Malic Acid Consumption by Dry Immobilized Cells ofSchizosaccharomyces pombe

Abstract

Immobilized cells of <i>Schizosaccharomyces pombe</i> yeast were used for total or partial deacidification of grape must. All experiments were carried out using dry immobilized yeast cells instead of wet immobilized yeast cells as in previous works. Immobilized cells of <i>Schiz. pombe</i> were only used at the beginning of fermentation until partial or total consumption of L-malic acid. Immobilized cells were then removed from the fermentation tank and the must was re-inoculated with a commercial strain of <i>Saccharomyces cerevisiae</i> to achieve alcoholic fermentation. Experiments showed that in terms of kinetics, the high malate fermentation activity of the immobilized yeast cells was similar to that of the non-immobilized cells. Sensorial evaluation showed that the wines obtained using <i>Schiz. pombe</i> had a better organoleptic quality than the wine without deacidification. Analysis of some aromatic compounds (hydrogen sulfide, acetaldehyde, methanol, isopropanol, amyl and iso-amyl alcohols) at the end of the alcoholic fermentation did not show a significant difference in comparison to the control fermentation. Deacidification activity of immobilized yeast cells was maintained for at least 20 months after their encapsulation, at which point they were stored at 4°C. Alginate bead quality tests showed that immobilized cells could be recycled up to five times without liberation of yeast cells into wine must.