Production and characterization of a novel acidophilic and thermostable xylanase from Thermoascus aurantiacu

Investigation of the enzymatic characteristics of thermotolerant xylanase McXyn0243 derived from Malbranchea cinnamomea, and its application in the degradation of three agricultural residues for the production of xylooligosaccharides

Malbranchea cinnamomea produces enzymes essential for degrading lignocellulosic materials, converting agricultural waste into high-value compounds like xylooligosaccharides (XOSs). In this study, we cloned and expressed an endo-1,4-β-xylanase, McXyn0243, from M. cinnamomea and investigated its enzymatic properties and application in agricultural wastes degradation. The cDNA of McXyn0243 (675 bp) encodes a 24.4 kDa glycoside hydrolase family 11 enzyme with optimal activity at pH 7.5 and 70 °C. McXyn0243 also demonstrated broad stability across a wide range of pH and temperatures. It showed higher activity on alcohol-insoluble xylan than water-insoluble xylan, with the highest specific activity (2163.2 U/mg) observed when rice husk alcohol-insoluble xylan was used. Kinetic parameters for beechwood xylan were Km = 8.6 ± 0.3 mg/mL, kcat = 26,212.5 s-1, and kcat/Km = 3048.0 mL/mg/s. McXyn0243 degraded xylotriose to xylobiose but not xylobiose, with xylotriose and xylobiose as the main products from xylotetraose, xylopentaose, and xylohexaose. Coupled with autohydrolysis, McXyn0243 produced XOSs yields of 123.3 ± 1.9 mg/g, 222.4 ± 1.3 mg/g, and 150.1 ± 0.9 mg/g from rice husk, corn cob, and wheat bran, with xylobiose and xylotriose as the main components.

Expression and characterization of a novel halophilic GH10 β-1,4-xylanase from Trichoderma asperellum ND-1 and its synergism with a commercial α-L-arabinofuranosidase on arabinoxylan degradation

Enzymatic hydrolysis of arabinoxylan is of cost-effective strategy to yield valuable macromolecules, e.g., xylooligosaccharides (XOS). A novel halophilic GH10 xylanase (TaXYL10) from Trichoderma asperellum ND-1 was over-expressed in Pichia pastoris and migrated as a single band (~36 kDa) in SDS-PAGE. TaXYL10 displayed >80 % activity in the presence of 4.28 M NaCl and 10 % ethanol. Moreover, TaXYL10 exhibited optimal activity at pH 6.0 and 55 °C, and remarkable pH stability (>80 % activity at pH 4.0-6.0). K+ and Al3+ could remarkably promote TaXYL10 activity, while the presence of 10 mM Fe2+, Zn2+, Cu2+ and Fe3+ decreased its activity. TaXYL10 possesses the highest catalytic activity towards beechwood xylan. TLC analysis revealed that it could rapidly degrade xylan and XOS with DP ≥ 3, yielding xylotriose and xylobiose. Site-directed mutagenesis indicated that Glu154 and Glu259 are crucial active residues for TaXYL10, while Asp295 and Glu69 played auxiliary roles in xylan hydrolysis. Additionally, TaXYL10 acted cooperatively with a commercial α-L-arabinofuranosidase (AnAra) towards arabinoxylan degradation (583.5 μg/mL), a greater synergy degree of 1.79 was obtained after optimizing enzymatic ratios. This work not only expands the diversity of Trichoderma GH10 xylanases, but also reveals the promising potential of TaXYL10 in various industrial applications.

Production and characterization of acidophilic xylanase from wood degrading white rot fungus by solid-state fermentation of wheat straw

Xylanases (EC 3.2.1.8) catalyze the breakdown of xylan, which is the second most abundant polysaccharide in plant cell walls. Biological catalysts have gained greater global attention than chemical catalysts in different industrial processes because they are highly selective, easy to control and have a negligible environmental impact. The aim of this study was to investigate the xylanolytic potential of white-rot fungi, optimize their physicochemical conditions and characterize the resulting xylanase. Sixty-eight white-rot fungus (WRF) isolates were screened for their xylanolytic potential and growth conditions for maximal xylanase production using cheap agricultural residue (wheat straw) as the sole carbon source. Five WRF isolates with high xylanase yields (73.63 ± 0.0283-63.6 ± 0.01247 U/ml) were selected by qualitative and quantitative screening methods. The optimum xylanase production occurred at pH 5.0 and 28 °C. Solid-state fermentation (SSF) yielded a high amount of xylanase. The highest xylanase activity (80.9-61.274 U/mL) was recorded in the pH range of 5.0-6.5 and at 50 °C. The metal ions Mg2+, Ca2+ and Mn2+ enhanced the activity of xylanase (127.28-110.06 %), while Cu2+, Fe2+ and K+ inhibited the activity with 43.4-17 % losses. The km and Vmax were 0.32-0.545 mg/mL and 86.95-113.63 μmol/min/mg, respectively. This finding indicates that wheat straw can be used for large-scale xylanase production under SSF conditions. The pH and temperature profiles and stabilities indicate that the xylanase produced in the present study can be applied in food and animal feed industries.

Purification, biochemical characterization, and biotechnological applications of a multifunctional enzyme from the Thermoascus aurantiacus PI3S3 strain

The filamentous Thermoascus aurantiacus fungus characterized by its thermophilic nature, is recognized as an exceptional producer of various enzymes with biotechnological applications. This study aimed to explore biotechnological applications using polygalacturonase (PG) derived from the Thermoascus aurantiacus PI3S3 strain. PG production was achieved through submerged fermentation and subsequent purification via ion-exchange chromatography and gel filtration methods. The crude extract exhibited a diverse spectrum of enzymatic activities including amylase, cellulase, invertase, pectinase, and xylanase. Notably, it demonstrated the ability to hydrolyze sugarcane bagasse biomass, corn residue, and animal feed. The purified PG had a molecular mass of 36 kDa, with optimal activity observed at pH 4.5 and 70 °C. The activation energy (Ea) was calculated as 0.513 kJ mol-1, highlighting activation in the presence of Ca2+. Additionally, it displayed apparent Km, Vmax, and Kcat values of at 0.19 mg mL-1, 273.10 U mL-1, and 168.52 s-1, respectively, for hydrolyzing polygalacturonic acid. This multifunctional PG exhibited activities such as denim biopolishing, apple juice clarification, and demonstrated both endo- and exo-polygalacturonase activities. Furthermore, it displayed versatility by hydrolyzing polygalacturonic acid, carboxymethylcellulose, and xylan. The T. aurantiacus PI3S3 multifunctional polygalacturonase showed heightened activity under acidic pH, elevated temperatures, and in the presence of calcium. Its multifunctional nature distinguished it from other PGs, significantly expanding its potential for diverse biotechnological applications.

Transformation of corncob into high-value xylooligosaccharides using glycoside hydrolase families 10 and 11 xylanases from Trichoderma asperellum ND-1

Effective production of xylooligosaccharides (XOS) with lower proportion of xylose entails unique and robust xylanases. In this study, two novel xylanases from Trichoderma asperellum ND-1 belonging to glycoside hydrolase families 10 (XynTR10) and 11 (XynTR11) were over-expressed in Komagataella phaffii X-33 and characterized to be robust enzymes with high halotolerance and ethanol tolerant. Both enzymes displayed strict substrate specificity towards beechwood xylan and wheat arabinoxylan. (Glu153/Glu258) and (Glu161/Glu252) were key catalytic sites for XynTR10 and XynTR11. Notably, XynTR11 could rapidly degrade xylan/XOS into xylobiose without xylose via transglycosylation. Direct degradation of corncob using XynTR10 and XynTR111 displayed that while XynTR10 yielded 77% xylobiose and 25% xylose, XynTR11 yielded much less xylose (11%) and comparable amounts of xylobiose (63%). XynTR10 or XynTR111 has great potential as a catalyst for bioconversion of xylan-containing agricultural waste into high-value products (biofuel or XOS), which is of significant benefit for the economy and environment.

Biochemical characterization of a novel acidophilic β-xylanase from Trichoderma asperellum ND-1 and its synergistic hydrolysis of beechwood xylan

Acidophilic β-xylanases have attracted considerable attention due to their excellent activity under extreme acidic environments and potential industrial utilizations. In this study, a novel β-xylanase gene (Xyl11) of glycoside hydrolase family 11, was cloned from Trichoderma asperellum ND-1 and efficiently expressed in Pichia pastoris (a 2.0-fold increase). Xyl11 displayed a maximum activity of 121.99 U/ml at pH 3.0 and 50°C, and exhibited strict substrate specificity toward beechwood xylan (K_m = 9.06 mg/ml, V_max = 608.65 μmol/min/mg). The Xyl11 retained over 80% activity at pH 2.0–5.0 after pretreatment at 4°C for 1 h. Analysis of the hydrolytic pattern revealed that Xyl11 could rapidly convert xylan to xylobiose via hydrolysis activity as well as transglycosylation. Moreover, the results of site-directed mutagenesis suggested that the Xyl11 residues, Glu¹²⁷, Glu¹⁶⁴, and Glu²¹⁶, are essential catalytic sites, with Asp¹³⁸ having an auxiliary function. Additionally, a high degree of synergy (15.02) was observed when Xyl11 was used in association with commercial β-xylosidase. This study provided a novel acidophilic β-xylanase that exhibits excellent characteristics and can, therefore, be considered a suitable candidate for extensive applications, especially in food and animal feed industries.

Thermostable Cellulases / Xylanases From Thermophilic and Hyperthermophilic Microorganisms: Current Perspective

The bioconversion of lignocellulose into monosaccharides is critical for ensuring the continual manufacturing of biofuels and value-added bioproducts. Enzymatic degradation, which has a high yield, low energy consumption, and enhanced selectivity, could be the most efficient and environmentally friendly technique for converting complex lignocellulose polymers to fermentable monosaccharides, and it is expected to make cellulases and xylanases the most demanded industrial enzymes. The widespread nature of thermophilic microorganisms allows them to proliferate on a variety of substrates and release substantial quantities of cellulases and xylanases, which makes them a great source of thermostable enzymes. The most significant breakthrough of lignocellulolytic enzymes lies in lignocellulose-deconstruction by enzymatic depolymerization of holocellulose into simple monosaccharides. However, commercially valuable thermostable cellulases and xylanases are challenging to produce in high enough quantities. Thus, the present review aims at giving an overview of the most recent thermostable cellulases and xylanases isolated from thermophilic and hyperthermophilic microbes. The emphasis is on recent advancements in manufacturing these enzymes in other mesophilic host and enhancement of catalytic activity as well as thermostability of thermophilic cellulases and xylanases, using genetic engineering as a promising and efficient technology for its economic production. Additionally, the biotechnological applications of thermostable cellulases and xylanases of thermophiles were also discussed.

Identification and characterization of a thermostable GH11 xylanase from Paenibacillus campinasensis NTU-11 and the distinct roles of its carbohydrate-binding domain and linker sequence

An extracellular thermostable xylanase (XynNTU) from Paenibacillus campinasensis NTU-11, consisted of a glycoside hydrolase (GH) family 11 catalytic domain, a Gly/Pro-rich linker sequence (LS) and a family 6 carbohydrate-binding module (CBM6), was identified and expressed in E. coli BL21. The purified XynNTU had a specific activity of 2750 U/mg and an optimal activity at 60 °C and pH 7.0, and retained a residual activity of 58.4% after incubation (60 °C, 48 h). Two truncated mutants, CBM6-truncated form XynNTU-CDLS, CBM6 and linker-truncated form XynNTU-CD, possessed similar values of optimum pH and temperature as the native XynNTU. XynNTU-CD displayed a lower thermostability than XynNTU, whereas for XynNTU-CDLS, more than 90% of residual activity was remained (60 °C, 48 h), indicating that this enzyme presented a higher thermostability than that of the majority of reported GH11 xylanases. Furthermore, XynNTU and two mutants maintained more than 70% of residual activity at pH values of 5-9. Kinetic measurements suggested that CBM6 had a crucial function in the ability of the enzyme to bind and hydrolyze xylan substrates, while LS had a relatively mild influence. Collectively, a noticeable thermostability and a high specific activity of XynNTU and its truncated form XynNTU-CDLS highlights their potentials for diverse industrial applications.

Purification and characterization of a highly-stable fungal xylanase from Aspergillus tubingensis cultivated on palm wastes through combined solid-state and submerged fermentation

Fungal xylanase was produced from lignocellulosic palm wastes through combined solid-state fermentation (SSF) and submerged fermentation (SmF) by Aspergillus tubingensis TSIP9 in a helical-impeller equipped bioreactor. The combined SSF-SmF promoted the xylanase production by 15 and 70% higher than SSF and SmF, respectively. Sequential purification yielded 7.4-fold purified xylanase with 9.07% recovery. The maximum activities of crude and purified xylanase were observed at the same pH of 5.0 and the same temperature of 50 °C while purified xylanase is more active and highly stable at a wider pH range of 3-8 and temperature of 30-60 °C. The half-life of purified xylanase at various temperatures was also much improved by 2-8 folds compared to crude xylanase. Michaelis-Menten constants, V_max and K_m, for purified xylanase are 2,602.8 U/mg and 32.4 mg/mL, respectively. Purified xylanase activity was most enhanced with Ca²⁺ followed by Zn²⁺ and Fe²⁺ at 10 mM while significantly inhibited by Co²⁺, Cu²⁺, Pb²⁺, and Ag⁺. This study has shown the effectiveness of combined SSF-SmF for xylanase production and superior properties of purified xylanase for industrial processes.

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.

Expression, Characterization and Its Deinking Potential of a Thermostable Xylanase From Planomicrobium glaciei CHR43

Genome mining is more and more widely used in identifying new enzymes from database. In the present study, we reported a putative xylanase, Pg-Xyn (WP_053166147.1), which originated from a psychrotolerant strain Planomicrobium glaciei CHR 43, and was identified from Genbank by genome mining. Sequence analysis and homology modeling showed that Pg-Xyn belongs to glycosyl hydrolase family 10. On the basis of heterologous expression in E. coli and biochemical characterization, we found Pg-Xyn was most active at pH 9.0 and 80°C and exhibited good stability from pH 5.0 to 12.0 and below 90°C. Pg-Xyn was slightly activated in the presence of Ca²⁺ and Mg²⁺, while it was strongly inhibited by Mn²⁺. The analysis of hydrolysis products showed that Pg-Xyn was an endo-β-1,4-xylanase. In addition, Pg-Xyn performed good deinking ability in a paper deinking test. In consideration of its unique properties, Pg-Xyn might be a promising candidate for application in the paper and pulp industries.

Probing the Relation Between Community Evolution in Dynamic Residue Interaction Networks and Xylanase Thermostability

Residue-residue interactions are the basis of protein thermostability. The molecular conformations of Streptomyces lividans xylanase (xyna_strli) and Thermoascus aurantiacus xylanase (xyna_theau) at 300K, 325K and 350K were obtained by Molecular Dynamics (MD) simulations. Dynamic weighted residue interaction networks were constructed and the rigid-communities were detected using the ESPRA algorithm and the Evolving Graph+Fast-Newman algorithm. The residues in the rigid-communities are primarily located in loop2, short helixes α2^', α3^', α4^' and helixes α3 and α4. Thus, the rigid-community is close to the N-terminus of xylanase, which is usually stabilized to increase thermostability using site-directed mutagenesis. The evolution of the rigid-community with increasing temperature shows a stable synergistic interaction between loop2, α2^', α3^' and α4^' in xyna_theau. In particular, the short helixes α2^' and α3^' form a "thermo helix" to promote thermostability. In addition, tight global interactions between loop2, α2^', α3^', α3, α4^' and α4 of xyna_theau are identified, consisting mainly of hydrogen bonds, van der Waals forces and π-π stacking. These residue interactions are more resistant to high temperatures than those in xyna_strli. Robust residue interactions within these secondary structures are key factors influencing xyna_strli and xyna_theau thermostability. Analyzing the rigid-community can elucidate the cooperation of secondary structures, which cannot be discovered from sequence and 3D structure alone.

Daqu microbiota exhibits species-specific and periodic succession features in Chinese baijiu fermentation process

Daqu, a brick-shaped product spontaneously fermented under an open environment, has been regarded as the starter of fermentation, raw enzyme preparation and raw materials for baijiu production. However, its contribution in baijiu fermentation has not been fully elaborated yet. Here, the effects of daqu microbiota on baijiu fermentation were investigated under both field-scale and lab-scale conditions. In field-scale baijiu fermentation, the dominant daqu microbes (average relative abundance>10.0%), including unclassified_Leuconostocaceae, Thermoascus, and Thermomyces, tended to dominate the early stage (0-7 d). However, the rare daqu microbes (average relative abundance <0.1%, e.g., Kazachstania) tended to dominate the middle and late stages (11-40 d). In addition, some genera showed differences in species diversity between daqu and fermented grains. The average relative abundance of Lactobacillus was over 75% during baijiu fermentation, and most of them were affiliated with Lactobacillus acetotolerans, while Lactobacillus crustorum dominated the Lactobacillus OTUs in daqu. The similar patterns were also observed during lab-scale baijiu fermentation. The results of function prediction showed the enriched metabolic pathways were associated with glycolysis and long-chain fatty acid esters in baijiu fermentation. These results improved the understanding of daqu microbiota function during baijiu fermentation and provided a basic theory to support the regulation of baijiu production.

Purification, characterization and partial amino acid sequences of thermo-alkali-stable and mercury ion-tolerant xylanase from Thermomyces dupontii KKU-CLD-E2-3

We investigated the properties of the low molecular weight thermo-alkali-stable and mercury ion-tolerant xylanase production from Thermomyces dupontii KKU-CLD-E2-3. The xylanase was purified to homogeneity by ammonium sulfate, Sephadex G-100 and DEAE-cellulose column chromatography which resulted 27.92-fold purification specific activity of 56.19 U/mg protein and a recovery yield of 2.01%. The purified xylanase showed a molecular weight of 25 kDa by SDS-PAGE and the partial peptide sequence showed maximum sequence homology to the endo-1,4-β-xylanase. The optimum temperature and pH for its activity were 80 °C and pH 9.0, respectively. Furthermore, the purified xylanase can maintain more than 75% of the original activity in pH range of 7.0-10.0 after incubation at 4 °C for 24 h, and can still maintain more than 70% of original activity after incubating at 70 °C for 90 min. Our purified xylanase was activated by Cu2+ and Hg2+ up to 277% and 235% of initial activity, respectively but inhibited by Co2+, Ag+ and SDS at a concentration of 5 mM. The Km and Vmax values of beechwood xylan were 3.38 mg/mL and 625 µmol/min/mg, respectively. Furthermore, our xylanase had activity specifically to xylan-containing substrates and hydrolyzed beechwood xylan, and the end products mainly were xylotetraose and xylobiose. The results suggested that our purified xylanase has potential to use for pulp bleaching in the pulp and paper industry.

Revisiting the scope and applications of food enzymes from extremophiles

Microorganisms from extreme environments tend to undergo various adaptations due to environmental conditions such as extreme pH, temperature, salinity, heavy metals, and solvents. Thus, they produce enzymes with unique properties and high specificity, making them useful industrially, particularly in the food industries. Despite these enzymes' remarkable properties, only a few instances can be reported for actual exploitation in the food industry. This review's objectives are to highlight the properties of these enzymes and their prospects in the food industry. First, an introduction to extremophilic organisms is presented, followed by the categories and application of food enzymes from extremophiles. Then, the unique structural features of extremozymes are shown. This review also covers the prospective applications of extremozymes in the food industry in a broader sense, including degradation of toxins, deconstruction of polymers into monomers, and catalysis of multistep processes. Finally, the challenges in bioprocessing of extremozymes and applications in food are presented. PRACTICAL APPLICATIONS: Enzymes are important players in food processing and preservation. Extremozymes, by their nature, are ideal for a broad range of food processing applications, particularly those that require process conditions of extreme pH, temperature, and salinity. As the global food industry grows, so too will grow the need to research and develop food products that are diverse, safe, healthy, and nutritious. There is also the need to produce food in a sustainable way that generates less waste or maximizes waste valorization. We anticipate that extremozymes can meet some of the research and development needs of the food industry.

Isolation and Selection of Streptomyces Species from Semi-arid Agricultural Soils and Their Potential as Producers of Xylanases and Cellulases

The Mezquital Valley (MV), Mexico, is a semi-arid region whose main economic activity is agriculture, this zone is characterized by the use of wastewater for crop irrigation. This condition has increased the amount nutrients in soils, organic carbon content and native microorganisms. The Streptomyces species are a group of saprophytic bacteria that represent between 20 and 60% of the total microbial population in soils, capable of producing metabolites of commercial importance. In this work, Streptomyces species were isolated from agricultural soils of the MV and was evaluated the production of endoglucanases (CMCase) and xylanases (Xyl) in Solid-State Cultivation (SSC). From soil samples, 73 possible strains of Streptomyces species were isolated for their ability to produce CMCase and Xyl in SSC. The study also included its characterization by morphological characteristics. Of the isolated microorganisms, 38 strains were selected as strong enzyme producers according to the measurement of the halo generated in plate and by growth on barley straw as only carbon source. Two different sizes of barley straw particle were tested, finding that the greatest enzymatic activity was observed in particle size 12. Three strains of Streptomyces species were chosen which presented the best catalytic capacities, a maximum of 100.69 AU Xyl/gram dry matter (gdm), 82 AU Xyl/gdm and 26.02 AU CMCase/gdm for strains 30, 28 and 12, respectively. The strains were identified by ribosomal gen16s sequence and identified as S. flavogriseus, S. virginiae and S. griseoaurantiacus. It is the first report of endogluconase and xylanolytic activity by S. virginiae isolated from a semi-arid soil.

Variations in Fungal Community and Diversity in Doushen With Different Flavors

Doushen, a traditional Chinese fermented soybean product, may be spiced or spicy depending on whether pepper powder is added. While numerous studies have investigated the microbial communities of other fermented foods, little is known on the fungal diversity of Doushen. Therefore, in this study, we investigated the fungal community and diversity in both spiced and spicy Doushen. Our results revealed that fungal species richness significantly differed between the samples with different flavors. A total of nine phyla and 188 fungal genera were identified, and Ascomycota and Aspergillus were predominant in all samples. Based on linear discriminant analysis, a total of 57 OTUs were significantly different between the two samples. Results of non-metric multidimensional scaling and unweighted pair-group analysis suggested that the presence of pepper powder affects the microbial community in Doushen. Network analysis showed that microbial interactions between fungal communities in Doushen with different flavors were significantly different. The results on the enumeration and identification of fungi were consistent with the composition of the dominant genera in the samples with different flavors. This study provides a theoretical basis for future research on food ecology in Doushen.

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.

Thermostable xylanases from thermophilic fungi and bacteria: Current perspective

Thermostable xylanases from thermophilic fungi and bacteria have a wide commercial acceptability in feed, food, paper and pulp and bioconversion of lignocellulosics with an estimated annual market of USD 500 Million. The genome wide analysis of thermophilic fungi clearly shows the presence of elaborate genetic information coding for multiple xylanases primarily coding for GH10, GH11 in addition to GH7 and GH30 xylanases. The transcriptomics and proteome profiling has given insight into the differential expression of these xylanases in some of the thermophilic fungi. Bioprospecting has resulted in identification of novel thermophilic xylanases that have been endorsed by the industrial houses for heterologous over- expression and formulations. The future use of xylanases is expected to increase exponentially for their role in biorefineries. The discovery of new and improvement of existing xylanases using molecular tools such as directed evolution is expected to be the mainstay to meet increasing demand of thermostable xylanases.

Enhancement of quality retention of Grifola frondosa fruiting bodies by erythorbic acid treatment

In this paper, the effects of erythorbic acid (EA) treatment with different concentrations on the quality of Grifola frondosa fruiting bodies stored at 4 °C for 27 days were studied by determining the changes in moisture content, weight loss, browning, electrolyte leakage, malondialdehyde (MDA), and nutritional compounds. The activities of polyphenoloxidase (PPO), cellulase and other antioxidant enzymes including superoxide dismutase (SOD), catalase, and peroxidase (POD) were also measured. Results showed that 0.1% EA-treated G. frondosa fruiting body maintained lower weight loss (< 6.0%, w/w), electrolyte leakage (< 45.8%), MDA (< 4.17 µmol kg-1), and higher moisture content (> 90.7%, w/w). Lower activities of PPO (< 72.64 × 103 U kg-1) and cellulase (< 189.86 × 103 U kg-1) in 0.1% EA-treated samples were observed compared with the other treatments. As a stereoisomer of ascorbic acid (AA), EA also could enhance SOD and POD activities of G. frondosa fruiting bodies. Our findings were the first time to evaluate the effect of EA on maintaining quality in G. frondosa fruiting bodies, and proved that low concentrations of EA (especially 0.1% EA, w/v) treatments were beneficial to preserve G. frondosa fruiting body with even higher efficiency than AA treatment. This study paved a foundation for the enhancement of quality retention of G. frondosa fruiting bodies.