PURIFICATION OF L(+)-LACTIC ACID

The Aim, the Signaficance, and the Expected Outcomes of the Project:
    Having two optically active forms as D(-) and L(+), lactic acid has long been used in the food industry as acidulant, flavour enhancer and antimicrobial agent. It has also been utilized in leather, textile, pharmaceutical and cosmetic industries for years. Besides, L(+)-lactic acid constitutes the raw material for the production of poly-L-lactic acid which is biocompatible and body absorbable.

    When lactic acid is produced by microbial processes, it should be recovered from the fermentation media efficiently and economically. It should also be obtained at high purity especially for biomaterial applications. The cost of lactic acid is mainly due to the downstream processing costs rather than its production costs. Among the various downstream processing operations, ion exchange chromatography is highly selective and yields a low cost product recovery within a short time.

    In this project, Lactobacillus casei will be utilized for the production of L(+)-lactic acid from whey by fermentation under suitable operating conditions. In the subsequent steps, lactic acid will be separated from the other impurities which are present in fermentation broth and will then be purified. In this frame, the optimum operating conditions should be determined. For this purpose, first, the interaction of model lactic acid solutions with anion exchangers and the adsorption/desorption behaviours will be investigated. The capacity of ion-exchangers, the adsorption isotherms and adsoption/desorption kinetics will be obtained and the rate of adsorption will be determined. Then, the purification of actual fermentation broths will be carried out by applying the experimental results and the theoretical model parameters. By this way, the most suitable and efficient method for the purification of L(+)-lactic acid will be determined.

    In the light of the results of this project, the possibility of the purification of L(+)-lactic acid with an inexpensive method, the end product purity and the economic recovery and applicability in industrial usage will also be investigated.

    Although lactic acid fermentation have been studied for years, the research on L(+)-lactic acid fermentation and purification has started in recent years, so, there is lack of information in the literature on this subject. Therefore, an additional aim of the project is to obtain new data on the adsorption/desorption behaviours of organic acids and the understanding of the mass transfer mechanisms.