Effect of extraction and enzymatic esterification of ethanol on glucose consumption by two Saccharomyces cerevisiae strains: a comparative study

Extractive alcoholic fermentations of high glucose concentrations (300 and 400 g dm^?3) using a flocculent (saké) and a non‐flocculent (DER24) Saccharomyces cerevisiae strain were compared. The introduction of a Rhizomucor miehei lipase, in the extractive fermentations of 300 g dm^?3 of glucose, increased the ethanol extraction due to its esterification with oleic acid, allowing complete glucose consumption at an organic solvent/fermentation medium phase ratio of 1. In these conditions, an increase of ethanol yield was observed. Total glucose consumption was also obtained in enzymatic extractive fermentations of 400 g dm^?3 of glucose, but only when oleic acid was added at the exponential growth phase. From the comparison of the extractive fermentation performances obtained using the two yeast strains it was observed that the flocculent strain led to a lower glucose metabolisation rate. This behaviour was related to the highest diffusional limitations that occur in the presence of flocs. The developed processes showed that the association of alcoholic fermentation with enzymatic extraction led to the reduction of inhibitory effects as well as to the simultaneous production of fatty esters which are compounds with several commercial applications. © 2001 Society of Chemical Industry