Improvement of alcoholic fermentations by simultaneous extraction and enzymatic esterification of ethanol

Abstract

An extractive biocatalysis process consisting of a biphasic aqueous–organic system was studied for the enzymatic esterification of ethanol. Oleic acid was used simultaneously as organic extractant and substrate for the esterification reaction which was catalysed by a free and immobilized lipase from Rhizomucor miehei. The immobilization method used was the adsorption in a polyamide support—Accurel EP 700 [A.C. Oliveira, M.F. Rosa, J.M.S. Cabral, M.R. Aires-Barros, Bioprocess Eng. 16 (6) (1997) 349–353.]. Some relevant parameters for the lipase catalytic activity such as ethanol concentration, oleic acid concentration and pH were studied using a 2 (3) factorial design expanded further to a composite design (CCD) [G.E.P. Box, W.G. Hunter, J.S. Hunter, Statistics for Experiments, Wiley, New York, 1985; T.B. Barker, Quality by Experimental Design, Marcel Dekker, New York, 1985]. The response surface methodology was applied to the results. This biochemical process could be applied to the extraction of ethanol from fermentation broths of high glucose concentration [A.C. Oliveira, M.F. Rosa, J.M.S. Cabral, M.R. Aires-Barros, Bioprocess Eng. 16 (6) (1997) 349–353]. In this work, the performance of extractive fermentations of 300 g/l of glucose using a flocculent Saccharomyces cerevisiae saké strain and a non-flocculent Saccharomyces cerevisiae strain were compared.