Impact of the addition of electron acceptors on the by-products of alcoholic fermentation

In this study, we investigated the consequences of adding electron acceptors on the production of compounds involved in the maintenance of redox equilibrium in yeast during alcoholic fermentation: glycerol, succinate, acetate, malate, acetoin and butanediol. The various mechanisms involved are only fully functional in the stationary phase. They demonstrate in particular: (i) that in these conditions, the synthesis of glycerol serves more as a means of eliminating a surplus of reducing power than as a means of protection against osmotic pressure; (ii) the importance of the synthesis of acyloins, such as acetoin, followed by reduction to diols. The results obtained also provide information concerning the synthetic pathways for succinate and acetate. These reactions are important in the production of alcoholic drinks (particularly in wine production), because they concern compounds that affect the organoleptic qualities of the products. They may also be of value for the stereospecific synthesis of certain diol-like compounds.