Cloning, expression and characterization of a thermo-alkali-stable xylanase from Aspergillus oryzae LC1 in Escherichia coli BL21(DE3)

Advances of microbial xylanases in the application of flour industries: A comprehensive review

Microbial xylanase has a wide range of applications, and many researchers favoring its utilization as an alternative to improve flour products. Wheat flour is the main raw material of flour products, although the content of arabinoxylan is not high in flour products, but it has a great influence on the quality of flour products, microbial xylanase can act on wheat arabinoxylan, so as to play the role of flour product improvement. This review carries out a description of the research progress on the application of xylanases in flour products in terms of xylanase properties, different families of xylanases and improvement mechanisms of xylanases in flour products. According to the properties of various microbial sources of xylanases, the suitable xylanase can be added to flour products, and the effect of xylanase towards wheat arabinoxylan in flour can be used to improve the quality of flour products. The molecular modification based on the properties of xylanase and the crystal structure of different families of xylanase and their substrate specificity toward wheat arabinoxylan are discussed. The article reviews the information about microbial xylanases in order to achieve better results in flour products and to provide a theoretical basis for their industrial application.

The postbiotic potential of Aspergillus oryzae - a narrative review

The filamentous fungus Aspergillus oryzae has a long tradition in East Asian food processing. It is therefore not surprising that in recent years fermentation products of A. oryzae have attracted attention in the emerging field of postbiotics. This review aims to provide a comprehensive summary of the potential postbiotic effects of fermentation products from A. oryzae, by discussing possible mechanisms of action against the background of the molecular composition determined so far. In particular, cell wall constituents, enzymes, extracellular polymeric substances, and various metabolites found in A. oryzae fermentation preparations are described in detail. With reference to the generally assumed key targets of postbiotics, their putative beneficial bioactivities in modulating the microbiota, improving epithelial barrier function, influencing immune responses, metabolic reactions and signaling through the nervous system are assessed. Drawing on existing literature and case studies, we highlight A. oryzae as a promising source of postbiotics, particularly in the context of animal health and nutrition. Challenges and opportunities in quality control are also addressed, with a focus on the necessity for standardized methods to fully harness the potential of fungal-based postbiotics. Overall, this article sheds light on the emerging field of A. oryzae-derived postbiotics and emphasizes the need for further research to fully realize their therapeutic potential.

A new halotolerant xylanase from Aspergillus clavatus expressed in Escherichia coli with catalytic efficiency improved by site-directed mutagenesis

Daily agro-industrial waste, primarily cellulose, lignin, and hemicellulose, poses a significant environmental challenge. Harnessing lignocellulolytic enzymes, particularly endo-1,4-β-xylanases, for efficient saccharification is a cost-effective strategy, transforming biomass into high-value products. This study focuses on the cloning, expression, site-directed mutagenesis, purification, three-dimensional modeling, and characterization of the recombinant endo-1,4-β-xylanase (XlnA) from Aspergillus clavatus in Escherichia coli. This work includes evaluation of the stability at varied NaCl concentrations, determining kinetic constants, and presenting the heterologous expression of XlnAΔ36 using pET22b(+). The expression led to purified enzymes with robust stability across diverse pH levels, exceptional thermostability at 50 °C, and 96-100% relative stability after 24 h in 3.0 M NaCl. Three-dimensional modeling reveals a GH11 architecture with catalytic residues Glu 132 and 22. XlnAΔ36 demonstrates outstanding kinetic parameters compared to other endo-1,4-β-xylanases, indicating its potential for industrial enzymatic cocktails, enhancing saccharification. Moreover, its ability to yield high-value compounds, such as sugars, suggests a promising and ecologically positive alternative for the food and biotechnology industries.

Gene cloning, expression, and characterization of two endo-xylanases from Bacillus velezensis and Streptomyces rochei, and their application in xylooligosaccharide production

Endo-xylanase hydrolyzing xylan in cellulosic residues releasing xylobiose as the major product at neutral pH are desirable in the substitute sweeteners industry. In this study, two endo-xylanases were obtained from Streptomyces rochei and Bacillus velezensis. SrocXyn10 showed the highest identity of 77.22%, with a reported endo-xylanase. The optimum reaction temperature and pH of rSrocXyn10-Ec were pH 7.0 and 60°C, with remarkable stability at 45°C or pHs ranging from 4.5 to 11.0. rBvelXyn11-Ec was most active at pH 6.0 and 50°C, and was stable at 35°C or pH 3.5 to 10.5. Both rSrocXyn10-Ec and rBvelXyn11-Ec showed specific enzyme activities on wheat arabinoxylan (685.83 ± 13.82 and 2809.89 ± 21.26 U/mg, respectively), with no enzyme activity on non-xylan substrates. The Vmax of rSrocXyn10-Ec and rBvelXyn11-Ec were 467.86 U mg-1 and 3067.68 U mg-1, respectively. The determined Km values of rSrocXyn10-Ec and rBvelXyn11-Ec were 3.08 g L-1 and 1.45 g L-1, respectively. The predominant product of the hydrolysis of alkaline extracts from bagasse, corncob, and bamboo by rSrocXyn10-Ec and rBvelXyn11-Ec were xylooligosaccharides. Interestingly, the xylobiose content in hydrolysates by rSrocXyn10-Ec was approximately 80%, which is higher than most reported endo-xylanases. rSrocXyn10-Ec and rBvelXyn11-Ec could be excellent candidates to produce xylooligosaccharides at neutral/near-neutral pHs. rSrocXyn10-Ec also has potential value in the production of xylobiose as a substitute sweetener.

Cloning, Expression, and Characterization of a GHF 11 Xylanase from Alteromonas macleodii HY35 in Escherichia coli

A xylanase gene xynZT-1 from Alteromonas macleodii HY35 was cloned and expressed in Escherichia coli (E. coli). The sequencing results showed that the ORF of xynZT-1 was 831 bp. The xylanase DNA sequence encoded a 29 amino acids (aa) signal peptide and a 247-aa mature peptide. The XynZT-1 has been a calculated molecular weight (MW) of 27.93 kDa, isoelectric point (pI) of 5.11 and the formula C₁₂₆₆H₁₈₂₉N₃₂₇O₃₈₄S₅. The amino acid sequence of the xynZT-1 had a high similarity with that of glycosyl hydrolase family 11 (GHF11) reported from other microorganisms. The DNA sequence encoding mature peptide was subcloned into pET-28a(+) expression vector. The resulted plasmid pET-28a-xynZT-1 was transformed into E. coli BL21(DE3), and the recombinant strain BL21(DE3)/xynZT-1 was obtained. The optimum temperature and pH of the recombinant XynZT-1 were 45 ℃ and 5.0, respectively.

Safe production of Aspergillus terreus xylanase from Ricinus communis: gene identification, molecular docking, characterization, production of xylooligosaccharides, and its biological activities

BACKGROUND

The production of industrial enzymes such as xylanase using sufficient cost-effective substrates from potent microorganisms is considered economically feasible. Studies have reported castor cake (Ricinus communis) as the most potent and inexpensive alternative carbon source for production of xylanase C by using Aspergillus terreus (A. terreus).

RESULTS

A. terreus strain RGS Eg-NRC, a local isolate from agro-wastes, was first identified by sequencing the internal transcribed spacer region of a nuclear DNA encoding gene cluster deposited in GenBank (accession number MW282328). Before optimization of xylanase production, A. terreus produced 20.23 U/g of xylanase after 7 days using castor cake as a substrate in a solid-state fermentation (SSF) system that was employed to achieve ricin detoxification and stimulate xylanase production. Physicochemical parameters for the production of xylanase were optimized by using a one-variable-at-a-time approach and two statistical methods (two-level Plackett-Burman design and central composite design, CCD). The maximum xylanase yield after optimization was increased by 12.1-fold (245 U/g). A 60-70% saturation of ammonium sulfate resulted in partially purified xylanase with a specific activity of 3.9 IU/mg protein. At 60 °C and pH 6, the partially purified xylanase had the highest activity, and the activation energy (Ea) was 23.919 kJmol. Subsequently, antioxidant capacity and cytotoxicity tests in normal Ehrlich ascites carcinoma human cells demonstrated xylooligosaccharides produced by the xylanase degradation of xylan as a potent antioxidant and moderate antitumor agent. Further investigations with sodium dodecyl sulfate polyacrylamide gel electrophoresis then determined the molecular weight of partially purified xylanase C to be 36 kDa. Based on the conserved regions, observations revealed that xylanase C belonged to the glycosyl hydrolase family 10. Next, the xylanase-encoding gene (xynC), which has an open reading frame of 981 bp and encodes a protein with 326 amino acids, was isolated, sequenced, and submitted to the NCBI GenBank database (accession number LC595779.1). Molecular docking analysis finally revealed that Glu156, Glu262, and Lys75 residues were involved in the substrate-binding and protein-ligand interaction site of modeled xylanase, with a binding affinity of -8.7 kcal. mol^-1. CONCLUSION: The high production of safe and efficient xylanase could be achieved using economical materials such as Ricinus communis.

Exploring competitive inhibition of a family 10 xylanase derived from Hu sheep rumen microbiota by Oryza sativa xylanase inhibitor protein: In vitro and in silico perspectives

The catalytic domain of family GH10 xylanase, XYN-LXY_CD derived from Hu sheep rumen microbiota was expressed in Pichia pastoris X33. The special activity of reXYN-LXY_CD in the culture supernatant was 232.56 U/mg. The optima of reXYN-LXY_CD were 53 °C and pH 7.0. Recombinant Oryza sativa xylanase inhibitor protein (rePOsXIP) competitively inhibited reXYN-LXY_CD with an inhibition constant (K_i) value of 237.37 nM. The concentration of hydrolysates released from beechwood xylan by reXYN-LXY_CD reduced when rePOsXIP was added into the hydrolytic system. Fluorescence of reXYN-LXY_CD was statically quenched by rePOsXIP in a dose-dependent manner. The details in intermolecular interaction between XYN-LXY_CD and OsXIP were investigated by using molecular dynamics (MD) simulations, binding free energy computation and non-covalent interactions (NCI) analysis. Hydrogen bonding and van der Waals played indispensable roles in the XYN-LXY_CD/OsXIP interaction. The α-7 helix of OsXIP tightly occupied the catalytic pocket of XYN-LXY_CD with hydrogen bonding such as K239_OsXIP-N261/Q292/E197_{XYN-LXY_CD} (E197, the acid-base catalytic residue), D236_OsXIP-K327_{XYN-LXY_CD} and Q242_OsXIP-E211/Q212_{XYN-LXY_CD}. Based on the quantum theory of atoms in molecules (QTAIM), the Laplacian of electron density and core-valence bifurcation index of HZ3_K239-OE2_E197 were 0.1025 a.u. and 0.002218, respectively. Elucidating the mechanism underlying xylanase-inhibitor interactions might help construct XYN-LXY_CD mutants that gain resistance to XIPs and high catalytic activity, which would be more efficient in feed additives in livestock.

Recent Developments in Industrial Mycozymes: A Current Appraisal

Fungi, being natural decomposers, are the most potent, ubiquitous and versatile sources of industrial enzymes. About 60% of market share of industrial enzymes is sourced from filamentous fungi and yeasts. Mycozymes (myco-fungus; zymes-enzymes) are playing a pivotal role in several industrial applications and a number of potential applications are in the offing. The field of mycozyme production, while maintaining the old traditional methods, has also witnessed a sea change due to advents in recombinant DNA technology, optimisation protocols, fermentation technology and systems biology. Consolidated bioprocessing of abundant lignocellulosic biomass and complex polysaccharides is being explored at an unprecedented pace and a number of mycozymes of diverse fungal origins are being explored using suitable platforms. The present review attempts to revisit the current status of various mycozymes, screening and production strategies and applications thereof.

Beauveria bassiana Xylanase: Characterization and Wastepaper Deinking Potential of a Novel Glycosyl Hydrolase from an Endophytic Fungal Entomopathogen

Beauveria bassiana is an entomopathogenic fungus widely used as a biopesticide for insect control; it has also been shown to exist as an endophyte, promoting plant growth in many instances. This study highlights an alternative potential of the fungus; in the production of an industrially important biocatalyst, xylanase. In this regard, Beauveria bassiana SAN01 xylanase was purified to homogeneity and subsequently characterized. The purified xylanase was found to have a specific activity of 324.2 U·mg⁻¹ and an estimated molecular mass of ~37 kDa. In addition, it demonstrated optimal activity at pH 6.0 and 45 °C while obeying Michaelis–Menton kinetics towards beechwood xylan with apparent K_m, V_max and k_cat of 1.98 mg·mL⁻¹, 6.65 μM·min⁻¹ and 0.62 s⁻¹ respectively. The enzyme activity was strongly inhibited by Ag²⁺ and Fe³⁺ while it was significantly enhanced by Co²⁺ and Mg²⁺. Furthermore, the xylanase was shown to effectively deink wastepaper at an optimal rate of 106.72% through its enzymatic disassociation of the fiber-ink bonds as demonstrated by scanning electron microscopy and infrared spectroscopy. This is the first study to demonstrate the biotechnological application of a homogeneously purified glycosyl hydrolase from B. bassiana.

Optimization of β-1,4-Endoxylanase Production by an Aspergillus niger Strain Growing on Wheat Straw and Application in Xylooligosaccharides Production

Plant biomass constitutes the main source of renewable carbon on the planet. Its valorization has traditionally been focused on the use of cellulose, although hemicellulose is the second most abundant group of polysaccharides on Earth. The main enzymes involved in plant biomass degradation are glycosyl hydrolases, and filamentous fungi are good producers of these enzymes. In this study, a new strain of Aspergillus niger was used for hemicellulase production under solid-state fermentation using wheat straw as single-carbon source. Physicochemical parameters for the production of an endoxylanase were optimized by using a One-Factor-at-a-Time (OFAT) approach and response surface methodology (RSM). Maximum xylanase yield after RSM optimization was increased 3-fold, and 1.41- fold purification was achieved after ultrafiltration and ion-exchange chromatography, with about 6.2% yield. The highest activity of the purified xylanase was observed at 50 °C and pH 6. The enzyme displayed high thermal and pH stability, with more than 90% residual activity between pH 3.0–9.0 and between 30–40 °C, after 24 h of incubation, with half-lives of 30 min at 50 and 60 °C. The enzyme was mostly active against wheat arabinoxylan, and its kinetic parameters were analyzed (K_m = 26.06 mg·mL⁻¹ and V_max = 5.647 U·mg⁻¹). Wheat straw xylan hydrolysis with the purified β-1,4 endoxylanase showed that it was able to release xylooligosaccharides, making it suitable for different applications in food technology.

Optimization and bioactivity verification of porcine recombinant visfatin with high expression and low endotoxin content using pig liver as template

In order to obtain the porcine recombinant visfatin protein with high expression and low endotoxin content, the current study aims to express and verify the biological activity of the purified porcine recombinant visfatin protein. Firstly, four different expression strains were successfully constructed. Then they were simultaneously induced at 37 °C for 4 h and 16 °C for 16 h. The results showed that Visfatin-pET28a-Transetta was the best strain with high protein expression and purity at 16 °C induction for 16 h. After that, endotoxin was reduced from the recombinant visfatin until the residual endotoxin was less than one endotoxin units per milliliter (EU/mL). Finally, the purified porcine recombinant visfatin protein was incubated with RAW264.7 cells. The results of cell counting kit-8 (CCK-8) showed the survival rate of the cells first increased and then decreased with the increase in visfatin concentration. When the concentration of visfatin was 700 ng/mL, the survival rate of the cells was the highest. Thereafter, control (PBS), Visfatin and Visfatin + PolymyxinB (Ploy.B) groups were incubated with the RAW264.7 cells for 6 h. Real-time quantitative polymerase chain reaction (RT-qPCR) and Enzyme Linked Immuno-Sorbent Assay (ELISA) results showed that, as compared to the control group, the expressions of interleukin (IL)-1β, tumor necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1 in Visfatin group were significantly increased (P < 0.05). However, there was no significant difference between the Visfatin and Visfatin + Poly.B groups, indicating that porcine recombinant visfatin protein promoted the inflammatory activity of RAW264.7 cells while the residual endotoxin did not play a role, suggesting biological activity of porcine recombinant visfatin protein.

A thermophilic and thermostable xylanase from Caldicoprobacter algeriensis: Recombinant expression, characterization and application in paper biobleaching

A novel xylanase gene xynBCA, encoding a polypeptide of 439 residues (XynBCA), was cloned from Caldicoprobacter algeriensis genome and recombinantly expressed in Escherichia coli BL21(DE3). The amino acid sequence analysis showed that XynBCA belongs to the glycoside hydrolase family 10. The purified recombinant enzyme has a monomeric structure of 52 kDa. It is active and stable in a wide range of pH from 3 to 10 with a maximum activity at 6.5. Interestingly, XynBCA was highly thermoactive with an optimum temperature of 80 °C, thermostable with a half-life of 20 min at 80 °C. The specific activity was 117 U mg^-1, while the K_m and V_max were 1.247 mg ml^-1, and 114.7 μmol min^-1 mg^-1, respectively. The investigation of XynBCA in kraft pulp biobleaching experiments showed effectiveness in releasing reducing sugars and chromophores, with best achievements at 100 U g^-1 of pulp and 1 h of incubation. The comparative molecular modeling studies with the less thermostable Xylanase B from Clostridium stercorarium, revealed extra charged residues at the surface of XynBCA potentially participating in the formation of intermolecular hydrogen bonds with solvent molecules or generating salt bridges, therefore contributing to the higher thermal stability.

N-Terminal Fused Signal Peptide Prompted Extracellular Production of a Bacillus-Derived Alkaline and Thermo Stable Xylanase in E. coli Through Cell Autolysis

Xylanases are extensively used as industrial enzymes for its ability of hydrolyzing xylan to oligosaccharides. Here, XynHB, a thermo and alkaline stable xylanase derived from Bacillus pumilus HBP8, was extracellularly produced in E. coli cells through N-terminal-fused signal peptides. We found that the matured XynHB itself could be auto-secreted out of E. coli BL21(DE3) cells at a very low level, and two Sec-pathway signal peptides, PelB and OmpA, and one dual Sec-Tat-pathway signal peptide, FhuD, could effectively prompt its extracellular production up to 12-fold. Our results showed that PelB signal peptide led to the highest extracellular production of XynHB for approximately 54.1 μg/mL, and FhuD-fused XynHB possessed the highest specific activity of 1746.0 U/mg at 70 °C. Meanwhile, our studies also indicated that PelB- and FhuD-fused XynHB might disrupt E. coli cells' periplasm during their secretion process, thus causing cell lysis to facilitate their extracellular production. Moreover, further characterization revealed that the extracellular production of XynHB was not affected by the outer membrane permeability of E. coli cells. Our studies provided an advantageous strategy for the extracellular production of xylanase in E. coli, which may also be used for E. coli autolysis in the future.