanomachines used by anaerobes to break down plant carbohydrates. The genome sequence of Ruminococcus flavefaciens revealed a remarkably diverse cellulosome composed of more than 200 cellulosomal enzymes. Here we provide a detailed biochemical characterization of a highly elaborate R. flavefaciens cellulosomal enzyme containing an N-terminal dockerin module, which anchors the enzyme into the multi-enzyme complex through binding of cohesins located in non-catalytic cell-bound scaffoldins, and three tandemly repeated family 16 glycoside hydrolase (GH16) catalytic domains. The DNA sequence encoding the three homologous catalytic domains was cloned and hyper-expressed in Escherichia coli BL21 (DE3) cells. SDS-PAGE analysis of purified His₆ tag containing RfGH16_21 showed a single soluble protein of molecular size ~89 kDa, which was in agreement with the theoretical size, 89.3 kDa. The enzyme RfGH16_21 exhibited activity over a wide pH range (pH 5.0-8.0) and a broad temperature range (50-70 °C), displaying maximum activity at an optimum pH of 7.0 and optimum temperature of 55 °C. Substrate specificity analysis of RfGH16_21 revealed maximum activity against barley β-d-glucan (257 U mg^-1) followed by lichenan (247 U mg^-1), but did not show significant activity towards other tested polysaccharides, suggesting that it is specifically a β-1,3-1,4-endoglucanase. TLC analysis revealed that RfGH16_21 hydrolyses barley β-d-glucan to cellotriose, cellotetraose and a higher degree of polymerization of gluco-oligosaccharides indicating an endo-acting catalytic mechanism. This study revealed a fairly high, active and thermostable bacterial endo-glucanase which may find considerable biotechnological potentials.

Bacterial cellulase from the intestinal tract of the sugarcane borer

Cellulolytic enzymes have wide use in several industrial segments (e.g. biofuels, pulp and paper, food, and cosmetics). However, one of the challenges is their large-scale production with high specific activity to eliminate the dependence of the purchase of enzymatic cocktails produced by commercial parties. The aims of this study were (1) isolation, selection, and partial characterization of bacterial cellulases present in the intestinal tract of the sugarcane borer and (2) to identify cellulase-producing bacteria by analyzing the 16S rDNA gene. Cellulase production and purification assays resulted in similar electrophoretic profiles between four bacterial strains. These strains were identified as Klebsiella pneumoniae, Klebsiella sp., and Bacillus sp. K. pneumoniae was the main cellulase-producing microorganism. Our results show the possibility of finding cellulolytic microorganisms that inhabit the gut of herbivorous animals, especially those that are predators of important crops of economic value. Furthermore, K. pneumoniae cellulase is of medical importance. In hospitals, health professionals, hospital technicians, patients and visitors wear clothes containing cellulose. Thus, K. pneumoniae within hospitals can contaminate these clothes and be spread to the environment. In that case, it would be important for the hospital's chemical sterilization products to have at least one cellulase inhibitor.

Improvement of enzyme activity of β-1,3-1,4-glucanase from Paenibacillus sp. X4 by error-prone PCR and structural insights of mutated residues

β-1,3-1,4-Glucanase (BGlc8H) from Paenibacillus sp. X4 was mutated by error-prone PCR or truncated using termination primers to improve its enzyme properties. The crystal structure of BGlc8H was determined at a resolution of 1.8 Å to study the possible roles of mutated residues and truncated regions of the enzyme. In mutation experiments, three clones of EP 2-6, 2-10, and 5-28 were finally selected that exhibited higher specific activities than the wild type when measured using their crude extracts. Enzyme variants of BG_2-6, BG_2-10, and BG_5-28 were mutated at two, two, and six amino acid residues, respectively. These enzymes were purified homogeneously by Hi-Trap Q and CHT-II chromatography. Specific activity of BG_5-28 was 2.11-fold higher than that of wild-type BG_wt, whereas those of BG_2-6 and BG_2-10 were 0.93- and 1.19-fold that of the wild type, respectively. The optimum pH values and temperatures of the variants were nearly the same as those of BG_wt (pH 5.0 and 40 °C, respectively). However, the half-life of the enzyme activity and catalytic efficiency (k _cat/K _m) of BG_5-28 were 1.92- and 2.12-fold greater than those of BG_wt at 40 °C, respectively. The catalytic efficiency of BG_5-28 increased to 3.09-fold that of BG_wt at 60 °C. These increases in the thermostability and catalytic efficiency of BG_5-28 might be useful for the hydrolysis of β-glucans to produce fermentable sugars. Of the six mutated residues of BG_5-28, five residues were present in mature BGlc8H protein, and two of them were located in the core scaffold of BGlc8H and the remaining three residues were in the substrate-binding pocket forming loop regions. In truncation experiments, three forms of C-terminal truncated BGlc8H were made, which comprised 360, 286, and 215 amino acid residues instead of the 409 residues of the wild type. No enzyme activity was observed for these truncated enzymes, suggesting the complete scaffold of the α₆/α₆-double-barrel structure is essential for enzyme activity.

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.

Improvement of the thermostability and catalytic efficiency of a highly active β-glucanase from Talaromyces leycettanus JCM12802 by optimizing residual charge-charge interactions

BACKGROUND

β-Glucanase is one of the most extensively used biocatalysts in biofuel, food and animal feed industries. However, the poor thermostability and low catalytic efficiency of most reported β-glucanases limit their applications. Currently, two strategies are used to overcome these bottlenecks, i.e., mining for novel enzymes from extremophiles and engineering existing enzymes.

RESULTS

A novel endo-β-1,3-1,4-glucanase of GH16 (Tlglu16A) from the thermophilic fungus Talaromyces leycettanus JCM12802 was produced in Pichia pastoris and characterized. For potential industrial applications, recombinant TlGlu16A exhibits favorable enzymatic properties over most reported glucanases, i.e., remarkable stability over a wide pH range from 1.0 to 10.0 and superior activity on glucan substrates (up to 15,197 U/mg). The only weakness of TlGlu16A is the thermolability at 65 °C and higher. To improve the thermostability, the enzyme thermal stability system was then used to engineer TlGlu16A through optimization of residual charge-charge interactions. Eleven mutants were constructed and compared to the wild-type TlGlu16A. Four mutants, H58D, E134R, D235G and D296K, showed longer half-life time at 80 °C (31, 7, 25, 22 vs. 0.5 min), and two mutants, D235G and D296K, had greater specific activities (158.2 and 122.2 %, respectively) and catalytic efficiencies (k cat/K m, 170 and 114 %, respectively).

CONCLUSIONS

The engineered TlGlu16A has great application potentials from the perspectives of enzyme yield and properties. Its thermostability and activity were apparently improved in the engineered enzymes through charge optimization. This study spans the genetic, functional and structural fields, and provides a combination of gene mining and protein engineering approaches for the systematic improvement of enzyme performance.

Engineering of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 to improve its catalytic efficiency

BACKGROUND

Error-prone polymerase chain reaction (PCR) is frequently used in directed evolution of enzymes to modify their quality. In this study, error-prone PCR was used to improve the catalytic efficiency of β-1,3-1,4-glucanase from Bacillus altitudinis YC-9.

RESULTS

By screening, the mutant Glu-3060 with higher activity was selected among 5000 transformants. After induction with isopropyl β-D-1-thiogalactopyranoside (IPTG), the activity of the mutant Glu-3060 reached 474.6 U mL(-1), resulting in a 48.6% increment of the parent enzyme activity. Research on the characterization of the mutated enzyme showed the optimal pH of the mutated enzyme to be 5.0, which is lower than the parent enzyme, but thermal stability was almost the same between them. Sequence analysis of the mutated enzyme revealed that three amino acids were changed compared with the parent enzyme, including K142N, Q203L and N214D.

CONCLUSION

The three-dimensional structure predicted by SWISS-MODEL of the mutated enzyme Glu-3060 showed that the substitution of three amino acids had an effect on the catalytic activity, stability and optimal pH of the enzyme, through changing the charge properties or electron density, forming secondary keys, the acidity of the amino acids and the side chain group. The sum effects of all the factors were increased activity of the mutated enzyme and decreased optimal pH, while the same thermostability was maintained, thereby increasing the suitability of the enzyme for industrial use.

Energy and ileal digestible amino Acid concentrations for growing pigs and performance of weanling pigs fed fermented or conventional soybean meal

A new strategy of co-inoculating Bacillus subtilis MA139 with Streptococcus thermophilus and Saccharomyces cerevisiae was used to produce fermented soybean meal (FSBM). Three experiments were conducted to determine the concentration of digestible energy (DE) and metabolizable energy (ME) (Exp. 1), apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids (AA) (Exp. 2), and feeding value (Exp. 3) of FSBM produced by this new strategy (NFSB) compared with soybean meal (SBM) and conventionally available FSBM (Suprotein). In Exp. 1, twenty-four barrows (initial body weight [BW] of 32.2 ±1.7 kg) were randomly allotted to 1 of 4 diets with 6 replicates per diet. A corn basal diet and 3 diets based on a mixture of corn and 1 of 3 soybean products listed above were formulated and the DE and ME contents were determined by the difference method. The results showed that there were no differences in DE and ME between SBM and either FSBM product (p>0.05). In Exp. 2, eight barrows (initial BW of 26.8±1.5 kg) were fitted with ileal T-cannulaes and used in a replicated 4×4 Latin square design. Three corn-starch-based diets were formulated using each of the 3 soybean products as the sole source of AA. A nitrogen-free diet was also formulated to measure endogenous losses of AA. The results showed that the SID of all AA except arginine and histidine was similar for NFSB and SBM (p>0.05), but Suprotein had greater (p<0.05) SID of most AA except lysine, aspartate, glycine and proline than NFSB. In Exp. 3, a total of 144 piglets (initial BW of 8.8±1.2 kg) were blocked by weight and fed 1 of 4 diets including a control diet with 24% SBM as well as diets containing 6% and 12% NFSB or 12% Suprotein added at the expense of SBM. During d 15 to 28, replacing SBM with 6% NFSB significantly improved average daily gain (ADG) and average daily feed intake (ADFI) (p<0.05) for nursery piglets. During the overall experiment, ADG of piglets fed diets containing 6% NFSB was significantly greater (p<0.05) than that of piglets fed SBM. In conclusion, fermentation with the new strategy did not affect the energy content or the AID and the SID of AA in SBM. However, inclusion of 6% NFSB in diets fed to nursery piglets improved performance after weaning likely as a result of better nutritional status and reduced immunological challenge.

Characterization of a new 1,3-1,4-β-glucanase gene from Bacillus tequilensis CGX5-1

1,3-1,4-β-Glucanase received great interest due to its application in brewing and feed industries. Application of 1,3-1,4-β-glucanase in brewing industry helps make up for the defect that plant-derived β-glucanases are heat-sensitive. A new strain, CGX5-1, exhibited remarkable 1,3-1,4-β-glucanase, was isolated from Asian giant hornet nest and identified Bacillus tequilensis. Moreover, a new 1,3-1,4-β-glucanase gene from B. tequilensis was cloned and measured to be 720 bp encoding 239 amino acids, with a predicted molecular weight of 26.9 kDa. After expressed in Escherichia coli BL21, active recombinant enzyme of 24 kDa was detected in the supernatant of cell culture, with the activity of 2,978.2 U/mL. The new enzyme was stable in the pH 5.0-7.5 with the highest activity measured at pH 6.0. Moreover, it is thermostable within 45 to 60 °C. The property of the new recombinant enzyme makes this enzyme a broad prospect in brewing industry. Moreover, this is the first report on 1,3-1,4-β-glucanase produced by B. tequilensis.

Purification and characterization of a novel lichenase from Bacillus licheniformis GZ-2

A novel lichenase from Bacillus licheniformis GZ-2 was purified to homogeneity by two steps ion-exchange chromatography with a specific activity of 8231.3 U/mg. The purified enzyme showed as a single protein band with a molecular mass of 25 kDa. The optimum pH and temperature for the enzyme activity were 6.5 and 60 °C, respectively. The enzyme exhibited strict specificity for β-1,3-1,4-d-glucans. The kinetic parameters Km and Vmax were 5.11 mg/mL and 2097 µmol/Min/mg for lichenan and 7.42 mg/mL and 1440 µmol/Min/mg for barley β-glucan. Compared to most of the reported β-1,3-1,4-glucanases (lichenase), the activity of the purified enzyme for lichenan was much higher than that for barley β-glucan. The main products of β-glucan hydrolyzed by the lichenase were cellubiosyltriose (DP3) and cellutriosyltraose (DP4). The lichenase gene from B. licheniformis GZ-2 was cloned and sequenced. The open reading frame of gene gz-2 contained 642 bp coding for a 214 amino acid mature protein. The gene was cloned into an expression vector pET 28a and expressed in Escherichia coli BL21. The activity in cell lysate supernatant was 137.9 U/mg.

Purification, characterization, and heterologous expression of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9

Purification, characterization, gene cloning, and heterologous expression in Escherichia coli of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 have been investigated in this paper. The donor strain B. altitudinis YC-9 was isolated from spring silt. The native enzyme was purified by ammonium sulfate precipitation, diethylaminoethyl-cellulose anion exchange chromatography, and Sephadex G-100 gel filtration. The purified β-1,3-1,4-glucanase was observed to be stable at 60 °C and retain more than 90% activity when incubated for 2 h at 60 °C and remain about 75% and 44% activity after incubating at 70 °C and 80 °C for 10 min, respectively. Acidity and temperature optimal for this enzyme was pH 6 and 65 °C. The open reading frame of the enzyme gene was measured to be 732 bp encoding 243 amino acids, with a predicted molecular weight of 27.47 kDa. The gene sequence of β-1,3-1,4-glucanase showed a homology of 98% with that of Bacillus licheniformis. After being expressed in E. coli BL21, active recombinant enzyme was detected both in the supernatants of the culture and the cell lysate, with the activity of 102.7 and 216.7 U/mL, respectively. The supernatants of the culture were used to purify the recombinant enzyme. The purified recombinant enzyme was characterized to show almost the same properties to the wild enzyme, except that the specific activity of the recombinant enzyme reached 5392.7 U/mg, which was higher than those ever reported β-1,3-1,4-glucanase from Bacillus strains. The thermal stability and high activity make this enzyme broad prospect for industry application. This is the first report on β-1,3-1,4-glucanase produced by B. altitudinis.

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 (&gt;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.

A food-grade industrial arming yeast expressing beta-1,3-1,4-glucanase with enhanced thermal stability

The aim of this work was to construct a novel food-grade industrial arming yeast displaying beta-1,3-1,4-glucanase and to evaluate the thermal stability of the glucanase for practical application. For this purpose, a bi-directional vector containing galactokinase (GAL1) and phosphoglycerate kinase 1 (PGK1) promoters in different orientations was constructed. The beta-1,3-1,4-glucanase gene from Bacillus subtilis was fused to alpha-agglutinin and expressed under the control of the GAL1 promoter. alpha-galactosidase induced by the constitutive PGK1 promoter was used as a food-grade selection marker. The feasibility of the alpha-galactosidase marker was confirmed by the growth of transformants harboring the constructed vector on a medium containing melibiose as a sole carbon source, and by the clear halo around the transformants in Congo-red plates owing to the expression of beta-1,3-1,4-glucanase. The analysis of beta-1,3-1,4-glucanase activity in cell pellets and in the supernatant of the recombinant yeast strain revealed that beta-1,3-1,4-glucanase was successfully displayed on the cell surface of the yeast. The displayed beta-1,3-1,4-glucanase activity in the recombinant yeast cells increased immediately after the addition of galactose and reached 45.1 U/ml after 32-h induction. The thermal stability of beta-1,3-1,4-glucanase displayed in the recombinant yeast cells was enhanced compared with the free enzyme. These results suggest that the constructed food-grade yeast has the potential to improve the brewing properties of beer.