The effect of gas sparging in cross-flow microfiltration of 2,3-butanediol fermentation broth

Recovery of 2,3-butanediol from a fermentation broth entails the separation of cells and other suspended solids as the initial step for subsequent separation stages. The aim of this work was to study the cross-flow filtration of broth in the fermentation of 2,3-butanediol from blackstrap molasses by Klebsiella oxytoca (NRRLB-199). A plate type laboratory scale cross-flow microfiltration unit with a 0.2-μm cellulose acetate membrane was employed for this purpose. Preliminary results showed that the permeate flux would decline rapidly due to fouling caused by the natural impurities of blackstrap molasses, and modifications of the conventional cross-flow filtration would be essential to achieve a filtration rate appropriate for practical purposes. In this work, the permeate flux was enhanced by air sparging, which scoured the membrane surface of colloidal deposits and allowed a practical filtration rate to be maintained. The average permeate flux increased by 39 % and 54 % for an air sparging rate of 0.5 L/min and 1.0 L/min respectively, in the case of an initial biomass concentration of 4.66 g/L. For an initial biomass concentration of 14.2 g/L, the flux increased by 105 % and 146 % for the gas rate of 0.5 and 1.0 L/min, respectively. It may be concluded that gas sparging is beneficial in cross-flow filtration of thick suspensions like a fermentation broth. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.