Purification, biochemical characterization and structural modelling of alkali-stable β-1,4-xylan xylanohydrolase from Aspergillus fumigatus R1 isolated from soil

Abstract

BackgroundAspergillus fumigatus R1 produced xylanase under submerged fermentation which degrades the complex hemicelluloses contained in agricultural substrates. Xylanases have gained considerable attention because of their tremendous applications in industries. The purpose of our study was to purify xylanase and study its biochemical properties. We have predicted the secondary structure of purified xylanase and evaluated its active site residues and substrate binding sites based on the global and local structural similarity.ResultsVarious microorganisms were isolated from Puducherry soil and screened by Congo-red test. The best isolate was identified to be Aspergillus fumigatus R1. The production kinetics showed the highest xylanase production (208 IU/ml) by this organism in 96 h using 1 % rice bran as the only carbon source. The purification of extracellular xylanase was carried out by fractional ammonium sulphate precipitation (30–55 %), followed by extensive dialysis and Bio-Gel P-60 Gel-filtration chromatography. The enzyme was purified 58.10 folds with a specific activity of 38196.22 IU/mg. The biochemical characterization of the pure enzyme was carried out for its optimum pH and temperature (5.0 and 500C), pH and temperature stability, molecular mass (Mr) (24.5 kDa) and pI (6.29). The complete sequence of protein was obtained by mass spectrometry analysis. Apparent Km and Vmax values of the xylanase for birchwood xylan were 11.66 mg/ml and 87.6 μmol min−1 mg−1 respectively.ConclusionPurified xylanase was analyzed by mass-spectrometry which revealed 2 unique peptides. Xylanase under current study showed significant production using agricultural residues and a broad range of pH stability in the alkaline region. Xylanase produced by Aspergillus fumigatus R1 could serve as the enzyme of choice in industries.

Characterization of a novel xylanase from Aspergillus flavus with the unique properties in production of xylooligosaccharides

“…Similar to the xylanase from A. niger [23], the AfXynB showed its highest activity in a neutral pH (pH 7.5), while most other reported xylanases were active in a weakly acidic pH ranged from 5.0 to 7.0 [19,22,25]. Besides, the AfXynB was found stable to retain more than 82.3% of its initial activity within pH 4.0-9.5, which is similar to the crude xylanase from A. nidulans [20].…”

“…In contrast, most other reported xylanases from Aspergillus sp. are usually only stable in a much more narrow range of pH values, such as those from A. flavus (pH 4.5–6.5) , A. niger (pH 4.0–6.5) and A. fumigatus (pH 7.0–9.0) . Based on these results, AfXynB could be considered to be more suitable for application in a neutral environment than those xylanases mentioned above.…”

“…since they are capable of producing high levels of extracellular enzymes and can be cultivated very easily [20]. Although a great number of xylanases have been studied in different Aspergillus strains [21][22][23], few reports are available on the properties of the xylanases from A. flavus. Till date, only four xylanases from A. flavus had been purified and characterized, which had respective molecular mass at 14.0, 20.2, 28.5, and 35.0 kDa [24][25][26][27].…”

Xylanase production from Penicillium citrinum isolate HZN13 using response surface methodology and characterization of immobilized xylanase on glutaraldehyde-activated calcium-alginate beads

“…Penicillium citrinum isolate HZN13 was observed to possess globose conidia, septate hyphae and branched conidiophore after staining with lactophenol cotton blue. Several researchers have reported the isolation of xylanase-producing isolates like Aspergillus tubingensis FDHN1 from compost pit (Adhyaru et al 2015 ), Penicillium ramulosum N1 from decaying wood (Lin et al 2015 ), Aspergillus fumigatus isolate R1 (Deshmukh et al 2016 ) and P. citrinum xym2 from garden soil (Saha and Ghosh 2014 ).

Fig.

…”

Improvement in catalytic activity and thermostability of a GH10 xylanase and its synergistic degradation of biomass with cellulase

“…Common approaches involve mining new genetic resources from extreme environments, engineering the enzymes, and optimizing their application [8, 9]. Several xylanases from Aspergillus fumigatus R1 [10], Streptomyces coelicolor A3 [11], Aspergillus niger [12], and Bispora sp. MEY-1 [13] have high catalytic activities of 18,000 to 38,000 U/mg.…”