Characterization of the Highly Efficient Acid-Stable Xylanase and β-Xylosidase System from the Fungus Byssochlamys spectabilis ATHUM 8891 (Paecilomyces variotii ATHUM 8891).

Anastasia P Galanopoulou,Diomi Mamma,Dimitris G Hatzinikolaou,Irini Haimala,Daphne N Georgiadou

doi:10.3390/jof7060430

Abstract

Two novel xylanolytic enzymes, a xylanase and a β-xylosidase, were simultaneously isolated and characterized from the extracellular medium of Byssochlamys spectabilis ATHUM 8891 (anamorph Paecilomyces variotii ATHUM 8891), grown on Brewer’s Spent Grain as a sole carbon source. They represent the first pair of characterized xylanolytic enzymes of the genus Byssochlamys and the first extensively characterized xylanolytic enzymes of the family Thermoascaceae. In contrast to other xylanolytic enzymes isolated from the same family, both enzymes are characterized by exceptional thermostability and stability at low pH values, in addition to activity optima at temperatures around 65 °C and acidic pH values. Applying nano-LC-ESI-MS/MS analysis of the purified SDS-PAGE bands, we sequenced fragments of both proteins. Based on sequence-comparison methods, both proteins appeared conserved within the genus Byssochlamys. Xylanase was classified within Glycoside Hydrolase family 11 (GH 11), while β-xylosidase in Glycoside Hydrolase family 3 (GH 3). The two enzymes showed a synergistic action against xylan by rapidly transforming almost 40% of birchwood xylan to xylose. The biochemical profile of both enzymes renders them an efficient set of biocatalysts for the hydrolysis of xylan in demanding biorefinery applications.

Highlights

A consortium of xylan-degrading enzymes, functioning at elevated temperatures and extreme pH values, is essential for high-yield lignocellullose hydrolysis to fuel 2ndgeneration biorefinery applications [1,2]
The production of xylanolytic enzymes from B. spectabilis ATHUM 8891 is induced the presence of lignocellulosic substrates in the medium [17]
A potential role in ethanol production from lignocellulose has been identified for Thermoascaceae members [36], the majority of the studies in this area have mainly been focused on other fungal genera such as Fusarium and Neurospora spp

Summary

Introduction

A consortium of xylan-degrading enzymes, functioning at elevated temperatures and extreme pH values, is essential for high-yield lignocellullose hydrolysis to fuel 2ndgeneration biorefinery applications [1,2]. Endo-xylanases (EC 3.2.1.8) and β-xylosidases (EC 3.2.1.37) are two key hemicellulases that cleave the β-1,4 glycosidic linkage between two xylose units Their action is differentiated by their preference towards either internal bonds in the xylan backbone and high MW xylo-oligosaccharides (xylanases) or the non-reducing termini of short chain-length xylooligosaccharides (β-xylosidases). Both enzymes find additional specific applications in the food, pulp and paper industry, either as constituents of enzymatic cocktails or as individual enzymes [3]. Fungal hemicellulases are among the most efficient and robust, in terms of stability and activity ranges [1,5], with most of them being characterized from efficient plant biomass degraders within the ascomycete and basidiomycete genera [2,6]

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