Ultrahigh-Throughput Screening of High-ß-Xylosidase-Producing Penicillium piceum and Investigation of the Novel ß-Xylosidase Characteristics.

A droplet-based microfluidic ultrahigh-throughput screening technology has been developed for the selection of high-ß-xylosidase-producing Penicillium piceum W6 from the atmospheric and room-temperature plasma-mutated library of P. piceum. ß-xylosidase hyperproducers filamentous fungi, P. piceum W6, exhibited an increase in ß-xylosidase activity by 7.1-fold. A novel ß-D-xylosidase was purified from the extracellular proteins of P. piceum W6 and designated as PpBXL. The optimal pH and temperature of PpBXL were 4.0 and 70 °C, respectively. PpBXL had high stability an acidic pH range of 3.0-5.0 and exhibited good thermostability with a thermal denaturation half-life of 10 days at 70 °C. Moreover, PpBXL showed the bifunctional activities of α-L-arabinofuranosidase and ß-xylosidase. Supplementation with low-dose PpBXL (100 µg/g substrate) improved the yields of glucose and xylose generated from delignified biomass by 36-45%. The synergism between PpBXL and lignocellulolytic enzymes enhanced delignified biomass saccharification, increased the Xyl/Ara ratio, and decreased the strength of hydrogen bonds.

Purification of xylanases from Aureobasidium pullulans CCT 1261 and its application in the production of xylooligosaccharides.

Xylanolytic enzymes are involved in xylan hydrolysis, the main ones being endo-ß-1,4-xylanases (xylanases). This can be applied in the bioconversion of lignocellulosic materials into value-added products such as xylooligosaccharides (XOS). This study aimed to establish a protocol for the purification of xylanases, as well as to characterize and apply the purified enzyme extract in the production of XOS. The enzyme purification techniques studied were ammonium sulfate ((NH4)2SO4) and ethanol precipitation. Purification of xylanase by fractional precipitation (20-60%) with (NH4)2SO4 was more efficient than with ethanol because the salt precipitation reached a purification factor of 10.27-fold and an enzymatic recovery of 48.6% The purified xylanase exhibited optimum temperature and pH of 50 °C and 4.5, respectively. The Michaelis-Menten constant using beechwood xylan for the enzyme was 74.9 mg/mL. The addition of salts such as CaCl2, ZnCl2, and FeCl3 in the reaction medium increased the xylanase activity. Xylanase showed greater thermal stability (half-life = 169 h) at 45 °C and pH 4.5. Under these conditions and in the presence of Ca2+ (10 mmol/L) the enzyme was even more stable (half-life = 231 h). Total XOS contents (6.7 mg/mL) and the conversion of xylan to XOS (22.3%) between 2 and 24 h were statistically equal. The hydrolysates showed the majority composition of xylobiose, xylotriose, and xylose. The addition of Ca2+ ions did not contribute to an increase in the total XOS content or to a greater conversion of xylan into XOS, but the hydrolysate was richer in xylobiose and had a lower xylose content.

Biochemical properties of cellulolytic and xylanolytic enzymes from Sporotrichum thermophile and their utility in bioethanol production using rice straw.

Production of cellulolytic and xylanolytic enzymes by Sporotrichum thermophile was enhanced using response surface methodology in solid-state fermentation (SSF) using wheat straw and cotton oil cake. Cellulolytic and xylanolytic enzymes were partially purified by ammonium sulfate precipitation followed by ion exchange and gel filtration chromatographic techniques. Xylanase of S. thermophile is neutral xylanase displaying optimal activity at 60 °C with Km and Vmax values of 0.2 mg/mL and 238.05 µmole/min, respectively. All cellulases produced by the thermophilic mold showed optimal activity at pH 5.0 and 60 °C with Km values of 0.312 mg/mL, 0.113 mg/mL, and 0.285 mM for carboxymethyl cellulase (CMCase), filter paper cellulase (FPase), and ß-glucosidase, respectively and while Vmax values were 181.81, 138.88, and 66.67 µmole/min, respectively. The presence of various metal ions (Ca2+ and Co2+), chemical reagent (glutaraldehyde), and surfactants (Tween 80 and Triton X-100) significantly improved the activities of all enzymes. All the enzymes showed high storage stability under low temperature (-20 and 4 °C) conditions. Cellulolytic and xylanolytic enzymes resulted in enhanced liberation of reducing sugars (356.34 mg/g) by hydrolyzing both cellulosic and hemicellulosic fractions of ammonia-pretreated rice straw as compared to other pretreatment methods used in the study. Fermentation of enzymatic hydrolysate resulted in the formation of 28.88 and 27.18 g/L of bioethanol in separate hydrolysis and fermentation (SHF) process by Saccharomyces cerevisiae and Pichia stipitis, respectively. Therefore, cellulolytic and xylanolytic enzymes of S. thermophile exhibited ideal properties of biocatalysts useful in the saccharification of cellulosic and hemicellulosic fractions of rice straw for the production of bioethanol.

Xylanolytic Enzymes in Pulp and Paper Industry: New Technologies and Perspectives.

The pulp and paper industry discharges massive amount of wastewater containing hazardous organochlorine compounds released during different processing stages. Therefore, some cost-effective and nonpolluting practices such as enzymatic treatments are required for the potential mitigation of effluents released in the environment. Various xylanolytic enzymes such as xylanases, laccases, cellulases and hemicellulases are used to hydrolyse raw materials in the paper manufacturing industry. These enzymes are used either individually or in combination, which has the efficient potential to be considered for bio-deinking and bio-bleaching components. They are highly dynamic, renewable, and high in specificity for enhancing paper quality. The xylanase act on the xylan and cellulases act on the cellulose fibers, and thus increase the bleaching efficacy of paper. Similarly, hemicellulase enzyme like endo-xylanases, arabinofuranosidase and ß-D-xylosidases have been described as functional properties towards the biodegradation of biomass. In contrast, laccase enzymes act as multi-copper oxidoreductases, bleaching the paper by the oxidation and reduction process. Laccases possess low redox potential compared to other enzymes, which need some redox mediators to catalyze. The enzymatic process can be affected by various factors such as pH, temperature, metal ions, incubation periods, etc. These factors can either increase or decrease the efficiency of the enzymes. This review draws attention to the xylanolytic enzyme-based advanced technologies for pulp bleaching in the paper industry.

Fungal xylanolytic enzymes: Diversity and applications.

As important polysaccharide degraders in nature, fungi can diversify their extensive set of carbohydrate-active enzymes to survive in ecological habitats of various composition. Among these enzymes, xylanolytic ones can efficiently and sustainably degrade xylans into (fermentable) monosaccharides to produce valuable chemicals or fuels from, for example relevant for upgrading agro-food industrial side streams. Moreover, xylanolytic enzymes are being used in various industrial applications beyond biomass saccharification, e.g. food, animal feed, biofuel, pulp and paper. As a reference for researchers working in related areas, this review summarized the current knowledge on substrate specificity of xylanolytic enzymes from different families of the Carbohydrate-Active enZyme database. Additionally, the diversity of enzyme sets in fungi were discussed by comparing the number of genes encoding xylanolytic enzymes in selected fungal genomes. Finally, to support bio-economy, the current applications of fungal xylanolytic enzymes in industry were reviewed.

Production of xylose through enzymatic hydrolysis of glucuronoarabinoxylan from brewers' spent grain.

Xylose is an abundant bioresource for obtaining diverse chemicals and added-value products. The production of xylose from green alternatives like enzymatic hydrolysis is an important step in a biorefinery context. This research evaluated the synergism among four classes of hydrolytic purified enzymes-endo-1,4-ß-xylanase, α-L-arabinofuranosidase, ß-xylosidase, and α-D-glucuronidase-over hydrolysis of glucuronoarabinoxylan (GAX) obtained from brewers' spent grain (BSG) after alkaline extraction and ethanol precipitation. First, monosaccharides, uronic acids and glycosidic-linkages of alkaline extracted GAX fraction from BSG were characterized, after that different strategies based on the addition of one or two families of enzymes-endo-1,4-ß-xylanase (GH10 and GH11) and α-L-arabinofuranosidase (GH43 and GH51)-cooperating with one ß-xylosidase (GH43) and one α-D-glucuronidase (GH67) into enzymatic hydrolysis were assessed to obtain the best yield of xylose. The xylose release was monitored over time in the first 90 min and after a prolonged reaction up to 48 h of reaction. The highest yield of xylose was 63.6% (48 h, 40 â„ƒ, pH 5.5), using a mixture of all enzymes devoid of α-L-arabinofuranosidase (GH43) family. These results highlight the importance of GH51 arabinofuranosidase debranching enzyme to allow a higher cleavage of the xylan backbone of GAX from BSG and their synergy with 2 endo-1,4-ß-xylanase (GH10 and GH11), one ß-xylosidase (GH43) and the inclusion of one α-D-glucuronidase (GH67) in the reaction system. Therefore, this study provides an environmentally friendly process to produce xylose from BSG through utilization of enzymes as catalysts.

Xylanolytic enzyme consortia from Bacillus sp. NIORKP76 for improved biobleaching of kraft pulp.

A cellulase-free xylanolytic enzyme consortia consisting of a xylanase, arabinofuranosidase, and acetyl xylan esterase produced by Bacillus sp. NIORKP76 isolate under solid-state fermentation was assessed for its bio-bleaching ability on kraft pulp. In the biobleaching analysis, the xylanase dose of 5 Ug-1 dry pulp denoted the optimum bleaching of pulp at 40 °C and pH 8.0 after 2 h of treatment. The reduction in kappa number of pre-treated hardwood pulp using xylanolytic enzyme consortium (XEC) was found to be ~ 55%, while solo xylanase could reduce the kappa number to 44-46%. In the case of chemical bagasse pulp, a reduction of ~ 27.5% and 19-20% was seen in kappa number using XEC and solo xylanase, respectively. Enzyme-treated pulp (HW and CB) showed a 50% reduction in hypochlorite consumption during the chlorine treatment. The current study results reveal the significant potential of xylanolytic enzyme consortium from Bacillus sp. NIORKP76 on the environmentally friendly bio-bleaching process.

Rational engineering of xylanase hyper-producing system in Trichoderma reesei for efficient biomass degradation.

BACKGROUND: Filamentous fungus Trichoderma reesei has been widely used as a workhorse for cellulase and xylanase productions. Xylanase has been reported as the crucial accessory enzyme in the degradation of lignocellulose for higher accessibility of cellulase. In addition, the efficient hydrolysis of xylan needs the co-work of multiple xylanolytic enzymes, which rise an increasing demand for the high yield of xylanase for efficient biomass degradation. RESULTS: In this study, a xylanase hyper-producing system in T. reesei was established by tailoring two transcription factors, XYR1 and ACE1, and homologous overexpression of the major endo-xylanase XYNII. The expressed xylanase cocktail contained 5256 U/mL xylanase activity and 9.25 U/mL ß-xylosidase (pNPXase) activity. Meanwhile, the transcription level of the xylanolytic genes in the strain with XYR1 overexpressed was upregulated, which was well correlated with the amount of XYR1-binding sites. In addition, the higher expression of associated xylanolytic enzymes would result in more efficient xylan hydrolysis. Besides, 2310-3085 U/mL of xylanase activities were achieved using soluble carbon source, which was more efficient and economical than the traditional strategy of xylan induction. Unexpectedly, deletion of ace1 in C30OExyr1 did not give any improvement, which might be the result of the disturbed function of the complex formed between ACE1 and XYR1. The enzymatic hydrolysis of alkali pretreated corn stover using the crude xylanase cocktails as accessory enzymes resulted in a 36.64% increase in saccharification efficiency with the ratio of xylanase activity vs FPase activity at 500, compared to that using cellulase alone. CONCLUSIONS: An efficient and economical xylanase hyper-producing platform was developed in T. reesei RUT-C30. The novel platform with outstanding ability for crude xylanase cocktail production would greatly fit in biomass degradation and give a new perspective of further engineering in T. reesei for industrial purposes.

Xylanolytic Extremozymes Retrieved From Environmental Metagenomes: Characteristics, Genetic Engineering, and Applications.

Xylanolytic enzymes have extensive applications in paper, food, and feed, pharmaceutical, and biofuel industries. These industries demand xylanases that are functional under extreme conditions, such as high temperature, acidic/alkaline pH, and others, which are prevailing in bioprocessing industries. Despite the availability of several xylan-hydrolyzing enzymes from cultured microbes, there is a huge gap between what is available and what industries require. DNA manipulations as well as protein-engineering techniques are also not quite satisfactory in generating xylan-hydrolyzing extremozymes. With a compound annual growth rate of 6.6% of xylan-hydrolyzing enzymes in the global market, there is a need for xylanolytic extremozymes. Therefore, metagenomic approaches have been employed to uncover hidden xylanolytic genes that were earlier inaccessible in culture-dependent approaches. Appreciable success has been achieved in retrieving several unusual xylanolytic enzymes with novel and desirable characteristics from different extreme environments using functional and sequence-based metagenomic approaches. Moreover, the Carbohydrate Active Enzymes database includes approximately 400 GH-10 and GH-11 unclassified xylanases. This review discusses sources, characteristics, and applications of xylanolytic enzymes obtained through metagenomic approaches and their amelioration by genetic engineering techniques.

Production of xylanases by Bacillus sp. TC-DT13 in solid state fermentation using bran wheat.

Xylanases have gained increasing importance due to their diverse applications in the food, paper, and pharmaceutical industries, however, the production of these enzymes currently uses expensive substrates. It has already been estimated that more than 30% of the enzyme production cost originates from the substrate. The present study aimed to optimize the production of extracellular xylanases by the Bacillus sp. TC-DT 13 using solid-state fermentation with agro-industrial residues, with a view at reducing the production cost of these enzymes. All the agro-industrial residues were tested in submerged fermentation to select the best inductor to produce xylanase. Among these residues, wheat bran was selected as the best inducer of xylanase production with 1500 U/mL. Regarding solid-state fermentation, the use of wheat bran as the only fermentation substrate was used and a ratio of 1:4 moisture over a time of 144 hours induced higher amount of xylanase reaching 2943 U/g. The use of carbon and nitrogen sources did not result in the increase in production of xylanolitic enzymes. The use of agro-industrial residues in the solid-state fermentation, besides increasing the production of xylanase, reduces the cost of production and is an environmentally friendly alternative.

Xylooligosaccharides production from wheat middlings bioprocessed with Bacillus subtilis.

Prebiotic compounds are substrates selectively metabolized by beneficial gut microbiota causing a health-promoting effect. Despite some prebiotic carbohydrates have been largely studied, xylooligosaccharides (XOS) are important prebiotics derived from arabinoxylans, which are polysaccharides found in cereals. This study aimed to investigate the production of xylanolytic enzymes and XOS during bioprocessing of wheat middlings, a product derived from wheat flour production, using a probiotic Bacillus subtilis. The composition of XOS and the enzymatic and prebiotic activities of resulting B. subtilis cultures were evaluated. The activity of xylanolytic enzymes continuously enhanced during the 72 h bacterial growth, where ß-xylosidase presented the highest value (70.31 U/mL). XOS profile and concentration varied considerably between control and bioprocessed samples and among these at different times. Maximum prebiotic activity score was found for the 24 h and 72 h bioprocessed samples (1.73 and 1.61, respectively) using the commercial probiotic Lactobacillus acidophilus LA-5. Wheat middlings showed to be a promising substrate for production of prebiotics like XOS and B. subtilis FTC01 appears to be a good source of xylanolytic enzymes.

Improving the thermostability of Trichoderma reesei xylanase 2 by introducing disulfide bonds

Background: Xylanases are considered one of the most important enzymes in many industries. However, their low thermostability hampers their applications in feed pelleting, pulp bleaching, and so on. The main aim of this work was to improve the thermostability of Trichoderma ressei xylanase 2 (Xyn2) by introducing disulfide bonds between the N-terminal and α-helix and the ß-sheet core. Results: In this work, two disulfide bonds were separately introduced in the Xyn2 to connect the N-terminal and α-helix to the ß-sheet core of Xyn2. The two disulfide bonds were introduced by site-directed mutagenesis of the corresponding residues. The half-life of the mutants Xyn2C14­52 (disulfide bond between ß-sheets B2 and B3) and Xyn2C59­149 (disulfide bond between ß-sheets A5 and A6) at 60°C was improved by approximately 2.5- and 1.8-fold compared to that of the wild type Xyn2. In addition, the enzyme's resistance to alkali and acid was enhanced. Conclusion: Our results indicated that the connection of the N-terminal and α-helix to the ß-sheet core is due to the stable structure of the entire protein.

Towards enzymatic breakdown of complex plant xylan structures: State of the art.

Significant progress over the past few years has been achieved in the enzymology of microbial degradation and saccharification of plant xylan, after cellulose being the most abundant natural renewable polysaccharide. Several new types of xylan depolymerizing and debranching enzymes have been described in microorganisms. Despite the increasing variety of known glycoside hydrolases and carbohydrate esterases, some xylan structures still appear quite recalcitrant. This review focuses on the mode of action of different types of depolymerizing endoxylanases and their cooperation with ß-xylosidase and accessory enzymes in breakdown of complex highly branched xylan structures. Emphasis is placed on the enzymatic hydrolysis of alkali-extracted deesterified polysaccharide as well as acetylated xylan isolated from plant cell walls under non-alkaline conditions. It is also shown how the combination of selected endoxylanases and debranching enzymes can determine the nature of prebiotic xylooligosaccharides or lead to complete hydrolysis of the polysaccharide. The article also highlights the possibility for discovery of novel xylanolytic enzymes, construction of multifunctional chimeric enzymes and xylanosomes in parallel with increasing knowledge on the fine structure of the polysaccharide.

Xylanase and beta-xylosidase from Penicillium janczewskii: Purification, characterization and hydrolysis of substrates

Background: Xylanases and β-D-xylosidases are the most important enzymes responsible for the degradation of xylan, the second main constituent of plant cell walls. Results: In this study, the main extracellular xylanase (XYL I) and p-xylosidase (BXYL I) from the fungus Penicillium janczewskii were purified, characterized and applied for the hydrolysis of different substrates. Their molecular weights under denaturing and non-denaturing conditions were, respectively, 30.4 and 23.6 kDa for XYL I, and 100 and 200 kDa for BXYL I, indicating that the latter is homodimeric. XYL I is highly glycosylated (78%) with optimal activity in pH 6.0 at 65°C, while BXYL I presented lower sugar content (10.5%) and optimal activity in pH 5.0 at 75°C. The half-lives of XYL I at 55, 60 and 65°C were 125,16 and 6 min, respectively. At 60°C, BXYL I retained almost 100% of the activity after 6 h. NH4+,Na+, DTT and β-mercaptoethanol stimulated XYL I, while activation of BXYL I was not observed. Interestingly, XYL I was only partially inhibited by Hg2+, while BXYL I was completely inhibited. Xylobiose, xylotriose and larger xylooligosaccharides were the main products from xylan hydrolysis by XYL I. BXYL I hydrolyzed xylobiose and larger xylooligosaccharides with no activity against xylans. Conclusion: The enzymes act synergistically in the degradation of xylans, and present industrial characteristics especially in relation to optimal activity at high temperatures, prolonged stability of BXYL I at 60°C, and stability of XYL I in wide pH range.

Sensitization to xylanolytic enzymes: an underestimated health hazard among bakers.

BACKGROUND: The most important occupational allergens in baking include flour and enzymes, especially α-amylase. Although xylanolytic enzymes have previously been described as sensitizers, they may be overlooked during assessment of bakery workers with work-related symptoms. AIMS: To report a case of a baker who suffered from work-related respiratory, ocular and skin symptoms as a consequence of sensitization to xylanolytic enzymes. METHODS: Physical examination, chest X-ray, routine laboratory tests, skin prick tests (SPTs) with common and occupational allergens (wheat, pearl, rye, corn and oat flours, α-amylase, bakery adjuvants) and spirometric measurements, as well as assessments by a laryngologist, dermatologist and ophthalmologist were performed. Specific IgE (sIgE) to occupational agents were evaluated for flours, α-amylase, xylanase, cellulose and glucoamylase. Specific inhalation challenges (SICs) with flours and bakery adjuvants were carried out. RESULTS: Hypersensitivity to Aspergillus moulds, flours and α-amylase was confirmed in SPTs; however, SIC with those agents gave a negative result. Further investigation revealed the presence of sIgE to xylanolytic enzymes. During SIC with bakery adjuvants, allergic skin, ocular and respiratory symptoms occurred and were confirmed by objective assessment. CONCLUSIONS: In the assessment of work-related allergic symptoms in bakers, sensitization to xylanolytic enzymes should be considered. Completion of diagnostic procedures having excluded asthma and rhino-conjunctivitis related to flour hypersensitivity might result in a false-negative assessment.

Molecular cloning and comparative sequence analysis of fungal ß-Xylosidases.

Commercial scale degradation of hemicelluloses into easily accessible sugar residues is practically crucial in industrial as well as biochemical processes. Xylanolytic enzymes have a great number of possible applications in many biotechnological processes and therefore, these enzymes are continuously attracting the attention of scientists. Due to this fact, different ß-Xylosidases have been isolated, purified and characterized from several bacteria and fungi. Microorganisms in this respect have gained much momentum for production of these significant biocatalysts with remarkable features. It is difficult to propagate microorganisms for efficient and cost-competitive production of ß-Xylosidase from hemicelluloses due to expensive conditions of fermentation. The screening of new organisms with an enhanced production of ß-Xylosidases has been made possible with the help of recombinant DNA technology. ß-Xylosidase genes haven been cloned and expressed on large scale in both homologous and heterologous hosts with the advent of genetic engineering. Therefore, we have reviewed the literature regarding cloning of ß-Xylosidase genes into various hosts for their heterologous production along with sequence similarities among different ß-Xylosidases. The study provides insight into the current status of cloning, expression and sequence analysis of ß-Xylosidases for industrial applications.

Solid-state fermentation of brewer's spent grain for xylanolytic enzymes production by Penicillium janczewskii and analyses of the fermented substrate / Fermentação em estado sólido com bagaço de cevada para produção de enzimas xilanolíticas por Penicillium janczewskii e análise do substrato fermentado

In recent decades, increasing interest has been devoted to xylanolytic enzymes due to their potential use in many industrial processes. This study describes the production of xylanase, -xylosidase and -Larabinofuranosidase, belonging to the xylanolytic complex, by Penicillium janczewskii using brewer's spent grain as substrate for solid-state fermentation. The optimized conditions for high levels of xylanase, -xylosidase and -Larabinofuranosidase production were: 50% initial moisture, which was provided by Vogel's salt solution, seven days of cultivation at 20-30 °C. Fermentation enriched the bioproduct with some amino acids and did not add mycotoxins to it. The use of brewer's spent grain as substrate for fungal cultivation and enzyme production can both add value to this waste and reduce the production cost of xylanolytic enzymes.

Nas últimas décadas, há interesse crescente nas enzimas xilanolíticas devido à sua potencial utilização em muitos processos industriais. Este estudo descreve a produção de xilanase, -xilosidase e -Larabinofuranosidase, três enzimas do complexo xilanolítico, por Penicillium janczewski utilizando bagaço de cevada como substrato para fermentação em estado sólido. As condições selecionadas para a produção de elevados níveis de xilanase, - xilosidase e -L-arabinofuranosidase por esta linhagem fúngica foram 50% de umidade inicial, sendo esta fornecida por uma solução de sais de Vogel e cultivo por sete dias a 20-30 °C. O bioproduto fermentado foi enriquecido com alguns aminoácidos e se apresentou livre de micotoxinas. O uso do bagaço de cerveja como substrato para o cultivo de fungos e produção de enzimas não só pode agregar valor a esses resíduos, mas também reduzir o custo de produção de enzimas xilanolíticas.

Selection and molecular characterization of cellulolytic-xylanolytic fungi from surface soil-biomass mixtures from Black Belt sites.

Plant biomass is an abundant renewable natural resource that can be transformed into chemical feedstocks. Enzymes used in saccharification of lignocellulosic biomass are a major part of biofuel production costs. A cocktail of cellulolytic and xylanolytic enzymes are required for optimal saccharification of biomass. Accordingly, thirty-two fungal pure cultures were obtained from surface soil-biomass mixtures collected from Black Belt sites in Alabama by culturing on lignocellulosic biomass medium. The fungal strains were screened for the coproduction of cellulolytic and xylanolytic enzymes. Strains that displayed promising levels of cellulolytic and xylanolytic enzymes were characterized by molecular analysis of DNA sequences from the large subunit and internal transcribed spacer (ITS) of their ribosomal RNA gene. Nucleotide sequence analysis revealed that two most promising isolates FS22A and FS5A were most similar to Penicillium janthinellum and Trichoderma virens. Production dynamics of cellulolytic and xylanolytic enzymes from these two strains were explored in submerged fermentation. Volumetric productivity after 120 h incubation was 121.08 units/L/h and 348 units/L/h for the filter paper cellulase and xylanase of strain FS22A, and 90.83 units/L/h and 359 units/L/h, respectively for strain FS5A. Assays with 10 times dilution of enzymes revealed that the activities were much higher than that observed in the crude culture supernatant. Additionally, both FS22A and FS5A also produced amylase in lignocellulose medium. The enzyme profiles of these strains and their activities suggest potential applications in cost effective biomass conversion and biodegradation.

Production of xylanases by an Aspergillus niger strain in wastes grain / Produção de xilanases por uma linhagem de Aspergillus niger em resíduos de grãos

Many fungi are used in order to extract products from their metabolism through bioprocesses capable of minimizing adverse effects caused by agro- industrial wastes in the environment. The aim of this study was to evaluate the xylanase production by an Aspergillus niger strain, using agro-industrial wastes as substrate. Brewer's spent grain was the best inducer of xylanase activity. Higher levels of xylanase were obtained when the fungus was grown in liquid Vogel medium, pH 5.0, at 30ºC, during 5 days. The temperature for optimum activity was 50ºC and optimum pH 5.0. The enzyme was stable at 50ºC, with a half-life of 240 min. High pH stability was verified from pH 4.5 to 7.0. These characteristics exhibited by A. niger xylanase turn this enzyme attractive for some industrial applications, such as in feed and food industries. Additionally, the use of brewer's spent grain, an abundantly available and low-cost residue, as substrate for xylanase production can not only add value and decrease the amount of this waste, but also reduce xylanase production cost.

Muitos fungos são utilizados com a finalidade de extrair produtos de seu metabolismo, por meio de bioprocessos capazes de minimizar efeitos nocivos que resíduos agroindustriais causam ao meio ambiente. O objetivo deste estudo foi avaliar a produção de xilanases por uma linhagem de Aspergillus niger, empregando resíduos agroindustriais como substrato. O bagaço de malte foi o melhor resíduo indutor da atividade xilanásica. Maiores níveis de xilanases foram obtidos quando o fungo foi cultivado em meio líquido de Vogel, pH 5,0, a 30ºC, durante cinco dias. A temperatura ótima estabelecida para a atividade xilanásica foi a de 50ºC e o pH ótimo 5,0. A enzima foi estável a 50ºC, apresentando uma meia vida de 240 min. Elevada estabilidade enzimática foi verificada entre os pH 4,5 e 7,0. As características bioquímicas exibidas pela xilanase produzida por A. niger tornam esta enzima atraente para determinadas aplicações industriais, como as indústrias de ração animal e alimentícia. Adicionalmente, a utilização do bagaço de malte, um resíduo disponível em abundância e de baixo custo como substrato para a produção de xilanases poderá não somente adicionar valor a este resíduo, como também reduzir os custos de produção destas enzimas.

ß-xylosidases and α-L-arabinofuranosidases: accessory enzymes for arabinoxylan degradation.

Arabinoxylan (AX) is among the most abundant hemicelluloses on earth and one of the major components of feedstocks that are currently investigated as a source for advanced biofuels. As global research into these sustainable biofuels is increasing, scientific knowledge about the enzymatic breakdown of AX advanced significantly over the last decade. This review focuses on the exo-acting AX hydrolases, such as α-arabinofuranosidases and ß-xylosidases. It aims to provide a comprehensive overview of the diverse substrate specificities and corresponding structural features found in the different glycoside hydrolase families. A careful review of the available literature reveals a marked difference in activity between synthetically labeled and naturally occurring substrates, often leading to erroneous enzymatic annotations. Therefore, special attention is given to enzymes with experimental evidence on the hydrolysis of natural polymers.