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Xylanases play a crucial role in the hydrolysis of xylan-rich hemicelluloses and have wide industrial applications in the fuel, food, feed and pulp and paper industries. The production of these enzymes at low cost is of paramount importance for their commercial deployment. Moesziomyces antarcticus PYCC 5048 T and M. aphidis PYCC 5535 T were screened for their ability to produce xylanolytic enzymes when grown on D-xylose, xylan (beechwood) and brewery's spent grain (BSG). The extracellular crude extracts produced were characterized and tested in xylan hydrolysis. The yeasts produced xylanolytic enzymes without cellulolytic activity on all the substrates tested. The highest xylanase volumetric activity was obtained with M. aphidis PYCC 5535 T grown on BSG, reaching 518.2 U/ml, a value 8.4- and 4.7-fold higher than those achieved on xylan and D-xylose, respectively. The xylanase activities were characterized in relation to pH and temperature with optima at 4.5 and 50 °C, respectively. The extracts from both M. antarcticus PYCC 5048 T and M. aphidis PYCC 5535 T were used in xylan hydrolysis, producing D-xylose as the major end product (0.43 and 0.34-0.47 g D-xylose /g xylan , respectively, at 50 °C) and relatively low or no xylobiose accumulation (from no detection to 0.12 g D-xylobiose /g xylan at 50 °C).

International audience; Oomycetes are microorganisms that are distantly related to true fungi and many members of this phylum are major plant pathogens. Oomycetes express proteins that are able to interact with plant cell wall polysaccharides, such as cellulose. This interaction is thought to be mediated by carbohydrate-binding modules that are classified into CBM family 1 in the CAZy database. In this study, the two CBMs (1-1 and 1-2) that form part of the cell wall glycoprotein, CBEL, from Phytophthora parasitica have been submitted to detailed characterization, first to better quantify their interaction with cellulose and second to determine whether these CBMs can be useful for biotechnological applications, such as biomass hydrolysis. A variety of biophysical techniques were used to study the interaction of the CBMs with various substrates and the data obtained indicate that CBEL's CBM1-1 exhibits much greater cellulose binding ability than CBM1-2. Engineering of the family 11 xylanase from Talaromyces versatilis (TvXynB), an enzyme that naturally bears a fungal family 1 CBM, has produced two variants. The first one lacks its native CBM, whereas the second contains the CBEL CBM1-1. The study of these enzymes has revealed that wild type TvXynB binds to cellulose, via its CBM1, and that the substitution of its CBM by oomycetal CBM1-1 does not affect its activity on wheat straw. However, intriguingly the addition of CBEL during the hydrolysis of wheat straw actually potentiates the action of TvXynB variant lacking a CBM1. This suggests that the potentiating effect of CBM1-1 might not require the formation of a covalent linkage to TvXynB.