SOLVENT SCREENING FOR PRODUCTION OF LACTIC-ACID BY EXTRACTIVE FERMENTATION

The extraction of lactic acid from aqueous solution by a number of ext ractants dissolved in different organic diluents was explored over a w ide range of pH values. Tri-n-octylmethylammonium chloride (TOMAC or Q Cl), dissolved in oleyl alcohol, butyl acetate, and a mixture of hexan e and oleyl alcohol, was found to be most appropriate in terms of high extraction capacity and simplicity of operation. Biocompatibility bet ween the extraction reagents and lactic-acid-producing microbes was al so examined. The results indicated that TOMAC was highly toxic, and bo th butyl acetate and hexane exhibited some detrimental effects. Howeve r, oleyl alcohol exhibited no toxicity and could, therefore, be consid ered the most suitable diluent. During extractions with TOMAC concentr ations no greater than 0.1 kmol.m(-3), implementation of a cleaning co lumn filled with oleyl alcohol seemed to effectively remove trace amou nts of TOMAC dissolved in the fermented broth; extractive fermentation of lactic acid was accomplished, despite a little decline in lactic a cid production relative to production obtained for a control experimen t. However, higher TOMAC concentrations are desired for better extract ion of accumulated lactic acid to reduce its own inhibitory effect. A cleaning column packed with the cation-exchange resin Amberlite IR-120 B was more effective. As a result, satisfactory extractive fermentatio n was achieved, thereby proving the feasibility of efficiently produci ng lactic acid by extractive fermentation, with TOMAC dissolved in ole yl alcohol as the optimum extraction system.