Factors Affecting Precipitation of Calcium Lactate from Fermentation Broths and from Aqueous Solution

Abstract

Lactic acid is one of the most important organic acids which is being extensively used around the globe in a range of industrial and biotechnological applications. Lactic acid can be produced either by fermentation or by chemical synthesis but the biotechnological fermentation process has several advantages compared to the other one. However fermentation broth contains a number of impurities which must be removed from the broth in order to achieve more pure lactic acid. Efficiency of recovery is crucial to the economy of the whole process as well since the costs of separation and recovery are responsible for more than half of the entire cost of production. In the traditional procedure, the heated and filtered fermentation broth is concentrated to allow crystallization or precipitation of calcium lactate, followed by addition of sulphuric acid to remove the calcium in form of calcium sulphate. The disadvantage of this procedure is the relatively high solubility of calcium lactate which causes product loss in the crystallization step. Therefore we investigated the effects of four operating parameters of the crystallization/precipitation process from two different fermentation broths and from an aqueous solution. Thus we applied three central composite statistical designs, in which the examined parameters were the temperature of the solution, the duration of the process, the effect of ethanol addition to the solution as well as the effect of multi-cycle precipitation after separation of the precipitated calcium lactate. According to the results, more than 50 percent calcium lactate precipitation increase can be obtained from fermentation broth by adding sufficient amount of ethanol and adjusting the proper temperature of the process.