Applicability of enzymatic extracts obtained by solid state fermentation on grape pomace and orange peels mixtures in must clarification

Grape pomace, a residue produced in the wine industry, is becoming an environmental problem. By other hand enzymes extracts are products of great value in the wine making. In this work we evaluated applicability in must clarification of an enzyme extract produced by solid state fermentation on a mixture of grape pomace and orange peel. Before using the enzyme extracts, lyophilisation and different methods of protein precipitation were tested in order to concentrate exo-PG and xylanase. Our results showed that ethanol precipitation at −20 °C was the most adequate method, obtaining efficiencies of 50.2% and 39.2% for exo-PG and xylanase, respectively. This concentrated protein extract was used for clarification of must, giving a decrease of 97.5% respect to the initial turbidimetry after 40 h of incubation, which improved the clarification obtained with other commercial crude enzymes. Exo-PG and xylanase contained in our protein extracts were very stable at different temperatures, pH and in the presence of different cations. Finally, exo-PG and xylanase were partially purified by anion exchange chromatography on DEAE-cellulose column obtaining enrichments of 35.5- and 5.5-fold respectively over the culture supernatant. All these results suggested the promising application in juice and wine industries of the concentrated extracts with high levels of exo-PG and xylanase obtained by the proposed method.