A novel cellulase free alkaliphilic xylanase from alkali tolerant Penicillium citrinum: production, purification and characterization

Novel Cellulase Screening and Optimal Production from the Wood Decaying Xylariaceae: Daldinia Species

The highest cellulases production from Daldinia caldariorum 263 (D-263) was found among Daldinia eschscholzii and Daldinia childiae. Three cellulases, one xylanase and one β-glucosidase of the molecular weights 55, 43, 34, 30, and 105 kDa, respectively, were determined by zymographic sodium dodecyl sulfate polyacrylamide gel electrophoresis. From the N-terminal sequencing, the major cellulase CelA belonging to glycosyl hydrolase family 5 was determined. By following an orthogonal experiment design (L9), factors affecting the cultivation of D. caldariorum 263 are ranked as medium composition > temperature > pH ≥ FP (%). The optimum cultivation conditions for obtaining the best FPase (600 mU/ml) at 72 h are 150 rpm, 35 °C, pH 7, 0.2% soy peptone and 0.5% α-cellulose in minimal requirement medium. In comparison with Trichoderma reesei (ATCC26921) secreting 1,135 mU/ml of FPase after 6 days cultivation at pH 5, D. caldariorum 263 grew faster at 35 °C and produced the maximum FPase within 3 days at pH 7.

Directed Modification of a GHF11 Thermostable Xylanase AusM for Enhancing Inhibitory Resistance towards SyXIP-I and Application of AusMPKK in Bread Making

To reduce the inhibition sensitivity of a thermoresistant xylanase AusM to xylanase inhibitor protein (XIP)-type in wheat flour, the site-directed mutagenesis was conducted based on the computer-aided redesign. First, fourteen single-site variants and one three-amino acid replacement variant in the thumb region of an AusM-encoding gene (AusM) were constructed and expressed in E. coli BL21(DE3), respectively, as predicted theoretically. At a molar ratio of 100:1 between SyXIP-I/xylanase, the majority of mutants were nearly completely inactivated by the inhibitor SyXIP-I, whereas AusMN127A retained 62.7% of its initial activity and AusMPKK retained 100% of its initial activity. The optimal temperature of the best mutant AusMPKK was 60 °C, as opposed to 60-65 °C for AusM, while it exhibited improved thermostability, retaining approximately 60% of its residual activity after heating at 80 °C for 60 min. Furthermore, AusMPKK at a dosage of 1000 U/kg was more effective than AusM at 4000 U/kg in increasing specific bread loaf volume and reducing hardness during bread production and storage. Directed evolution of AusM significantly reduces inhibition sensitivity, and the mutant enzyme AusMPKK is conducive to improving bread quality and extending its shelf life.

Isolation and Characterization of Xylanase from a Novel Strain, Penicillium menonorum SP10

Xylanase has been applied in various sectors, such as biomass conversion, paper, pulp, textiles, and pharmaceutical industries. This study aimed to isolate and screen potential xylanase-producing fungi from the soil of Suphan Buri Province, Thailand. Fifteen fungi were isolated, and their xylanase activities were tested by the qualitative method. The result showed that isolate SP3, SP10 and SP15 gave high xylanase activity with potency index (PI) of 2.32, 2.01 and 1.82, respectively. These fungi were selected for the xylanase quantitative test, isolate SP10 performed the highest xylanase activity with 0.535 U/mL. Through molecular methods using the β-tubulin gene, isolate SP10 was identified as Penicillium menonorum. The xylanase characteristics from P. menonorum SP10 were determined, including the xylanase isoforms and the optimum pH and temperature. The xylanase isoforms on SDS-PAGE indicated that P. menonorum SP10 produced two xylanases (45 and 54 kDa). Moreover, its xylanase worked optimally at pH 6 and 55 °C while reaching 61% activity at 65 °C. These results proposed P. menonorum SP10 as a good candidate for industrial uses, especially in poultry feed and pulp industries, to improve yield and economic efficiency under slightly acidic and high-temperature conditions.

Alkaliphilic/Alkali-Tolerant Fungi: Molecular, Biochemical, and Biotechnological Aspects

Biotechnologist interest in extremophile microorganisms has increased in recent years. Alkaliphilic and alkali-tolerant fungi that resist alkaline pH are among these. Alkaline environments, both terrestrial and aquatic, can be created by nature or by human activities. Aspergillus nidulans and Saccharomyces cerevisiae are the two eukaryotic organisms whose pH-dependent gene regulation has received the most study. In both biological models, the PacC transcription factor activates the Pal/Rim pathway through two successive proteolytic mechanisms. PacC is a repressor of acid-expressed genes and an activator of alkaline-expressed genes when it is in an active state. It appears, however, that these are not the only mechanisms associated with pH adaptations in alkali-tolerant fungi. These fungi produce enzymes that are resistant to harsh conditions, i.e., alkaline pH, and can be used in technological processes, such as in the textile, paper, detergent, food, pharmaceutical, and leather tanning industries, as well as in bioremediation of pollutants. Consequently, it is essential to understand how these fungi maintain intracellular homeostasis and the signaling pathways that activate the physiological mechanisms of alkali resistance in fungi.

An environment-benign approach of bamboo pulp bleaching using extracellular xylanase of strain Bacillus stratosphericus EB-11 isolated from elephant dung

The use of microbial enzymes is highly encouraged in paper and pulp industries to reduce the excessive use of hazardous chemicals. During the study, xylanase of Bacillus stratosphericus EB-11 was characterized for pulp bleaching applications. The extracellular xylanase was produced under submerged fermentation using bamboo waste as a natural carbon source. There was fast cell division and enzyme production under optimized fermentation conditions in the bioreactor. The highest activity was 91,200U after 30 h of growth with Km and Vmax of 3.52 mg/mL and 391.5 μmol/min per mg respectively. The purified enzyme with molecular mass ~ 60 kDa had conferred positive activity on native PAGE. The strong inhibition by ethylenediaminetetraacetate and SDS showed the metallo-xylanase nature of the purified enzyme. The bacterial xylanase reduces the use of hydrogen peroxide by 0.4%. Similarly, biological oxygen demand and chemical oxygen demand were reduced by 42.6 and 35.2%. The xylanase-hydrogen peroxide combined treatment and conventional chlorine dioxide-alkaline (CDE₁D₁D₂) bleaching showed almost similar improvement in physicochemical properties of bamboo pulp. Xylanase-peroxide bleaching reduces the lignin content to 4.95% from 13.32% unbleached pulp. This content after CDE₁D₁D₂ treatment was 4.21%. The kappa number decreased from 15.2 to 9.46 with increasing the burst factor (15.51), crystallinity index (60.25%), viscosity (20.1 cp), and brightness (65.4%). The overall finding will encourage the development of new cleaner methods of bleaching in the paper and pulp industry.

Three-Step Purification and Characterization of Organic Solvent-Tolerant and Alkali-Thermo-Tolerant Xylanase from Bacillus paramycoides T4 [MN370035]

In the present study, an extracellular alkali-thermo-tolerant xylanase from Bacillus paramycoides was produced in the presence of an organic solvent. The enzyme was purified by ammonium sulphate precipitation, gel filtration, and ion exchange chromatography, with an overall recovery of 25.9%. The purified enzyme hada 70 kDa molecular weight (MW) confirmed by SDS-PAGE gel analysis. The maximum enzyme activity was reported at 55 °C and pH 7.0. Xylanase activity and stability were improved in the presence of 30% (v/v) n-dodecane, iso-octane, n-decane, and cyclohexane (7 days). The enzyme activity was improved by Co2+, EDTA, and Triton-X-100 while vigorously repressed by Hg2+ and Cu2+. The purified enzyme showed 1.473 mg/mL Km and 654.017 µg/mL/min Vmax values. The distinctive assets of the isolate verified the potential application in the field of biomass conversion into fuel and other industrial processes. Organic solvent-tolerant xylanases can be used for concurrent saccharification and bioethanol production, the amplification of intoxicating beverages, and the fermenting industry.

Paecilomyces variotii xylanase production, purification and characterization with antioxidant xylo-oligosaccharides production

Paecilomyces variotii xylanase was, produced in stirred tank bioreactor with yield of 760 U/mL and purified using 70% ammonium sulfate precipitation and ultra-filtration causing 3.29-fold purification with 34.47% activity recovery. The enzyme purity was analyzed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirming its monomeric nature as single band at 32 KDa. Zymography showed xylan hydrolysis activity at the same band. The purified enzyme had optimum activity at 60 °C and pH 5.0. The pH stability range was 5-9 and the temperature stability was up 70 °C. Fe²⁺and Fe³⁺ exhibited inhibition of xylanase enzyme while Cu²⁺, Ca²⁺, Mg²⁺ and Mn²⁺ stimulated its activity. Mercaptoethanol stimulated its activity; however, Na₂-EDTA and SDS inhibited its activity. The purified xylanase could hydrolyze beechwood xylan but not carboxymethyl cellulose (CMC), avicel or soluble starch. Paecilomyces variotii xylanase K_m and V_max for beechwood were determined to be 3.33 mg/mL and 5555 U/mg, respectively. The produced xylanase enzyme applied on beech xylan resulted in different types of XOS. The antioxidant activity of xylo-oligosaccharides increased from 15.22 to 70.57% when the extract concentration was increased from 0.1 to 1.5 mg/mL. The enzyme characteristics and kinetic parameters indicated its high efficiency in the hydrolysis of xylan and its potential effectiveness in lignocellulosic hydrolysis and other industrial application. It also suggests the potential of xylanase enzyme for production of XOS from biomass which are useful in food and pharmaceutical industries.

Efficient enzymatic saccharification of alkaline and ionic liquid-pretreated bamboo by highly active extremozymes produced by the co-culture of two halophilic fungi

Herein, we studied two strains of halophilic fungi (Aspergillus flavus and Aspergillus penicillioides) as potential potent sources of hydrolases under solid-state fermentation conditions. We found that the co-culture of these two fungal species was associated with maximal CMCase, FPase, xylanase, and β-xylosidase activity under optimized fermentation conditions. These enzymes functioned optimally at pH values from 9.0 to 10.0, at temperatures from 50 °C to 60 °C, and in the presence of 15-20% NaCl. These enzymes were also stable in metal salt solutions and the presence of ionic liquids. Reducing sugar yields following the cellulase-hemicellulase co-treatment of untreated, alkaline-pretreated, and ionic liquid-pretreated bamboo were higher than those associated with separate cellulase and hemicellulase treatments, thus confirming the synergistic activity of cellulase-hemicellulase co-treatment in the context of bamboo saccharification. These results indicate that these two fungi are promising hydrolase producers that can facilitate the bioconversion of bamboo biomass.

Enzymatic characterization of a novel thermostable and alkaline tolerant GH10 xylanase and activity improvement by multiple rational mutagenesis strategies

Thermo-alkaline xylanases are widely applied in paper pulping industry. In this study, a novel thermostable and alkaline tolerant GH10 xylanase (Xyn30Y5) gene from alkaliphilic Bacillus sp. 30Y5 was cloned and the surface-layer homology (SLH) domains truncated enzyme (Xyn30Y5-SLH) was expressed in Escherichia coli. The purified Xyn30Y5-SLH was most active at 70 °C and pH 7.0 and showed the highest specific activity of 349.4 U mg^-1. It retained more than 90% activity between pH 6.0 to 9.5 and was stable at pH 6.0-10.0. To improve the activity, 47 mutants were designed based on eight rational strategies and 21 mutants showed higher activity. By combinatorial mutagenesis, the best mutant 3B demonstrated specific activity of 1016.8 U mg^-1 with a doubled catalytic efficiency (k_cat/K_m) and RA60_1/2h value, accompanied by optimal pH shift to 8.0. The molecular dynamics simulation analysis indicated that the increase of flexibility of α5 helix and loop7 located near to the catalytic residues is likely responsible for its activity improvement. And the decrease of flexibility of the most unstable regions is vital for the thermostablity improvement. This work provided not only a novel thermostable and alkaline tolerant xylanase with industrial application potential but also an effective mutagenesis strategy for xylanase activity improvement.

Cloning, expression and characterization of C. crescentus xynA2 gene and application of Xylanase II in the deconstruction of plant biomass

Biotechnology offers innovative alternatives for industrial bioprocesses mainly because it uses enzymes that biodegrade the hemicellulose releasing fermentable sugars. Caulobacter crescentus (C. crescentus) has seven genes responsible for xylanolytic cleavage, 5 to β-xylosidases (EC 3.2.1.37) and 2 for endoxylanases, like xynA2 (CCNA_03137) that encodes Xylanase II (EC 3.2.1.8) of the glycohydrolases-GH10 group. The xynA2 gene was amplified by PCR, cloned into the pTrcHisA vector e efficiently overexpressed in E. coli providing a His-tag fusion protein. Recombinant xylanase (XynA2) was purified by affinity chromatography using a nickel sepharose column and exhibited a single 43 kDa band on SDS-PAGE gel. XynA2 showed an optimum alkaline pH (8) and stability at alkaline pH for 24 h. Although C. crescentus is mesophilic, XynA2 has optimum temperature of 60 °C and is thermo-resistance at 65 °C. XynA maintains 66% of the enzymatic activity at high temperatures (90 °C) without being denatured.The enzyme displayed a xylanolitic activity free of cellulase to xylan from beechwood and it was not inhibited in the presence of 50 μmol mL^-1 of xylose. In addition, dithiothreitol (DTT) induced XynA2 activity, as it improved its kinetic parameters by lowering the K_M (5.78 μmol mL^-1) and increasing the K_Cat/K_M ratio (1.63 U s^-1). Finally, C. crescentus XynA2 efficiently hydrolyzed corn straw with high release of reducing sugars that can be applied in different branches of the industry.

Alkaline Active Hemicellulases

Xylan and mannan are the two most abundant hemicelluloses, and enzymes that modify these polysaccharides are prominent hemicellulases with immense biotechnological importance. Among these enzymes, xylanases and mannanases which play the vital role in the hydrolysis of xylan and mannan, respectively, attracted a great deal of interest. These hemicellulases have got applications in food, feed, bioethanol, pulp and paper, chemical, and beverage producing industries as well as in biorefineries and environmental biotechnology. The great majority of the enzymes used in these applications are optimally active in mildly acidic to neutral range. However, in recent years, alkaline active enzymes have also become increasingly important. This is mainly due to some benefits of utilizing alkaline active hemicellulases over that of neutral or acid active enzymes. One of the advantages is that the alkaline active enzymes are most suitable to applications that require high pH such as Kraft pulp delignification, detergent formulation, and cotton bioscouring. The other benefit is related to the better solubility of hemicelluloses at high pH. Since the efficiency of enzymatic hydrolysis is often positively correlated to substrate solubility, the hydrolysis of hemicelluloses can be more efficient if performed at high pH. High pH hydrolysis requires the use of alkaline active enzymes. Moreover, alkaline extraction is the most common hemicellulose extraction method, and direct hydrolysis of the alkali-extracted hemicellulose could be of great interest in the valorization of hemicellulose. Direct hydrolysis avoids the time-consuming extensive washing, and neutralization processes required if non-alkaline active enzymes are opted to be used. Furthermore, most alkaline active enzymes are relatively active in a wide range of pH, and at least some of them are significantly or even optimally active in slightly acidic to neutral pH range. Such enzymes can be eligible for non-alkaline applications such as in feed, food, and beverage industries.This chapter largely focuses on the most important alkaline active hemicellulases, endo-β-1,4-xylanases and β-mannanases. It summarizes the relevant catalytic properties, structural features, as well as the real and potential applications of these remarkable hemicellulases in textile, paper and pulp, detergent, feed, food, and prebiotic producing industries. In addition, the chapter depicts the role of these extremozymes in valorization of hemicelluloses to platform chemicals and alike in biorefineries. It also reviews hemicelluloses and discusses their biotechnological importance.

Heterologous expression and characterization of a xylanase and xylosidase from white rot fungi and their application in synergistic hydrolysis of lignocellulose

Endo-xylanase and β-xylosidase are the major enzymes for hemicellulose hydrolysis, which play a significant role in biomass conversion. In our previous work, the white-rot fungi Pleurotus ostreatus HAUCC 162 and Irpex lacteus CD2 were demonstrated to have strong ability in lignocellulose degradation, and the related lignin degradation enzymes were characterized. However, little was known about their hemicellulases. In this work, a novel endo-1, 4-xylanase and a β-xylosidase from Pleurotus ostreatus HAUCC 162 and Irpex lacteus CD2 were heterologously expressed and characterized. The optima of pH and temperature were 5.0 and 55 °C for rXyn162, and 6.5 and 30 °C for rXylCD2. rXyn162 showed high tolerance to metal ions such as Ca²⁺, Cr³⁺, Zn²⁺, Na⁺, and Al³⁺. The recombinant rXyn162 and rXylCD2 exhibited synergistic hydrolysis of oat spelts xylan and sodium hydroxide pretreated cornstalk (SHPC), where the degree of synergy (DS) was 2.26 for SHPC hydrolysis. MALDI-TOF-MS and HPLC analysis showed that xylooligosaccharides (XOS) with small degrees of polymerization (DP2-DP4) were the major XOS hydrolyzate during SHPC degradation by rXyn162 and rXylCD2. In addition, rXyn162 and rXylCD2 could efficiently improve the hydrolysis of SHPC by commercial cellulase. The present study suggested the potential application of rXyn162 and rXylCD2 in the field of biomass pretreatment and biofuel production.

A New record of four Penicillium species isolated from Agarum clathratum in Korea

Agarum clathratum, brown algae, play important ecological roles in marine ecosystem, but can cause secondary environment pollution when they pile up on the beach. In order to resolve the environment problem by A. clathratum, we focus to isolate and identify Penicillium because many species are well known to produce extracellular enzymes. A total of 32 Penicillium strains were isolated from A. clathratum samples that collected from 13 sites along the mid-east coast of Korea in summer. They were identified based on morphological characters and phylogenetic analysis using β-tubulin DNA sequences as well as a combined dataset of β-tubulin and calmodulin. A total of 32 strains were isolated and they were identified to 13 Penicillium species. The commonly isolated species were Penicillium citrinum, P. roseomaculatum, and Penicillium sp. Among 13 Penicillium species, four species - P. bilaiae, P. cremeogriseum, P. madriti, and P. roseomaculatum - have not been previously recorded in Korea. For these four new species records to Korea, we provide morphological characteristics of each strain.

Thermoresistant xylanases from Trichoderma stromaticum: Application in bread making and manufacturing xylo-oligosaccharides

The enzymes Xyl1 and Xyl2 from T. stromaticum were purified and identified by mass spectrometry (MALDI-TOF/MS). Xyl1 contained three proteins with similarity to xylanase family 10, 62 and anarabinofuranosidase of the Trichoderma genus and Xyl2 contained a protein with similarity to endo-1,4-β-xylanase. High xylanase activity was found at 50°C for Xyl1 and 60°C for Xyl2 and pH 5.0 for both, retaining more than 80% of activities for one hour at 60°C and pH 5-8. Ag²⁺ and β-mercaptoethanol increased while SDS and EDTA inhibited the xylanase activity of both Xyl1 and Xyl2 extracts. The Km and V_max values for purified Xyl2 were 9.6mg/mL and 28.57μmol/min/mg, respectively. In application tests, both Xyl1 and Xyl2 were effective in degrading beechwood xylan to produce xylo-oligosaccharides. In baking, adding Xyl1 increased the softness and volume of wheat bread and whole grain bread, qualities increasingly desired by consumers in this segment.

Discovery and Characterization of a Thermostable and Highly Halotolerant GH5 Cellulase from an Icelandic Hot Spring Isolate

With the ultimate goal of identifying robust cellulases for industrial biocatalytic conversions, we have isolated and characterized a new thermostable and very halotolerant GH5 cellulase. This new enzyme, termed CelDZ1, was identified by bioinformatic analysis from the genome of a polysaccharide-enrichment culture isolate, initiated from material collected from an Icelandic hot spring. Biochemical characterization of CelDZ1 revealed that it is a glycoside hydrolase with optimal activity at 70°C and pH 5.0 that exhibits good thermostability, high halotolerance at near-saturating salt concentrations, and resistance towards metal ions and other denaturing agents. X-ray crystallography of the new enzyme showed that CelDZ1 is the first reported cellulase structure that lacks the defined sugar-binding 2 subsite and revealed structural features which provide potential explanations of its biochemical characteristics.

Newly Isolated Penicillium ramulosum N1 Is Excellent for Producing Protease-Resistant Acidophilic Xylanase

Penicillium ramulosum N1 was isolated from decaying wood. This strain produces extracellular xylanases and cellulases. The highest activities of xylanases (250 U/ml) and carboxymethyl cellulose (CMCase; 6.5 U/ml) were produced when 1% barley straw was added as a carbon source. The optimum temperature and pH for xylanase activity was 55 and 3.0 °C, respectively. The xylanases exhibited strong protease resistance. CMCase revealed maximum activities at pH 3.0 and in the range of 60-70 °C. Filter paper activity was optimally active at pH 5.0 and 55 °C. The zymograms produced by the SDS-PAGE resolution of the crude enzymes indicated that there are four bands of protein with xylanase activity and three bands of proteins with endoglucanase. The results revealed that P. ramulosum N1 is a promising acidophilic and protease-resistant xylanase-producing microorganism that has great potential to be used in animal feed and food industry applications.

Cellulolytic and xylanolytic potential of high β-glucosidase-producing Trichoderma from decaying biomass

Availability, cost, and efficiency of microbial enzymes for lignocellulose bioconversion are central to sustainable biomass ethanol technology. Fungi enriched from decaying biomass and surface soil mixture displayed an array of strong cellulolytic and xylanolytic activities. Strains SG2 and SG4 produced a promising array of cellulolytic and xylanolytic enzymes including β-glucosidase, usually low in cultures of Trichoderma species. Nucleotide sequence analysis of internal transcribed spacer 2 (ITS2) region of rRNA gene revealed that strains SG2 and SG4 are closely related to Trichoderma inhamatum, Trichoderma piluliferum, and Trichoderma aureoviride. Trichoderma sp. SG2 crude culture supernatant correspondingly displayed as much as 9.84 ± 1.12, 48.02 ± 2.53, and 30.10 ± 1.11 units mL(-1) of cellulase, xylanase, and β-glucosidase in 30 min assay. Ten times dilution of culture supernatant of strain SG2 revealed that total activities were about 5.34, 8.45, and 2.05 orders of magnitude higher than observed in crude culture filtrate for cellulase, xylanase, and β-glucosidase, respectively, indicating that more enzymes are present to contact with substrates in biomass saccharification. In parallel experiments, Trichoderma species SG2 and SG4 produced more β-glucosidase than the industrial strain Trichoderma reesei RUT-C30. Results indicate that strains SG2 and SG4 have potential for low cost in-house production of primary lignocellulose-hydrolyzing enzymes for production of biomass saccharides and biofuel in the field.

Novel xylanases from Simplicillium obclavatum MTCC 9604: comparative analysis of production, purification and characterization of enzyme from submerged and solid state fermentation

The production of extracellular xylanase by a newly isolated fungus Simplicillium obclavatum MTCC 9604 was studied in solid-state and submerged fermentation. Multiple xylanases and endoglucanases were produced by the strain during growth on wheat bran in solid state fermentation (SSF). A single xylanase isoform was found to be produced by the same fungus under submerged fermentation (SF) using wheat bran as sole carbon source. Enzyme activity, stability and the protein yield were much higher in SSF than SF. The two dimensional zymogram of the crude enzyme indicated the presence of six isoforms with different pI values starting from pH 3–10. The optimum temperature and pH for the partially purified xylanase activity were 50°C and pH 5.0 respectively; xylanase enzymes exhibited remarkable stability over a broad pH range and the temperature range of 30-60°C which has great potential to be used in biofuels, animal feed and food industry applications.

Production, purification, and characterization of a major Penicillium glabrum xylanase using Brewer's spent grain as substrate

In recent decades, xylanases have been used in many processing industries. This study describes the xylanase production by Penicillium glabrum using brewer's spent grain as substrate. Additionally, this is the first work that reports the purification and characterization of a xylanase using this agroindustrial waste. Optimal production was obtained when P. glabrum was grown in liquid medium in pH 5.5, at 25 °C, under stationary condition for six days. The xylanase from P. glabrum was purified to homogeneity by a rapid and inexpensive procedure, using ammonium sulfate fractionation and molecular exclusion chromatography. SDS-PAGE analysis revealed one band with estimated molecular mass of 18.36 kDa. The optimum activity was observed at 60 °C, in pH 3.0. The enzyme was very stable at 50 °C, and high pH stability was verified from pH 2.5 to 5.0. The ion Mn(2+) and the reducing agents β -mercaptoethanol and DTT enhanced xylanase activity, while the ions Hg(2+), Zn(2+), and Cu(2+) as well as the detergent SDS were strong inhibitors of the enzyme. The use of brewer's spent grain as substrate for xylanase production cannot only add value and decrease the amount of this waste but also reduce the xylanase production cost.

Production of alkaline cellulase by fungi isolated from an undisturbed rain forest of peru

Alkaline cellulase producing fungi were isolated from soils of an undisturbed rain forest of Peru. The soil dilution plate method was used for the enumeration and isolation of fast growing cellulolytic fungi on an enriched selective medium. Eleven out of 50 different morphological colonies were finally selected by using the plate clearing assay with CMC as substrate at different pH values. All 11 strains produced cellulases in liquid culture with activities at alkaline pH values without an apparent decrease of them indicating that they are true alkaline cellulase producers. Aspergillus sp. LM-HP32, Penicillium sp. LM-HP33, and Penicillium sp. LM-HP37 were the best producers of FP cellulase (>3 U mL⁻¹) with higher specific productivities (>30 U g⁻¹ h⁻¹). Three strains have been found suitable for developing processes for alkaline cellulase production. Soils from Amazonian rain forests are good sources of industrial fungi with particular characteristics. The results of the present study are of commercial and biological interest. Alkaline cellulases may be used in the polishing and washing of denim processing of the textile industry.

[Isolation and characterization of an alkaline xylanasefrom a newly isolated Bacillus sp. QH14]

Twenty-fivealkaline xylanase producing strains were isolated from Qinghai Lake side soil samples. Among these strains, QH14 produced 648.79 U/mLxylanase, and the enzymatic specific activity was 1148.56 U/mg after purification. This alkaline xylanase producing strain belongs to genus Bacillus based on16S rDNA sequencing analysis and then was designated as Bacillus sp. QH14. The alkalinexylanaseencoding gene, XynQH14, was cloned from Bacillus sp. QH14 and expressed in Escherichiacoli BL21 (DE3). The specific activity of the recombinant xylanase XynQH14 was 700.47 Umg-1 after purification by Ni-NTA affinity chromatography. The optimal temperature and pH of XynQH14 were 60℃ and pH9.2, respectively. Its activity was 50% of initial activity after incubation at 55 ℃ for 1h, 80% at pH7-11 at 37 ℃ for 24 h, and 31.02% at pH11 at 50℃ after 24 h, indicating that XynQH14 isthermostable and alkali-stable. These properties ofXynQH14 suggest its favorable potential applications in pulp and paper industries.

Studies on an alkali-thermostable xylanase from Aspergillus fumigatus MA28

An alkalitolerant fungus, Aspergillus fumigatus strain MA28 produced significant amounts of cellulase-free xylanase when grown on a variety of agro-wastes. Wheat bran as the sole carbon source supported higher xylanase production (8,450 U/L) than xylan (7,500 U/L). Soybean meal was observed to be the best nitrogen source for xylanase production (9,000 U/L). Optimum medium pH for xylanase production was 8 (9,800 U/L), though, significant quantities of the enzyme was also produced at pH 7 (8,500 U/L), 9 (8,200 U/L) and 10 (4,600 U/L). The xylanase was purified by ammonium sulphate precipitation and carboxymethyl cellulose chromatography, and was found to have a molecular weight of 14.4 kDa with a V(max) of 980 μmol/min/mg of protein and a K(m) of approximately 4.9 mg/mL. The optimum temperature and pH for enzyme activity was 50 °C and pH 8, respectively. However, the enzyme also showed substantial residual activity at 60-70 °C (53-75%) and at alkaline pH 8-9 (56-88%).

Alkalistable endo-β-1,4-xylanase production from a newly isolated alkalitolerant Penicillium sp. SS1 using agro-residues

Thermostable and alkalitolerant xylanases have got intense research focus due to their vast applications in various industries including pulp and paper, food, feed, textile, biofuel, etc. In the present investigation, a Penicillum sp. SS1 isolated from degrading woody material was found to produce moderately thermoactive and alkalistable endo-β-1,4-xylanase (xylanase). Maximum xylanase production was observed after fourth day of fermentation (43.84 IU/ml). The organism produced substantial quantities of xylanase using agricultural residues like wheat bran (20.6 IU/ml), rice bran (21.8 IU/ml) and sawdust (10.7 IU/ml) as carbon sources. The enzyme preparation was totally free of filter paper activity (FPase) and possessed negligible carboxymethyl cellulase (CMCase) activity; this could be an important feature of enzyme if the intended application of enzyme is in pulp and paper industries. Among nitrogen sources examined, yeast extract supported maximum xylanase production (45.74 IU/ml), and was followed by soybean meal (22.2 IU/ml) and ammonium sulphate (20 IU/ml). Maximum xylanase production was observed at initial medium pH 9 (25.6 IU/ml); however, at pH 8 and 10 also significantly high enzyme titre was observed (24 and 21.2 IU/ml, respectively). Thus, Penicillium sp. SS1 displayed capability of growing and producing xylanase at high alkaline pH (8-10). Maximum xylanase activity was reported at 50 °C, however, significantly high activity was observed at 60 °C (65.4%), however, at 70-80 °C activity was lost considerably. At 50-60 °C the enzyme retained very high activity up to 30-60 min (91-100%), however, prolonged incubation (90 min) caused considerable activity reduction (residual activity 63-68%).

Purification and characterization of two thermostable xylanases from Malbranchea flava active under alkaline conditions

Two xylanases, MFX I and MFX II, from the thermophilic fungus Malbranchea flava MTCC 4889 with molecular masses of 25.2 and 30kDa and pIs of 4.5 and 3.7, respectively were purified to homogeneity. The xylanases were optimally active at pH 9.0 and at 60 degrees C, exhibited a half-life of 4h at 60 degrees C, and showed distinct mode of action and product profiles when applied to birchwood, oat spelt, and larchwood xylan, and to wheat and rye arabinoxylan. The xylanases were most active on larchwood xylan with K(m) values of 1.25 and 3.7mg/ml. K(cat)/K(m) values suggested that the xylanases preferentially hydrolyzed rye arabinoxylan. LC-MS/MS (liquid chromatography/mass spectrometry) analysis of tryptic digests of MFX I and MFX II revealed similarity with known fungal xylanases and suggests that that they belonged to the GH 11 and 10 glycosyl hydrolase super families, respectively. These xylanases can potentially be used in enzyme-assisted bleaching of the pulp derived from agro-residues, as well as production of xylooligosaccharides for pre-biotic functional food applications.

High-level production of a thermoacidophilic beta-glucosidase from Penicillium citrinum YS40-5 by solid-state fermentation with rice bran

A high yield of beta-glucosidase (EC 3.2.1.21) of 159.1 U/g-solid activity on 4-nitrophenyl beta-d-glucopyranoside (pNPG) was achieved by rice bran-based solid-state fermentation (SSF) of the recently characterized fungus Penicillium citrinum YS40-5. The enzyme was both thermophilic and acidophilic at the optimized temperature and pH of 70 degrees C and 5.0, respectively. Over 95% of the original beta-glucosidase activity was maintained after a prolonged storage at ambient temperature for 4 weeks. The kinetic parameters V(max), K(m) and K(I) were 85.93 U/mg, 1.2 mM and 17.59 mM with pNPG, and 72.49 U/mg, 32.17 mM and 8.29 mM with cellobiose, respectively. The protein band with beta-glucosidase activity was characterized by native PAGE followed by MUG-zymogram analysis, and its identity confirmed by nanoLC-MS/MS. A 3.43-fold synergistic effect by combining this beta-glucosidase with Trichoderma reesei cellulases was observed, indicating this enzyme could potentially be used for improving the efficiency of cellulosic bioconversion.

In vitro renaturation of alkaline family G/11 xylanase via a folding intermediate: alpha-crystallin facilitates refolding in an ATP-independent manner

In this study, alkaliphilic family G/11 xylanase from alkali-tolerant filamentous fungi Penicillium citrinum MTCC 6489 was used as a model system to gain insight into the molecular aspects of unfolding/refolding of alkaliphilic glycosyl hydrolase protein family. The intrinsic protein fluorescence suggested a putative intermediate state of protein in presence of 2 M guanidium hydrochloride (GdmCl) with an emission maximum of 353 nm. Here we studied the refolding of GdmCl-denatured alkaline xylanase in the presence and the absence of a multimeric chaperone protein alpha-crystallin to elucidate the molecular mechanism of intramolecular interactions of the alkaliphilic xylanase protein that dictates its extremophilic character. Our results, based on intrinsic tryptophan fluorescence and hydrophobic fluorophore 8-anilino-1- naphthalene sulfonate-binding studies, suggest that alpha-crystallin formed a complex with a putative molten globule-like intermediate in the refolding pathway of xylanase in an ATP-independent manner. A 2 M GdmCl is sufficient to denature alkaline xylanase completely. The hydrodynamic radius (R(H)) of a native alkaline xylanase is 4.0, which becomes 5.0 in the presence of 2 M GdmCl whereas in presence of the higher concentration of GdmCl R(H) value was shifted to 100, indicating the aggregation of denatured xylanase. The alpha-crystallin.xylanase complex exhibited the recovery of functional activity with the extent of approximately 43%. Addition of ATP to the complex did not show any significant effect on activity recovery of the denatured protein.

Gene cloning, expression, and characterization of a thermostable xylanase from Nesterenkonia xinjiangensis CCTCC AA001025

An endo-beta-1,4-xylanase-encoding gene, xyn11NX, was cloned from Nesterenkonia xinjiangensis CCTCC AA001025 and expressed in Escherichia coli. The gene encoded a 192-amino acid polypeptide and a putative 50-amino acid signal peptide. The deduced amino acid sequence exhibited a high degree of similarity with the xylanases from Streptomyces thermocyaneoviolaceus (68%) and Thermobifida fusca (66%) belonging to glycoside hydrolase family 11. After purification to homogeneity, the recombinant Xyn11NX exhibited optimal activity at pH 7.0 and 55 degrees C and remained stable at weakly acidic to alkaline pH (pH 5.0-11.0). The enzyme was thermostable, retaining more than 80% of the initial activity after incubation at 60 degrees C for 1 h and more than 40% of the activity at 90 degrees C for 15 min. The K (m) and V (max) values for oat spelt xylan and birchwood xylan were 16.08 mg ml(-1) and 45.66 micromol min(-1) mg(-1) and 9.22 mg ml(-1) and 16.05 micromol min(-1) mg(-1), respectively. The predominant hydrolysis products were xylobiose and xylotriose when using oat spelt xylan or birchwood xylan as substrate.