Nutrient depletion modifies celi wall adsorption activity of wine yeast.

There is wide evidence for the effects of nutrient depletion on fungal cell wall, as the pseudohyphal growth and the flocculation state in Saccharomyces cerevisiae. The present work aimed to describe the effect of carbon and nitrogen availability on parietal adsorption activity of selected wine yeasts, testing them in the presence of grape pigments. Eleven strains of S. cerevisiae - previously selected as wine starter also considering their different aptitude to adsorb grape pigments - and the control strains of S. cerevisiae BY4742 and Σ1278b were grown on (a) grape skin agar (1), containing black grape skin powder 4% and dextrose 5%, 2% or 0.1%, (b) synthetic low ammonium dextrose agar (2) supplemented with black grape skin powder 4% and containing dextrose 2% or 0.1%, and (c) yeast peptone dextrose agar as control medium. After incubation at 28°C for 10 days, strains were processed for their colour components by Photoshop CS (1), that gives low or high values for yeast able (dark biomass) or unable (light biomass) to adsorb coloured compounds, respectively. In the different growth conditions, the tested yeasts showed wide and significant differences for their colour components. In general, depletion in (a) nitrogen or in (b) carbon and nitrogen determines a decrease in the yeast adsorption activity. The relevant related literature and the present results are discussed considering, above all, the oenological consequences for wine starter selection. (1) Caridi A. et al. - Wine colour adsorption phenotype: an inheritable quantitative trait loci of yeasts. Journal of Applied Microbiology 103, 735-742, 2007. (2) Zaragoza O., Gancedo J.M. - Pseudohyphal growth is induced in Saccharomyces cerevisiae by a combination of stress and cAMP signalling. Antonie van Leeuwenhoek 78, 187-194, 2000. This research was supported by Calabria Region, Research Fund APQ, Action 3, leader winery: Caparra & Siciliani.