Ethanol production by extractive fermentation

Abstract

The ideal method to produce a terminal metabolite inhibitor of cell growth and production is to remove and recover it from the fermenting broth as it formed. Extractive fermentation is achieved in the case of ethanol production by coupling both fermentation and liquid‐liquid extraction, The solvent of extraction is 1‐dodecanol (or a mixture 1‐dedecanol, 1‐tetradecanol); study of the inhibitory effect of primary aliphatic alcohols of different chain lengths shows that no growth is observed in the presence of alcohols which have between 2 and 12 carbons. This effect is suppressed when the carbon number is 12 or higher. A new reactor has been used–1 pulsed packed column. Pulsation is performed pneumatically. Porous material used as a package adsorbs the cells. The fermentation broth is pulsed in order to (1) increase the interfacial area between the aqueous phase and the dodecanol, (2) decrease gas holdup. Alcoholic fermentation, performed at 35°C on glucose syrup, permits the total utilization of glucose solution of 409 g/L with a yeast which cannot–in classical process– completely use solutions with 200 g/L of glucose. The feasibility of a new method of fermentation coupling both liquid‐liquid extraction and fermentation is demonstrated. Extension of this method is possible to any microbial production inhibited by its metabolite excretion.