Purification and characterization of a new xylanase with excellent stability from Aspergillus flavus and its application in hydrolyzing pretreated corncobs

Aqueous two-phase extraction and characterization of thermotolerant alkaliphilic Cladophora hutchinsiae xylanase: biochemical properties and potential applications in fruit juice clarification and fish feed supplementation

Xylanase finds extensive applications in diverse biotechnological fields such as biofuel production, pulp and paper industry, baking and brewing industry, food and feed industry, and deinking of waste paper. Here, polyethylene glycol (PEG)-phosphate aqueous two-phase system (ATPS) was applied for the purification of an alkaline active and thermotolerant xylanase from a marine source, Cladophora hutchinsiae (C. hutchinsiae). In the purification process, the effects of some experimental factors such as PEG concentration and PEG molar mass, potassium phosphate(K2HP04) concentration, and pH on xylanase distribution were systematically investigated. Relative enzymatic activity and purification factor obtained were 93.21% and 7.18, respectively. A single protein band of 28 kDa was observed on SDS-PAGE. The optimum temperature and pH of xylanase with beechwood xylan were 30 °C and 9.0, respectively. The Lineweaver-Burk graph was utilized to determine the Km (4.5 ± 0.8 mg/mL), Vmax (0.04 ± 0.01 U) and kcat (0.001 s-1) values of the enzyme. It was observed that the purified xylanase maintained 70% of its activity at 4 °C and was found stable at pH 4.0 by retaining almost all of its activity. Enzymatic activity was slightly enhanced with Na+, K+, Ca2+ and acetone. The highest increase in the reducing sugar amount was 53.6 ± 3.8, for orange juice at 50 U/mL enzyme concentration.

Expression and characterization of a protease-resistant β-d-fructofuranosidase BbFFase9 gene suitable for preparing invert sugars from soybean meal

A novel gene (BbFFase9), with an ORF of 1557 bp that encodes β-d-fructofuranosidase from Bifidobacteriaceae bacterium, was cloned and expressed in Escherichia coli. The recombinant protein (BbFFase9) was successfully purified and showed a single band with a molecular mass of 66.2 kDa. This was confirmed as a β-d-fructofuranosidase and exhibited a high specific activity of 209.2 U/mg. Although BbFFase9 was a soluble protein, it exhibited excellent tolerance to proteases such as pepsin, trypsin, acidic protease, neutral protease and Flavourzyme®, indicating its potential applicability in different fields. BbFFase9 exhibited typical invertase activity, and highly catalyzed the hydrolysis of the α1↔2β glycosidic linkage in molecules containing fructosyl moieties but with no detectable fructosyltransferase activity. It was optimally active at pH 6.5 and 50 °C and stable between pH 6.0 and 9.0 at a temperature of up to 45 °C for 30 min BbFFase9 could also effectively hydrolyze galacto-oligosaccharides, which are a flatulence factor in soybean meal, thus releasing new types of product such as melibiose and mannotriose, or degrading them into invert sugars, the sweeter fructose and glucose. This study is the first to report the application of this type of β-d-fructofuranosidase.

Quantification of Xylanolytic and Cellulolytic Activities of Fungal Strains Isolated from Palmaria palmata to Enhance R-Phycoerythrin Extraction of Palmaria palmata: From Seaweed to Seaweed

R-phycoerythrin (R-PE) can be enzymatically extracted from red seaweeds such as Palmaria palmata. This pigment has numerous applications and is notably known as an antioxidant, antitumoral or anti-inflammatory agent. Enzymes secreted by P. palmata associated fungal strains were assumed to be efficient and adapted for R-PE extraction from this macroalga. The aim of the present study was to quantify both xylanolytic and cellulolytic activities of enzymatic extracts obtained from six Palmaria palmata derived fungal strains. Degradation of P. palmata biomass by fungal enzymatic extracts was also investigated, focused on soluble protein and R-PE extraction. Enzymatic extracts were obtained by solid state fermentation. Macroalgal degradation abilities were evaluated by measuring reducing sugar release using DNS assays. Soluble proteins and R-PE recovery yields were evaluated through bicinchoninic acid and spectrophotometric assays, respectively. Various enzymatic activities were obtained according to fungal isolates up to 978 U/mL for xylanase and 50 U/mL for cellulase. Enzymatic extract allowed high degrading abilities, with four of the six fungal strains assessed exhibiting at least equal results as the commercial enzymes for the reducing sugar release. Similarly, all six strains allowed the same soluble protein extraction yield and four of them led to an improvement of R-PE extraction. R-PE extraction from P. palamata using marine fungal enzymes appeared particularly promising. To the best of our knowledge, this study is the first on the use of enzymes of P. palmata associated fungi in the degradation of its own biomass for biomolecules recovery.

A Strategy for Rapid Acquisition of the β-D-Fructofuranosidase Gene through Chemical Synthesis and New Function of Its Encoded Enzyme to Improve Gel Properties during Yogurt Processing

A chemical gene synthesis strategy was developed in order to obtain β-D-fructofuranosidase, and a novel gene, AlFFase3, was characterized from Aspergillus luchuensis and expressed in Escherichia coli. The recombinant protein was purified, showing a molecular mass of 68.0 kDa on SDS-PAGE, and displaying a specific activity towards sucrose of up to 771.2 U mg^-1, indicating its exceptional enzymatic capacity. AlFFase3 exhibited stability between pH 5.5 and 7.5, with maximal activity at pH 6.5 and 40 °C. Impressively, AlFFase3, as a soluble protein, was resistant to digestion by various common proteases, including Flavourzyme, acidic protease, pepsin, neutral protease, Proteinase K, alkaline proteinase, and trypsin. AlFFase3 also demonstrated significant transfructosylation activity, with a yield of various fructooligosaccharides up to 67%, higher than almost all other reports. Furthermore, we demonstrated that the addition of AlFFase3 enhanced the growth of probiotics in yogurt, thereby increasing its nutritional value. AlFFase3 also improved the formation of yogurt gel, reducing the gel formation time and lowering the elasticity while increasing its viscosity, thereby improving the palatability of yogurt and reducing production costs.

Efficient Degradation for Raffinose and Stachyose of a β-D-Fructofuranosidase and Its New Function to Improve Gel Properties of Coagulated Fermented-Soymilk

A novel β-D-fructofuranosidase gene was identified via database mining from Leptothrix cholodnii. The gene was chemically synthesized and expressed in Escherichia coli, resulting in the production of a highly efficient enzyme known as LcFFase1s. The enzyme exhibited optimal activity at pH 6.5 and a temperature of 50 °C while maintaining stability at pH 5.5-8.0 and a temperature below 50 °C. Furthermore, LcFFase1s exhibited remarkable resistance to commercial proteases and various metal ions that could interfere with its activity. This study also revealed a new hydrolysis function of LcFFase1s, which could completely hydrolyze 2% raffinose and stachyose within 8 h and 24 h, respectively, effectively reducing the flatulence factor in legumes. This discovery expands the potential applications of LcFFase1s. Additionally, the incorporation of LcFFase1s significantly reduced the particle size of coagulated fermented-soymilk gel, resulting in a smoother texture while maintaining the gel hardness and viscosity formed during fermentation. This represents the first report of β-D-fructofuranosidase enhancing coagulated fermented-soymilk gel properties, highlighting promising possibilities for future applications of LcFFase1s. Overall, the exceptional enzymatic properties and unique functions of LcFFase1s render it a valuable tool for numerous applications.

A multifaceted enzyme conspicuous in fruit juice clarification: An elaborate review on xylanase

Xylanase enzyme has been classified as an enzyme belonging to the glycoside hydrolase family. The catalytic action of xylanase is focused on the degradation of xylan, a substrate for this enzyme comprising of a complex arrangement of monosaccharides interlinked with the help of ester and glycosidic bonds. Xylan represents the second most profuse renewable polysaccharide present on earth. Breakage of the β- 1, 4-glycoside linkage in the xylan polymer is what makes xylanase enzyme an important biocatalyst favoring various applications including treatment of pulp for improving paper quality, improvement of bread quality, treatment of lignocelluloses waste, production of xylose sugar and production of biological fuels. Most recently, xylanase has been exploited in the food industry for the purpose of fruit juice clarification. Turbidity caused by the colloidal polysaccharides present in the freshly squeezed fruit juice poses a setback to the fruit juice industry since the commercial product must be clear and free of excess polysaccharides to improve juice quality and storage life. This review gives an overview of the recent advancements made in regards to xylanase enzyme being used commercially with main focus on its role in fruit juice clarification.

Bioprospecting of xylanase producing fungal strains: Multilocus phylogenetic analysis and enzyme activity profiling

The study aims to explore potential xylanase-producing indigenous fungi isolated from soil and vegetable wastes containing plant degraded matter, reporting multilocus phylogenetic analysis and xylanase enzyme activity from selective strains. Four potential xylanolytic fungi were identified through distinct primary and secondary screening of 294 isolates obtained from the samples. Morphological characterization and multigene analysis (ITS rDNA, 18S rDNA, LSU rDNA, β-tubulin, and actin gene) confirmed them as Aspergillus sp. AUMS56, Aspergillus tubingensis AUMS60 and AUMS64, and Aspergillus fumigatus AUKEMS24; achieving crude xylanase activities (through submerged fermentation using corn cobs) of 18.9, 32.29, 30.68, and 15.82 U ml^-1 , respectively. AUMS60 and AUMS64 (forming lineage with A. tubingensis and Aspergillus niger in the same phylogroup with 100% Bayesian posterior probability support) secreted single xylanase (Xyn60; 36 kDa) and multiple xylanases (Xyn64A and Xyn64B; 33.4 and 19.8 kDa) respectively, having pH optima of 6.0 and exhibiting maximal activity at 60°C. These enzymes were highly stable at 40°C (120 h) and retained more than 70% activity at 50°C and at pH 5-6 (upon 72 h incubation). Our analysis suggested these enzymes to be endoxylanases demonstrating substrate hydrolysis within 15 min of reaction and maximum efficiency of xylanases from AUMS60 and AUMS64 achieving 51.1% (13 h) and 52.2% (24 h) saccharification, respectively. They also showed enhanced catalytic activity with various cations. Based on our investigation on xylan hydrolysis, we believe that these xylanases may find significant industrial applications as they have a real potential of working as a bio-catalytic cocktail (patent file number: IN E1/38213/2020-DEL) for the enhanced saccharification of lignocelluloses.

Purification, Identification, and Characterization of a Glycoside Hydrolase Family 11-Xylanase with High Activity from Aspergillus niger VTCC 017

Xylanases (EC 3.2.1.8) have been considered as a potential green solution for the sustainable development of a wide range of industries including pulp and paper, food and beverages, animal feed, pharmaceuticals, and biofuels because they are the key enzymes that degrade the xylosidic linkages of xylan, the major component of the second most abundant raw material worldwide. Therefore, there is a critical need for the industrialized xylanases which must have high specific activity, be tolerant to organic solvent or detergent and be active during a wide range of conditions, such as high temperature and pH. In this study, an extracellular xylanase was purified from the culture broth of Aspergillus niger VTCC 017 for primary structure determination and properties characterization. The successive steps of purification comprised centrifugation, Sephadex G-100 filtration, and DEAE-Sephadex chromatography. The purified xylanase (specific activity reached 6596.79 UI/mg protein) was a monomer with a molecular weight of 37 kDa estimating from SDS electrophoresis. The results of LC/MS suggested that the purified protein is indeed an endo-1,4-β-D-xylanase. The purified xylanase showed the optimal temperature of 55 °C, and pH 6.5 with a stable xylanolytic activity within the temperature range of 45-50 °C, and within the pH range of 5.0-8.0. Most divalent metal cations including Zn²⁺, Fe²⁺, Mg²⁺, Cu²⁺, Mn²⁺ showed some inhibition of xylanase activity while the monovalent metal cations such as K⁺ and Ag⁺ exhibited slight stimulating effects on the enzyme activity. The introduction of 10-30% different organic solvents (n-butanol, acetone, isopropanol) and several detergents (Triton X-100, Tween 20, and SDS) slightly reduced the enzyme activity. Moreover, the purified xylanase seemed to be tolerant to methanol and ethanol and was even stimulated by Tween 80. Overall, with these distinctive properties, the putative xylanase could be a successful candidate for numerous industrial uses.

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.

Characterization of a novel GH10 xylanase with a carbohydrate binding module from Aspergillus sulphureus and its synergistic hydrolysis activity with cellulase

A study was carried out to investigate the characterization of a novel Aspergillus sulphureus JCM01963 xylanase (AS-xyn10A) with a carbohydrate binding module (CBM) and its application in degrading alkali pretreated corncob, rapeseed meal and corn stover alone and in combination with a commercial cellulase. In this study, the 3D structure of AS-xyn10A, which contained a CBM at C-terminal. AS-xyn10A and its CBM-truncated variant (AS-xyn10A-dC) was codon-optimized and over-expressed in Komagaella phaffii X-33 (syn. Pichia pastoris) and characterized with optimal condition at 70 °C and pH 5.0, respectively. AS-xyn10A displayed high activity to xylan extracted from corn stover, corncob, and rapeseed meal. The concentration of hydrolyzed xylo-oligosaccharides (XOSs) reached 1592.26 μg/mL, 1149.92 μg/mL, and 621.86 μg/mL, respectively. Xylobiose was the main product (~70%) in the hydrolysis mixture. AS-xyn10A significantly synergized with cellulase to improve the hydrolysis efficiency of corn stover, corncob, and rapeseed meal to glucose. The degree of synergy (DS) was 1.32, 1.31, and 1.30, respectively. Simultaneously, XOSs hydrolyzed with AS-xyn10A and cellulase was improved by 46.48%, 66.13% and 141.45%, respectively. In addition, CBM variant decreased the yields of xylo-oligosaccharide and glucose in rapeseed meal degradation. This study provided a novel GH10 endo-xylanase, which has potential applications in hydrolysis of biomass.

Biochemical characterization and enhanced production of endoxylanase from thermophilic mould Myceliophthora thermophila

Endoxylanase production from M. thermophila BJTLRMDU3 using rice straw was enhanced to 2.53-fold after optimization in solid state fermentation (SSF). Endoxylanase was purified to homogeneity employing ammonium sulfate precipitation followed by gel filtration chromatography and had a molecular mass of ~ 25 kDa estimated by SDS-PAGE. Optimal endoxylanase activity was recorded at pH 5.0 and 60 °C. Purified enzyme showed complete tolerance to n-hexane, but activity was slightly inhibited by other organic solvents. Among surfactants, Tweens (20, 60, and 80) and Triton X 100 slightly enhanced the enzyme activity. The V_max and K_m values for purified endoxylanase were 6.29 µmol/min/mg protein and 5.4 mg/ml, respectively. Endoxylanase released 79.08 and 42.95% higher reducing sugars and soluble proteins, respectively, which control after 48 h at 60 °C from poultry feed. Synergistic effect of endoxylanase (100 U/g) and phytase (15 U/g) on poultry feed released higher amount of reducing sugars (58.58 mg/feed), soluble proteins (42.48 mg/g feed), and inorganic phosphate (28.34 mg/feed) in contrast to control having 23.55, 16.98, and 10.46 mg/feed of reducing sugars, soluble proteins, and inorganic phosphate, respectively, at 60 °C supplemented with endoxylanase only.

Enhanced xylanase and endoglucanase production from Beauveria bassiana SAN01, an entomopathogenic fungal endophyte

This study was undertaken to explore alternative applications of the widely known entomopathogenic/endophytic fungus, Beauveria bassiana, besides its sole use as a biocontrol agent. B. bassiana SAN01, was investigated for the production of two glycoside hydrolases, xylanase and endoglucanase under submerged conditions. Among the different biomass tested, wheat bran provided the best results for both xylanase and endoglucanase, and their production levels were further enhanced using response surface methodology. Under optimised conditions, heightened yields of 1061 U/ml and 23.03 U/ml were observed for xylanase and endoglucanase, respectively, which were 3.44 and 1.35 folds higher than their initial yields. These are the highest ever production levels reported for xylanase and endoglucanase from any B. bassiana strain or any known entomopathogenic fungi. Furthermore, the efficacy of xylanase/endoglucanase cocktail in the saccharification of sugarcane bagasse was evaluated. The highest amount of reducing sugar released from the pretreated biomass by the action of the crude Beauveria enzyme cocktail was recorded at 30°C after 8 h incubation. The significant activities of the hydrolytic enzymes recorded with B. bassiana in this study thus present promising avenues for the use of the entomopathogen as a new source of industrial enzymes and by extension, other biotechnological applications.

Production, characteristics, and biotechnological applications of microbial xylanases

Microbial xylanases have gathered great attention due to their biotechnological potential at industrial scale for many processes. A variety of lignocellulosic materials, such as sugarcane bagasse, rice straw, rice bran, wheat straw, wheat bran, corn cob, and ragi bran, are used for xylanase production which also solved the great issue of solid waste management. Both solid-state and submerged fermentation have been used for xylanase production controlled by various physical and nutritional parameters. Majority of xylanases have optimum pH in the range of 4.0-9.0 with optimum temperature at 30-60 °C. For biochemical, molecular studies and also for successful application in industries, purification and characterization of xylanase have been carried out using various appropriate techniques. Cloning and genetic engineering are used for commercial-level production of xylanase, to meet specific economic viability and industrial needs. Microbial xylanases are used in various biotechnological applications like biofuel production, pulp and paper industry, baking and brewing industry, food and feed industry, and deinking of waste paper. This review describes production, characteristics, and biotechnological applications of microbial xylanases.

A detailed overview of xylanases: an emerging biomolecule for current and future prospective

Xylan is the second most abundant naturally occurring renewable polysaccharide available on earth. It is a complex heteropolysaccharide consisting of different monosaccharides such as l-arabinose, d-galactose, d-mannoses and organic acids such as acetic acid, ferulic acid, glucuronic acid interwoven together with help of glycosidic and ester bonds. The breakdown of xylan is restricted due to its heterogeneous nature and it can be overcome by xylanases which are capable of cleaving the heterogeneous β-1,4-glycoside linkage. Xylanases are abundantly present in nature (e.g., molluscs, insects and microorganisms) and several microorganisms such as bacteria, fungi, yeast, and algae are used extensively for its production. Microbial xylanases show varying substrate specificities and biochemical properties which makes it suitable for various applications in industrial and biotechnological sectors. The suitability of xylanases for its application in food and feed, paper and pulp, textile, pharmaceuticals, and lignocellulosic biorefinery has led to an increase in demand of xylanases globally. The present review gives an insight of using microbial xylanases as an “Emerging Green Tool” along with its current status and future prospective.

Purification and characterization of a novel -glucosidase from Aspergillus flavus and its application in saccharification of soybean meal

Aspergillus flavus has been regarded as a potential candidate for its production of industrial enzymes, but the details of β-glucosidase from this strain is very limited. In herein, we first reported a novel β-glucosidase (AfBglA) with the molecular mass of 94.2 kDa from A. flavus. AfBglA was optimally active at pH 4.5 and 60 °C and is stable between pH 3.5 and 9.0 and at a temperature of up to 55 °C for 30 min remaining more than 90% of its initial activity. It showed an excellent tolerance to Trypsin, Pepsin, Compound Protease, and Flavourzyme and its activity was not inhibited by specific certain cations. AfBglA displayed broad substrate specificity, it acted on all tested pNP-glycosides and barley glucan, indicating this novel β-glucosidase exhibited a β-1, 3-1, 4-glucanase activity. Moreover, the AfBglA could effectively hydrolyze the soybean meal suspension into glucose and exhibit a strong tolerance to the inhibition of glucose at a concentration of 20.0 g/L during the saccharification. The maximum amount of the glucose obtained by AfBglA corresponded to 67.0 g/kg soybean meal. All of these properties mentioned above indicated that the AfBglA possibly attractive for food and feed industry and saccharification of cellulolytic materials.