EXTRACTIVE FERMENTATION---LACTIC ACID AND ACETONE/BUTANOL PRODUCTION

A wide range of chemicals and pharmaceuticals can be produced by fermentation. In most cases, however, the accumulation of toxic products in the fermentation broth inhibits their further production. Product inhibition can be reduced by removing inhibitory metabolites from the broth as they are produced. Extractive fermentation, a method of in-situ product recovery, is applied to two fermentations in this work: lactic acid production by Lactobacillus detbreuckii and the production of acetone and butanol by Clostridium acetobutylicum.;Production of acetone and butanol by extractive fermentation is also investigated. Batch extractive fermentation results show that volumetric productivity is increased by extracting inhibitory products from the broth during fermentation. Fed-batch extractive fermentation is shown to further increase butanol productivity and allow the use of concentrated substrates. Results of a continuous extraction system employing a Karr reciprocating plate extraction column are also presented and discussed.;Extraction column design in extractive fermentation is complicated by the formation of products inside the column. Approximate analytical solutions are derived to predict outlet concentrations from a differential contactor with product formation in one of the phases. The validity and practical implications of the solutions are discussed.;An economic analysis of butanol production by conventional batch and extractive fermentation indicates that substantial savings can be obtained by the use of extractive fermentation.;After reviewing previous work on the in-situ recovery of fermentation products, the application of extractive fermentation to lactic acid production is discussed. Quaternary amines and secondary or tertiary amines pretreated with a strong mineral acid are shown to extract lactate from aqueous solution. The effect of pH, lactic acid concentration and amine salt form on lactate extraction capacity is discussed. Biocompatibility of a number of organic extractants with L. delbreuckii is also examined. The feasibility of producing lactic acid by extractive fermentation is discussed and several alternative purification processes are presented.