Modification of the acetaldehyde concentration during alcoholic fermentation and effects on fermentation kinetics

We studied the kinetic effects of increasing the residual acetaldehyde concentration during alcoholic fermentation, especially during the stationary phase. We added this compound via pulse or continuous injections. The yeast response depended on the amount of acetaldehyde added: high concentrations inhibited fermentation while low concentrations led to stimulation. When regular small additions were made, up to 100 mM acetaldehyde could be added and this caused a very significant drop in the fermentation duration. We also modulated the acetaldehyde concentration by modifying the alcohol dehydrogenase-catalyzed reaction. Two approaches were tested (i) adding aldehydes (propanal and furfural) that competitively inhibited the reduction of acetaldehyde and (ii) adding electron acceptors that reduced the quantity of NADH available. Several possible mechanisms responsible for (i) the impact of acetaldehyde on fermentation kinetics and (ii) the modulation of the residual acetaldehyde concentration are discussed.