A novel endo-β-1,4-xylanase from Pediococcus acidilactici GC25; purification, characterization and application in clarification of fruit juices

Advances in the understanding of the production, modification and applications of xylanases in the food industry

Xylanases have broad applications in the food industry to decompose the complex carbohydrate xylan. This is applicable to enhance juice clarity, improve dough softness, or reduce beer turbidity. It can also be used to produce prebiotics and increase the nutritional value in foodstuff. However, the low yield and poor stability of most natural xylanases hinders their further applications. Therefore, it is imperative to explore higher-quality xylanases to address the potential challenges that appear in the food industry and to comprehensively improve the production, modification, and utilization of xylanases. Xylanases, due to their various sources, exhibit diverse characteristics that affect production and activity. Most fungi are suitable for solid-state fermentation to produce xylanases, but in liquid fermentation, microbial metabolism is more vigorous, resulting in higher yield. Fungi produce higher xylanase activity, but bacterial xylanases perform better than fungal ones under certain extreme conditions (high temperature, extreme pH). Gene and protein engineering technology helps to improve the production efficiency of xylanases and enhances their thermal stability and catalytic properties.

Optimization of α-L-arabinofuranosidase CcABF on clarification and beneficial active substances in fermented ginkgo kernel juice by artificial neural network and genetic algorithm

This study aimed at using α-L-arabinofuranosidase CcABF to improve the clarity and active substances in fermented ginkgo kernel juice by artificial neural network (ANN) modeling and genetic algorithm (GA) optimization. A credible three-layer feedforward ANN model was established to predict the optimal parameters for CcABF clarification. The experiments proved the highest transmittance of 89.40% for fermented ginkgo kernel juice with this understanding, which exhibited a 25.56% increase over the unclarified group. With the clarification of CcABF, the antioxidant capacity in juice was enhanced with the increase of total phenolic and flavone contents, and the maximum DPPH and hydroxyl radical scavenging rates were increased by 89.71% and 26.65%, respectively. The contents of toxic ginkgolic acids declined markedly, while the active ingredients of ginkgetin and ginkgolide B showed a modest increase. Moreover, changes in free amino acids and volatile compounds improved the nutritive value and flavor of clarified fermented ginkgo kernel juice.

Cryptococcus laurentii: a wild yeast for xylanase production from agricultural by-products

The development of technologies that allow the production of enzymes at a competitive cost is of great importance for several biotechnological applications, and the use of agro-industrial by-products is an excellent alternative to minimize costs and reduce environmental impacts. This study aimed to produce endo-xylanases using agro-industrial substrates rich in hemicellulose as sources of xylan in culture media. For this purpose, the yeast Cryptococcus laurentti and five lignocellulosic materials (defatted rice bran, rice husk, corn cob, oat husks, and soybean tegument), with and without pretreatment, were used as a source of xylan for enzyme production. To insert the by-products in the culture medium, they were dried and treated (if applicable) with 4% (w.v-1) NaOH and then added in a concentration of 2% (w.v-1). The cultures were agitated for 96 h, and the aliquots were removed to determine the enzymatic activities. Among the by-products studied, the maximum activity (8.7 U. mL-1 at pH 7.3) was obtained where rice bran was used. In contrast, corn cob was the by-product that resulted in lower enzyme production (1.6 U.mL-1). Thus, the defatted rice bran deserves special attention in front of the other by-products used since it provides the necessary substrate for producing endo-xylanases by yeast.

Screening of Lactic Acid Bacteria Strains for Potential Sourdough and Bread Applications: Enzyme Expression and Exopolysaccharide Production

Twenty-eight strains of lactic acid bacteria (LAB) were characterized for the ability to express enzymes of interest (including protease, xylanase, α-amylase, laccase, and glucose oxidase) as well as the ability to produce exopolysaccharide (EPS). The screening of enzyme capability for all LAB strains proceeded in a progressive 3-stage manner that helps to profile the efficiency of LAB strains in expressing chosen enzymes (Stage 1), highlights the strains with affinity for flour as the substrate (Stage 2), and discerns strains that can adapt well in a simulated starter environment (Stage 3). The theoretical ability of LAB to express these enzymes was also assessed using Basic Local Alignment Search Tool (BLAST) analysis to identify the underlying genes in the whole genome sequence. By consolidating both experimental data and information obtained from BLAST, three LAB strains were deemed optimal in expressing enzymes, namely, Lb. delbrueckii subsp. bulgaricus (RBL 52), Lb. rhamnosus (RBL 102), and Lb. plantarum (ATCC 10241). Meanwhile, EPS-producing capabilities were observed for 10 out of 28 LAB strains, among which, Lactococcus lactis subsp. diacetylactis (RBL 37) had the highest total EPS yield (274.15 mg polysaccharide/L culture) and produced 46.2% polysaccharide with a molecular mass of more than 100 kDa.

Green alternatives to petroleum-based plastics: production of bioplastic from Pseudomonas neustonica strain NGB15 using waste carbon source

Polyhydroxyalkanoates have attracted great interest as a suitable alternative to petrochemical based plastics due to their outstanding properties such as biodegradability and biocompatibility. However, the biggest problem in the production of microbial polyhydroxyalkanoates is low cost-effectiveness. In this study, polyhydroxyalkanoate production was carried out using waste substrates with local isolates. Culture conditions were optimized to increase the polyhydroxyalkanoate production potential. The produced polyhydroxyalkanoate was characterized by FTIR analyses, and its metabolic pathway was determined by real-time PCR. According to the results, the best polyhydroxyalkanoate producer bacteria was characterized as Pseudomonas neustonica NGB15. The optimal culture conditions were detected as 30 g/L banana peel powder, 25 °C temperature, pH 8, and 4-day incubation time. Under the optimized conditions, 3.34 g/L PHA production was achieved. As a result of FTIR analyses, major peaks were obtained at 1723, 1277, 1261, 1097, 1054, and 993 cm-1. These peaks represent that the type of produced polyhydroxyalkanoate was poly-β-hydroxybutyrate. According to gene expression profile of NGB15, it was determined that Pseudomonas neustonica NGB15 produces PHA using the de novo fatty acid synthesis metabolic pathway. In conclusion, poly-β-hydroxybutyrate production by Pseudomonas neustonica NGB15 using a low-cost fermentation medium has been shown to be biotechnologically promising.

Enhancing the acid stability of the recombinant GH11 xylanase xynA through N-terminal substitution to facilitate its application in apple juice clarification

The utilization of xylanase in juice clarification is contingent upon its stability within acidic environments. We generated a mutant xynA-1 by substituting the N-terminal segment of the recombinant xylanase xynA to investigate the correlation between the N-terminal region of xylanase and its acid stability. The enzymatic activity of xynA-1 was found to be superior under acidic conditions (pH 5.0). It exhibited enhanced acid stability, surpassing the residual enzyme activity values of xynA at pH 4.0 (53.07 %), pH 4.5 (69.8 %), and pH 5.0 (82.4 %), with values of 60.16 %, 77.74 %, and 87.3 %, respectively. Additionally, the catalytic efficiency of xynA was concurrently improved. Through molecular dynamics simulation, we observed that N-terminal shortening induced a reduction in motility across most regions of the protein structure while enhancing its stability, particularly Lys131-Phe146 and Leu176-Gly206. Furthermore, the application of treated xynA-1 in the process of apple juice clarification led to a significant increase in clarity within a short duration of 20 min at 35 °C while ensuring the quality of the apple juice. This study not only enhances the understanding of the N-terminal region of xylanase but also establishes a theoretical basis for augmenting xylanase resources employed in fruit juice clarification.

A thermostable xylanase hydrolyzes several polysaccharides from Bacillus altitudinis JYY-02 showing promise for industrial applications

Polysaccharides have attracted immense attention as the largest source of bioactive compounds. Its bioavailability and bioactivity can be improved by utilizing degradation enzymes to reduce their molecular weight and viscosity. In this study, a 654 bp gene encoding xylanase was screened from the genome of Bacillus altitudinis JYY-02 and overexpressed in Escherichia coli Rosetta (DE3). The recombinant xylanase with a molecular weight of 27.98 kDa was purified (11.7-fold) using Ni-NTA affinity chromatography, with a 43.6% final yield. Through molecular docking, Glu, Arg, Tyr, and Trp were found to be the main amino acids involved in the interaction between xylanase and xylobiose. The effects of pH, temperature, metal ions, and substrates on xylanase activity were determined, and the results showed that the highest catalytic activity was displayed at pH 6.5, 50 °C temperature, with Cu2+ as an activator and xylan as the substrate. The Km (substrate concentration that yields a half-maximal velocity) and Vmax (maximum velocity) of recombinant xylanase were 6.876 mg/mL and 10984.183 μmol/mg∙pr/min, respectively. The recombinant xylanase was thermostable, with 85% and 39% of the enzymatic activity retained after 1 h at 60 °C and 1 h at 90 °C, respectively. The recombinant xylanase demonstrated a significant clarifying effect on fruit juices.

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.

Valorization of Brewer’s Spent Grain Using Biological Treatments and its Application in Feeds for European Seabass (Dicentrarchus labrax)

Brewer’s spent grain (BSG) is the main brewery industry by-product, with potential applications in the feed and food industries due to its carbohydrate composition. In addition, the lignocellulosic nature of BSG makes it an adequate substrate for carbohydrases production. In this work, solid-state fermentation (SSF) of BSG was performed with Aspergillus ibericus, a non-mycotoxin producer fungus with a high capacity to hydrolyze the lignocellulosic matrix of the agro-industrial by-products. SSF was performed at different scales to produce a crude extract rich in cellulase and xylanase. The potential of the crude extract was tested in two different applications: -(1) - the enzymatic hydrolysis of the fermented BSG and (2) - as a supplement in aquafeeds. SSF of BSG increased the protein content from 25% to 29% (w/w), while the fiber content was reduced to 43%, and cellulose and hemicellulose contents were markedly reduced to around 15%. The scale-up of SSF from 10 g of dry BSG in flasks to 50 g or 400 g in tray-type bioreactors increased 55% and 25% production of cellulase and xylanase, up to 323 and 1073 U g⁻¹ BSG, respectively. The optimum temperature and pH of maximal activities were found to be 55°C and pH 4.4 for xylanase and 50°C and pH 3.9 for cellulase, cellulase being more thermostable than xylanase when exposed at temperatures from 45°C to 60°C. A Box–Behnken factorial design was applied to optimize the hydrolysis of the fermented BSG by crude extract. The crude extract load was a significant factor in sugars release, highlighting the role of hydrolytic enzymes, while the load of fermented BSG, and addition of a commercial β-glucosidase were responsible for the highest phenolic compounds and antioxidant activity release. The lyophilized crude extract (12,400 and 1050 U g⁻¹ lyophilized extract of xylanase and cellulase, respectively) was also tested as an enzyme supplement in aquafeed for European seabass (Dicentrarchus labrax) juveniles. The dietary supplementation with the crude extract significantly improved feed and protein utilization. The processing of BSG using biological treatments, such as SSF with A. ibericus, led to the production of a nutritionally enriched BSG and a crude extract with highly efficient carbohydrases capable of hydrolyzing lignocellulosic substrates, such as BSG, and with the potential to be used as feed enzymes with remarkable results in improving feed utilization of an important aquaculture fish species.

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.

Biochemical characterization of xylanase GH11 isolated from Aspergillus niger BCC14405 (XylB) and its application in xylooligosaccharide production

OBJECTIVE

To develop an endo-β-1,4-xylanase with high specificity for production of prebiotic xylooligosaccharides that optimally works at moderate temperature desirable to reduce the energy cost in the production process.

RESULTS

The xylB gene, encoding for a glycosyl hydrolase family 11 xylanase from a thermoresistant fungus, Aspergillus niger BCC14405 was expressed in a methylotrophic yeast P. pastoris KM71 in a secreted form. The recombinant XylB showed a high specific activity of 3852 and 169 U mg^-1 protein on beechwood xylan and arabinoxylan, respectively with no detectable side activities against different forms of cellulose (Avicel Ò PH101 microcrystalline cellulose, phosphoric acid swollen cellulose and carboxymethylcellulose). The enzyme worked optimally at 45 °C, pH 6.0. It showed a specific cleavage pattern by releasing xylobiose (X2) as the major product from xylooligosaccharides (X3 to X6) substrates. The highest XOS yield of 708 mg g^-1 substrate comprising X2, X3 and X6 was obtained from beechwood xylan hydrolysis.

CONCLUSION

The enzyme is potent for XOS production and for saccharification of lignocellulosic biomass.

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.

Extremophilic Prokaryotic Endoxylanases: Diversity, Applicability, and Molecular Insights

Extremophilic endoxylanases grabbed attention in recent years due to their applicability under harsh conditions of several industrial processes. Thermophilic, alkaliphilic, and acidophilic endoxylanases found their employability in bio-bleaching of paper pulp, bioconversion of lignocellulosic biomass into xylooligosaccharides, bioethanol production, and improving the nutritious value of bread and other bakery products. Xylanases obtained from extremophilic bacteria and archaea are considered better than fungal sources for several reasons. For example, enzymatic activity under broad pH and temperature range, low molecular weight, cellulase-free activity, and longer stability under extreme conditions of prokaryotic derived xylanases make them a good choice. In addition, a short life span, easy cultivation/harvesting methods, higher yield, and rapid DNA manipulations of bacterial and archaeal cells further reduces the overall cost of the product. This review focuses on the diversity of prokaryotic endoxylanases, their characteristics, and their functional attributes. Besides, the molecular mechanisms of their extreme behavior have also been presented here.

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.

Preparation of chitosan from waste shrimp shells fermented with Paenibacillus jamilae BAT1

In this study, chitin extraction from shrimp shell powder (SSP) using locally isolated Paenibacillus jamilae BAT1 (GenBank: MN176658), the preparation of chitosan from the extracted chitin, and the characterization and biological activity (antimicrobial and antioxidant) of the prepared chitosan (PC) were investigated. It was determined that P. jamilae BAT1 did not have chitinase activity but showed high protease activity and protein removal potential. Optimum pH, shell concentration and incubation time for deproteinization were determined as 7.0, 60 g/L and 4 days, respectively. Addition of KH₂PO₄ or MgSO₄ did not affect chitin extraction and deproteinization yield. The maximum yields of deproteinization, demineralization and chitin extraction yields were 87.67, 41.95 and 24.5%, respectively. The viscosity-average molecular weight of PC was determined as 1.41 × 10⁵ g/mol. The deacetylation degree of PC (86%) was found to be higher that of commercial chitosan (CC) (78%). DPPH scavenging activity of PC (IC₅₀ 0.59 mg/mL) was higher than that of CC (IC₅₀ 3.72 mg/mL). PC was found to have higher antimicrobial activity against the bacteria E. coli and S. aureus and the yeast C. albicans when compared to CC. This is the first study on the use of the bacterium P. jamilae in biological chitin extraction.

Alkali-stable GH11 endo-β-1,4 xylanase (XynB) from Bacillus subtilis strain CAM 21: application in hydrolysis of agro-industrial wastes, fruit/vegetable peels and weeds

GH11 endo-xylanases, due to their inherent structural and biochemical properties, are the key to efficient bioconversion of lignocellulosic biomass into value-added products. A GH11 endo-xylanase (XynB) from Bacillus subtilis strain CAM 21 was cloned, over-expressed and purified (Mw∼24 kDa) using Ni-NTA affinity chromatography. XynB showed optimum activity at pH 7.0 and 50°C and was stable (>88%) in a broad range of pH (4-11). The apparent Km_, K_cat and K_cat/Km of XynB were 2.9 mg/ml, 1961.2/sec, and 675.62 ml/mg/sec, respectively using birchwood xylan as substrate. XynB was a classical endo-xylanase as it hydrolyzed birchwood xylan to xylo-oligosaccharides and not xylose. Kinetic stability of XynB at 45-53°C was between 43-182 min. Secondary structure analysis of XynB using far-UV CD spectroscopy revealed presence of 51.85% β strands and 2.64% α helix and was consistent with the homology modeling studies. XynB hydrolyzed the xylan extracted from agro-industrial wastes and fruit/vegetable peels by releasing up to 670 mg/g of reducing sugars. The xylan extracted from weeds (Ageratum conyzoides, Achyranthes aspera and Tridax procumbens) had characteristic signatures of hemicelluloses and after XynB hydrolysis showed cracks, peeling and release of up to 135.2 mg/g reducing sugars.

Highly alkali-stable and cellulase-free xylanases from Fusarium sp. 21 and their application in clarification of orange juice

Xylanase is a versatile tool in the food, fiber biobleaching and biofuel industries. Here, to discover new enzyme with special properties, we cloned three xylanases (Xyn11A, Xyn11B, and Xyn11C) by mining the genome of the xylanase producing fungus strain Fusarium sp. 21, biochemically characterized these enzyme and explored their potential application in juice processing. Both Xyn11A and Xyn11B had an optimal pH of 6.0 and optimal temperature of 45 °C, and retained >90% of the residual activity at pH range of 5-10.5 for 24 h. Xyn11C displayed the maximum activity at pH 5.0 and 45 °C and outstanding pH stability with a minimal loss of activity in the pH range of 2.0-10.5. These three xylanases displayed a strong specificity towards beechwood and corncob xylan, with no activity for other substrates. Xyn11A showed much a higher activity against corncob xylan, while Xyn11B and Xyn11C presented higher activities against beechwood xylan. Xyn11A catalyzed the hydrolysis of beechwood xylan with a K_m of 4.25 ± 0.29 mg·mL^-1 and k_cat/K_m of 30.34 ± 0.65 mL·s^-1·mg^-1, while the hydrolysis of corncob xylan had Km and k_cat/K_m values of 14.73 ± 1.43 mg·mL^-1and 26.48 ± 0.11 mL·s^-1·mg^-1, respectively. Xyn11B and Xyn11C hydrolyzed beechwood xylan with Km of 9.8 ± 0.69 mg·mL^-1, and 4.89 ± 0.38 mg·mL^-1and k_cat/K_m values of 45.07 ± 1.66 mL^-1·mg^-1, and 26.95 ± 0.67 mL·s^-1·mg^-1, respectively. Beechwood xylan hydrolysates catalyzed by these three xylanases contained xylobiose, xylotriose and xylooligosaccharides (XOS). The clarification of orange juice was improved when treated with these three xylanases. Conclusively, the desirable pH stability and substrate specificity make Xyn11A, Xyn11B and Xyn11C have high potential for application in fiber biobleaching, wine and fruit juice clarification, as well as probiotic XOS production.

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.

Polyphasic Characterization of Yeasts and Lactic Acid Bacteria Metabolic Contribution in Semi-Solid Fermentation of Chinese Baijiu (Traditional Fermented Alcoholic Drink): Towards the Design of a Tailored Starter Culture

Chinese Baijiu is principally produced through a spontaneous fermentation process, which involves complex microorganism communities. Among them, yeasts and lactic acid bacteria (LAB) are important communities. The study examined the isolated strains from fermented grains of Baijiu regarding their activity of α-amylase and glucoamylase, ethanol tolerance, glucose utilization, as well as metabolite production in the process of laboratory-scale sorghum-based fermentation. Selected strains (Saccharomycopsis fibuligera 12, Saccharomyces cerevisiae 3, and Pediococcus acidilactici 4) were blended in different combinations. The influence of selected strains on the metabolic variation in different semi-solid fermentations was investigated by gas chromatography–mass spectrometry (GC–MS) accompanied by multivariate statistical analysis. According to the principal component analysis (PCA), the metabolites produced varied in different mixtures of pure cultures. S. fibuligera produced various enzymes, particularly α-amylase and glucoamylase, and exhibited a better performance compared with other species regarding the ability to convert starch to soluble sugars and positively affect the production process of volatile compounds. S. cerevisiae had a high fermentation capacity, thereby contributing to substrates utilization. Lactic acid bacteria had a good ability to produce lactic acid. This study attaches importance to the special functions of S. fibuligera, S. cerevisiae, and P. acidilactici in Chinese Baijiu making, and investigates their metabolic characteristics in the process of lab-scale semi-solid fermentation.