Heterologous production in Saccharomyces cerevisiae of different Aspergillus nidulans xylanases of potential interest in oenology

Three Aspergillus nidulans endo-beta-(1,4)-xylanases (X-22, X-24 and X-34) have been produced in Saccharomyces cerevisiae laboratory strains. In fermenter cultivation, the resulting strains were able to secrete the heterologous xylanases when grown in minimal medium containing glucose as carbon source, yielding production levels between 0.5 and 1.0 U ml(-1). From such a culture, the xylanases were purified in a single chromatographic step and then physico-chemically characterised. The yeast derived enzymes had the same enzymatic and biochemical properties as the fungal xylanases (ie molecular weights, pI values, pH and temperature optima, K-m Michaelis constants and pH and temperature stabilities). The heterologously produced enzymes retained maximum activity in the presence of 10% (w/v) glucose or 10% (w/v) fructose, concentrations normally found in musts. However, ethanol at 12% (v/v) caused inhibitions of 20% for X-22 and X-24 and 48% for X-34. (C) 1998 Society of Chemical Industry.