Genetic improvement for technological traits of non-Saccharomyces wine yeasts

While Saccharomyces cerevisiae is the main species of wine production, other species have significant roles; interactions between the different species and their impacts on process efficiency and product quality need to be identified and evaluated [I]. At present, there is a growing demand for selected strains of non-Saccharomyces wine yeasts suitable to be used in association with Saccharomyces cerevisiae for grape juice fermentation [2J. Wine yeasts of the genus Hanseniaspora [3J and Schizosaccharomyces [4J perform alcoholic fermentation producing notably amounts of acetic acid and hydrogen sulphite and - for these attributes - usually they are not easily suitable in winemaking. Since they are ascosporogenous yeasts [5], as for Saccharomyces they could be processed via classical methods, such as micromanipulation, in order to improve their technological characteristics. The aim of this work was 10 consider the implications ofa new technique - easy, cheap and fastable to improve by genetic way technological traits in tvnv-Soccharomyces ascospore-producing wine yeasts. The new technique essentially consists in: I) inducing the production of ascospore using acetate agar, Gorodkowa agar, and Sabouraud agar; 2) inducing the lysis of the asci using zymolyase; 3) plating the serial dilutions in nutrient medium; 4) based on the morphological characteristics of colony and cell, collecting the descendants; 5) testing hydrogen sulphite and acetic acid production on BiGGY agar and Chalk agar; 6) selecting the best strains. A total of 12 strains of Schizosaccharomyces spp. and 35 strains of Hanseniaspora spp. were tested in order to identify strains able to produce enough amount of ascospores. Then, they were processed using both the new technique and the micromanipulation technique. In details, using the new technique a total of 35 descendants of Schizosaccharomyces and 29 descendants of Hanseniaspora were collected. An interesting biodi versity was observed both on BiGGY agar and Chalk agar, so validating the effectiveness of the proposed technique.