Extractive fermenation is a very attractive process since in situ product removal could relieve inhibition problems. In order to study the potential of this technique, the reactive extraction of lactic acid was studied using several diluents and tertiary amine (Alamine 336) as a extractant.
Effects of several factors were evaluated on the membrane-based solvent extraction of lactic acid from fermentation broth. Those factors were the concentration of source solution, temperature, pH, stirring speed and the type of organic solvent.
In order to obtain the distribution data of lactic acid between aqueous and organic phases equilibrium studies were performed by varying the ratio of extractant and diluents in organic phase. Highest value of distribution coefficient was 3.5 when Alamine 336 and oleyl alcohol as a organic solvent mixture.
As the temperature increased from 25℃ to 42℃, the distribution coefficient increased by 8%. pH was the most important factor for the membrane-based solvent extraction of lactic acid. The distribution coefficient was bigger(2.7) than unity in pH 4.5, but smaller(0.9) than unity in pH 5.5. Stirring speed also was an important factor for achieving high performance in membrane-based solvent extraction.
In order to test the effectiveness of in situ recovery of lactic acid from fermentation broth, two cases of batch culture were carried out. : pH control only and pH control with membrane-based solvent extraction. When pH control with membrane-based solvent extraction is carried out, the productivity increased to 2.1 g/L/hr at pH 4.5. It is a higher productivity compared to that of a conventional batch fermentation(0.313 g/L/hr).
It is suggested that a membrane-based solvent extraction is a method for lactic acid production. However, economic feasibility study along with detailed parametric sensitivity should be demanded.
