Improvement of the Lactic Acid Extraction. Extraction From Aqueous Solutions and Simulated Fermentation Broth by Means of Mixed Extractant and TOA, Partially Loaded with HCl

D. Yankov, J. Molinier, G. Kyuchoukov, J. Albet and G. Malmary

Abstract
Lactic acid is an important chemical product with wide use in many industrial fields. About a half of world production of lactic acid is made by fermentation of different sugars by means of Lactobacillus sp. strains. Two methods for overcoming the problems, arising from the difference in pH optima for extraction and fermentation in the extractive lactic acid fermentation, are proposed. The first method is based on the use of a mixed extractant composed by tri-n-octylamine (TOA) and Aliquat 336 (methyltrioctylammomium chloride), dissolved in decanol and dodecane. The use of mixed extractant leads to increase in extraction performance in comparison with individual extractants. The extraction efficiency depends on initial acid concentration, pH and Aliquat/TOA ratio as well. While at 5 gl–1 lactic acid the distribution coefficient increase with increasing of Aliquat concentration, for 10 and 25 gl–1 lactic acid the value of distribution coefficient passes through maximum. With increase of acid concentration the position of the maximum shifts to higher TOA concentration. The second method includes the use of tri-n-octylamine (TOA) partially converted to amine hydrochloride. This approach leads to increase in the extraction performance in comparison to the extraction with TOA at high pH values. The extraction efficiency depends on initial lactic acid concentration, pH value, and degree of loading with HCl.

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Keywords
lactic acid, extraction, mixed extractant, modified extractant, trioctylamine, Aliquat 336