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

Abstract

A novel xylanase from the filamentous fungus Aspergillus flavus was purified and characterized as the β‐1, 4‐endoxylanase (designed as AfXynB) with a molecular mass (32.2 kDa), which is different from all of the previously reported xylanases from the same strain. AfXynB was optimally active at pH 7.5 and 55 °C, respectively. It was stable up to 50 °C within range of pH 4.0–9.5, and displayed an excellent tolerance to various cations, reagents, and proteases. AfXynB showed specific activity toward beechwood xylan but no detected activity toward CMC and pNP‐β‐D‐xylopyranoside. The xylanase is a typical endo‐xylanase; it could hydrolyze beechwood xylan to only yield xylobiose (X2) and xylopentaose (X5). Actually, this may be the first report for the endo‐xylanases that displayed such a unique hydrolytic property. These findings in the present study have great implications for its future applications of the novel xylanase.

An Eco-Friendly Production of a Novel and Highly Active Endo-1,4-beta-xylanase from Aspergillus clavatus

“…It can be assumed that during this time, the fungus absorbed all the easily assimilated nutrients from the culture medium and reached sufficient maturity to secrete large concentrations of complex enzymes, such as xylanases, in order to degrade and absorb complex nutrients from the culture medium. This result is similar to that obtained by Chen et al [32], who improved xylanase production by Aspergillus flavus after 5 days of cultivation. The same result was also observed by Menezes et al [33], who obtained the best xylanase activity by Aspergillus brasiliensis BLf1 and recombinant Aspergillus nidulans XynC A773 after 5 days of culture.…”

“…Also, it is possible that the ß-glucosidase showed some hydrolysis activity on xylotetraose and xylotriose, as previously observed by Zhou et al [48]. The xylobiose and xylotriose have gained much attention because of their use as a higher-value food supplement (prebiotic), promoting the proliferation of Bifidobacteria, a beneficial microorganism for human intestines and which reduces the risk of colon cancer [32,49].…”

“…Nowadays, xylobiose and xylotriose are the most common XOSs produced by the enzymatic hydrolysis of endo-xylanases [32,45]. However, the endo-1,4-beta-xylanase produced by A. clavatus exhibited a little different pattern of hydrolysis.…”

Bioprospecting of xylanase producing fungal strains: Multilocus phylogenetic analysis and enzyme activity profiling

“…These xylanases may have different biochemical properties and specific activity, which may impart stability over a broad range of pH and temperature [22]. Based on the quantity of enzyme secreted, production process, temperature, pH, and time, the xylanases from AUMS60 and AUMS64 show selectively better catalytic activity than those produced from Trichoderma koningii (810.7 U g −1 /30°C/7 days) [23] and other reports of xylanase production using corn cobs alone or in combination with other substrates from A. niger (10.5 U ml −1 ) and Aspergillus flavus (11.92 U ml −1 ) [24], Aspergillus flavus (65 U ml −1 ) [25], and Penicillium purpurogenum (84.61 U ml −1 , using delignified corn cobs) [7].…”

“…Xylanases secreted by AUMS60 (Xyn60) and AUMS64 (Xyn64A and Xyn64B) were comparable in size to various other xylanases produced by A. flavus (32.2 and 20.2 kDa) [25,26], A. terreus S9 (33 kDa) [27], A. fumigatus (20 kDa) [21] and Thermomyces lanuginosus VAPS-24 (20 kDa) [28]. Low molecular weight xylanases can easily penetrate the hydrolysis holes, alleviating the problem of xylan barrier (on lignin surface) toward bleaching chemicals and thus find huge applications in paper and pulp industry and provide a good opportunity for expression in defined hosts (E. coli, Saccharomyces cerevisiae, and Scheffersomyces stipitis) as per process requirement for increasing saccharification efficiencies of complex lignocelluloses [29].…”