Immobilization of S. cerevisiae and O. œni for the control of wine fermentation steps

Abstract

Controlling the speed of alcoholic (AF) and malolactic (MLF) fermentations in wine can be an important challenge for the production of certain short rotation wines for entry-level market segments. Immobilization techniques for Saccharomyces cerevisiae and Œnococcus œni, the microorganisms responsible for these fermentations, are widely studied for industrial applications. Indeed, these processes allow to accumulate biomass and thus to increase cell densities inducing high fermentation velocities. Recent works have shown the performance of MLF carried out with biofilms of O. œni, immobilized on various supports in a rich medium (MRSm: modified MRS broth with malic acid and fructose).

Our work shows the possibility of inducing the adhesion of O. œni and S. cerevisiae, alone or in co-culture, in low nutriment medium, on different materials already used in the winery environment, at the microplate scale, in static conditions. The quantities of attached biomass (CFU counts) are close for all the tested modalities at the end of the adhesion time (48h for S. cerevisiae and 72h for O. œni with one broth renewal). The inoculated supports are transferred after rinsing into tubes containing must or wine, depending on the application, and the progress of the fermentations is analysed. In most conditions, total sugars are below 5 g/l after 5 days of AF, and all malic acid in the substrate (about 4 g/l) is consumed in 10 to 15 days.

This immobilization model could be the first step towards a perfectly controlled industrial fermentation processes.