HETEROLOGOUS PRODUCTION IN SACCHAROMYCES-CEREVISIAE OF DIFFERENT ASPERGILLUS-NIDULANS XYLANASES OF POTENTIAL INTEREST IN ENOLOGY

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 gl ucose 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 singl e chromatographic step and then physico-chemically characterised. The yeast derived enzymes had the same enzymatic and biochemical propertie s as the fungal xylanases (ie molecular weights, pI values, pH and tem perature optima, K-m Michaelis constants and pH and temperature stabil ities). The heterologously produced enzymes retained maximum activity in the presence of 10% (w/v) glucose or 10% (w/v) fructose, concentrat ions normally found in musts. However, ethanol at 12% (v/v) caused inh ibitions of 20% for X-22 and X-24 and 48% for X-34. (C) 1998 Society o f Chemical Industry.