ALKANOL REMOVAL FROM THE APOLAR PHASE OF A 2-LIQUID PHASE BIOCONVERSION SYSTEM - PART 1 - COMPARISON OF A LESS VOLATILE AND A MORE VOLATILEIN-SITU EXTRACTION SOLVENT FOR THE SEPARATION OF 1-OCTANOL BY DISTILLATION

Biocatalytic systems can be used for the regio-and stereospecific synt hesis of oxidized alkanes and aromatic compounds, such as aliphatic an d aromatic alcohols, aldehydes and epoxides. These reactions are typic ally carried out in two-liquid phase media. The biocatalyst is usually a natural microorganism, often a Pseudomonas, or a genetically altere d host, a Pseudomonas or E. coli recombinant typically, which grows in the aqueous phase, while the substrate and product are present in an organic bulk phase. Oxidation products formed in these systems must be purified after separation of the two liquid phases. We have evaluated the performance of distillation for the separation of the product 1-o ctanol by examining a more volatile (octane) and a less volatile (hexa decene) in-situ extraction system. The separation performance of the t wo systems has been compared based on recovery efficiency, energy cost and number of required process units. Results showed that a less vola tile extractant compared favorably in terms of number of product separ ation unit steps, decreased operating and energy cost to the use of a more volatile extraction solvent. In addition, a major disadvantage of the more volatile in-situ extraction process was the coloring of the bottom product of the first distillation step, in which the product is contained in this case. Such modifications can be implemented into an upstream and downstream process of bioconversions to improve the over all system and to reduce downstream processing cost. (C) 1998 SCI.