SCREENING OF ENZYMATIC ACTIVITIES IN NON-SACCHAROMYCESCIDER YEASTS

Abstract

ABSTRACT The activities of polygalacturonase, pectin lyase, β-glucosidase, β-xylosidase and protease were determined using solid media in 420 wild non-Saccharomyces cider strains identified by internal transcribed spacer-restriction fragment length polymorphism. The identified species corresponded to Hanseniaspora valbyensis, Hanseniaspora uvarum, Hanseniaspora osmophila, Metschnikowia pulcherrima, Candida parapsilosis and Pichia guilliermondii. The most common activity exhibited was that of β-glucosidase (33%), with all the analyzed species having some strains able to develop this activity. Strains of M. pulcherrima showed the greatest capacity to produce β-glucosidase and protease. β-xylosidase was detected in 17 yeast strains belonging to the genera Hanseniaspora, Pichia and Metschnikowia. All of the tested species have some strains with the capacity to develop β-xylosidase activity, except for C. parapsilosis. No strains were able to secrete pectin lyase, while polygalacturonase activity was observed in eight Hanseniaspora strains. Only two strains, belonging to the species H. uvarum and M. pulcherrima, developed three enzymatic activities, namely β-glucosidase, β-xylosidase and protease. PRACTICAL APPLICATIONS The non-Saccharomyces yeasts are very interesting in cider making because of the low level of ethanol in cider. In this paper, it is demonstrated that the yeast isolated from Asturian cider represents a source of several enzymes, which have capacity to release flavor compounds. In this sense non-Saccharomyces strains are being used as inoculated cultures to ferment apple pomace and apple must, with the aim of enhancing the aroma and flavor of the products.