Novel pH-Stable Glycoside Hydrolase Family 3 β-Xylosidase from Talaromyces amestolkiae: an Enzyme Displaying Regioselective Transxylosylation

Abstract

This paper reports on a novel ␤-xylosidase from the hemicellulolytic fungus Talaromyces amestolkiae. The expression of this enzyme, called BxTW1, could be induced by beechwood xylan and was purified as a glycoprotein from culture supernatants. We characterized the gene encoding this enzyme as an intronless gene belonging to the glycoside hydrolase gene family 3 (GH3). BxTW1 exhibited transxylosylation activity in a regioselective way. This feature would allow the synthesis of oligosaccharides or other compounds not available from natural sources, such as alkyl glycosides displaying antimicrobial or surfactant properties. Regioselective transxylosylation, an uncommon combination, makes the synthesis reproducible, which is desirable for its potential industrial application. BxTW1 showed high pH stability and Cu 2؉ tolerance. The enzyme displayed a pI of 7.6, a molecular mass around 200 kDa in its active dimeric form, and K m and V max values of 0.17 mM and 52.0 U/mg, respectively, using commercial p-nitrophenyl-␤-D-xylopyranoside as the substrate. The catalytic efficiencies for the hydrolysis of xylooligosaccharides were remarkably high, making it suitable for different applications in food and bioenergy industries. P lant biomass represents the most abundant renewable energy resource available on earth. It is composed mainly of cellulose and hemicellulose, two polysaccharides that constitute the raw material for the so-called second-generation (2G) bioethanol industry. The production of this biofuel has received special attention in recent years because it is based on the use of nonfood sources of cellulosic biomass (1). It has been pointed out that energy crops should be restricted to metal-contaminated soils in order to avoid cultivation competition against the food industry (2, 3).In order to make the production of this biofuel economically viable, many modifications have been introduced into the industrial process in recent years. Among them, the strategy of combining enzymatic hydrolysis of lignocellulose with ethanol fermentation in a single process known as simultaneous saccharification and fermentation (SSF) is a significant step forward, but reduced production costs and improved yields are still necessary (1). Most studies have been using agricultural wastes as raw materials, usually after a physicochemical pretreatment to disrupt the lignocellulose structure to enhance cellulose and hemicellulose accessibility. Nevertheless, the industrial procedure currently used to produce 2G ethanol consists of fermenting glucose, which is enzymatically released from cellulose by using Saccharomyces cerevisiae as a biocatalyst (4). To increase process yields, hemicellulose hydrolysis and pentose fermentation are extremely relevant. Within this heterogeneous group of polysaccharides, xylans are most abundant in hardwoods and grass. They are composed of a backbone of ␤-1,4-linked D-xylopyranosyl units highly substituted with arabinofuranose, glucose, glucuronic or methyl-glucuronic acid, and acetyl side groups. The enz...

A snapshot of microbial diversity and function in an undisturbed sugarcane bagasse pile

“…The culturing experiments isolated the highly related T. ruber, T. amestolkiae, T. rugulosus, T. funiculosus and T. flavus, which all have very similar ITS sequences and appearances and are also anamorphs (or were renamed) to various Penicillium species [57]. While, T. piceus was recently shown to possess a novel lignocellulolytic enzyme system [58], T. amestolkiae produces diverse β-glucosidases [59,60], and T. funiculosus (also known as P. funiculosum) is used commercially to degrade xylan in animal feed [61], the biomass degrading capability of the other isolates has not been reported until now.…”

Prebiotic effect of xylooligosaccharides produced from birchwood xylan by a novel fungal GH11 xylanase

“…In a previous study, a screening for lignocellulolytic fungi was carried out and the perfect state of a Penicillium species, identified as Talaromyces amestolkiae, was selected for encoding a large number of cellulases and hemicellulases (Nieto-Dominguez et al, 2015). The work presented here reports the production, isolation and biochemical characterization of a novel endoxylanase from this fungus.…”

Immobilization and Stabilization of Beta-Xylosidases from Penicillium janczewskii

“…Probably, BXYL II is homotrimeric, with three 67 kDa subunits, as verified by the presence of a more intense band. The MW of BXYL II is similar to many fungal β-xylosidases which usually present MW above 100 kDa [29][30][31][32][33] but present MW higher than that of the BXYL I, whose native MW is 200 kDa [19].…”