Development of a fermentation process for production of calcium-l-lactate

This study is an effort to develop an efficient process for low-cost production of calcium-l-lactate (CaL2). CaL2 showed higher inhibitory effect on lactate production than ammonium-l-lactate (NH4) at lactate concentration lower than 100 g/L, but it showed lower inhibitory effect at higher lactate concentration. The strain Lactobacillus rhamnosus (NBRC 3863) was resistant to glucose inhibition and final CaL2 concentration increased with initial glucose concentration increasing up to 190 g/L. High-concentration CaL2 induced, however, flocculation of fermentation broth, causing incomplete fermentation. It was confirmed that stirring speed markedly influenced flocculation, an increase of the stirring speed leading to an earlier flocculation. Formation of colloidal CaL2 during fermentation was considered to be the cause of flocculation in this study. Addition of YE raised fermentation efficiency and made complete fermentation feasible. In the fermentation with 25 g/L YE, glucose was completely consumed and final CaL2 concentration of 220 g/L was obtained, when flocculation did not yet occur. In this study, CaL2 crystals and activated carbon powder were added as nucleation sites to get earlier crystallization of colloids and to decrease the inhibitory effect of CaL2, and so to increase productivity. Of the two nucleation sites, activated carbon powder showed higher performance in CaL2 production. Finally, the feasibility of crystallization-based recovery without concentration step was discussed.