Recovery of lactic acid from aqueous model solutions and fermentation broths

Abstract

The aim of the investigations was to recover lactic acid from fermentation broths in the presence of citric acid and acetic acid. For this purpose the reactive extraction of lactic acid was investigated from model media and fermentation broths with various carrier/modifier/solvent combinations. Experiments were performed using a secondary amine (Hoe F 2562), a tertiary amine (Hostarex A 327) as well as a phosphine oxide as carriers and butylacetate and kerosene as solvents. The effects of the type and concentration of the carrier and modifier and the temperature on the equilibrium distribution were evaluated. Relationships for the equilibrium distribution were developed and the calculated data were compared with the measured data. In the case of non-polar kerosene solvent, good agreement was found between the calculated and measured values. With the polar solvent, butylacetate, the physical extraction also had to be taken into account. By means of the developed relationships the adduct formation constants were determined for the extraction systems investigated. In order to investigate the selectivity of the carriers, tests were also performed to separate lactic acid from acetic and citric acid in model media and in fermentation broths. The separation of the acids is only possible in a multistage process. In situ extraction of lactic acid was not possible because of the toxicity of the carriers and modifiers.