ALKANOL REMOVAL FROM THE APOLAR PHASE OF A 2-LIQUID PHASE BIOCONVERSION SYSTEM - PART 2 - EFFECT OF FERMENTATION MEDIUM ON BATCH DISTILLATION

In two-liquid phase fermentations organic substrates and/or products a re dissolved in an apolar phase while microorganisms are suspended in an aqueous medium. The effect of aqueous phase contaminants in the apo lar phase on the separation of products from the apolar phase by batch distillation is described in this paper. Various amounts of polar pha se, emulsified apolar phase and microorganisms normally present in the two-liquid fermentation medium were added to the organic phase. The r ecovery performance of a distillation unit in separating I-octanol fro m such contaminated apolar phases was determined. Further, the bulk pr operties of the emulsified apolar phase, such as its composition, the nature and the stability of the emulsion were analysed. It was found t hat the distillation performance is very sensitive to the presence of fermentation media in the organic phase. The energy cost per kg produc t recovered was almost doubled for only small additions of fermentatio n impurities. The emulsified apolar phase was shown to be kinetically, but not thermally, stable. Based on these results a suitable apolar p hase separation process before distillation can be developed, taking i nto account energy costs for phase separation and subsequent distillat ion, to optimize the overall downstream product purification process. (C) 1998 SCI.