Abstract
The use of liquidβliquid extraction for the recovery of biological products from fermentation media by direct extraction may be significantly influenced by the presence of impurities. This can offset the process advantages of using direct whole broth extraction which, if feasible, can reduce the number of stages needed for the required separation. The impurities may slow down mass transfer rate and may also affect the thermodynamic distribution of the required solute into the extracting solvent. In some cases the addition of reagents can be beneficial to the extraction. Here an experimental study is described in which the partitioning of citric acid into nβbutanol in the presence of a range of impurities has been measured. A range of impurities and additives were studied in an attempt to quantify and prioritise those compounds which affect the partition in practice. These comprised a range of proteins, electrolytes, a surfactant and other organic acids. The additives considered included: trypsin, bovine serum albumin, sodium lauryl sulphate, glucose, sucrose, lactic acid, magnesium sulphate and, sodium chloride. The modification of citric acid partitioning into nβbutanol from whole broth, filtered broth and suspensions of reconstituted biomass were also compared. The presence of the proteins and sodium had a detrimental effect on partition. The effect of magnesium sulphate was highly concentration dependent.