Cultivation conditions preferable for yeast cells to be immobilized into poly(vinyl alcohol) and used in bottled sparkling wine production

Abstract

An effective approach to the improvement of the biochemical status of yeast cells before their immobilization was applied to develop a biocatalyst with a high level of cell metabolic activity and viability that could be used for sparkling wine production. According to the approach, the wine-containing medium (pH 3.0) routinely used for the accumulation of champagne yeast biomass under aerobic conditions was replaced by a semi-synthetic one (pH 5.6), usually applied for aerobic yeast growth. The variation of temperature and pH conditions of cell growth showed a modification of the fatty acid pool of yeasts and its importance for the further immobilization of cells into a poly(vinyl alcohol) cryogel. Measurement of the specific intracellular ATP concentration by the bioluminescent method revealed the growth phase favorable for yeast immobilization. The main characteristics of the sparkling wine obtained after four-week fermentation with application of both the free and immobilized cells were similar but, according to the detected energetic status, the viability level of the immobilized cells was considerably higher compared to the free yeast. The CO2 pressure accumulated in the bottles with immobilized cells (up to 500 kPa) after fermentation also appeared notably higher than in the bottles with free yeast.