Production of L‐lactic acid by Lactobacillus delbrueckii in chemostat culture using an ion exchange resins system

L ‐Lactic acid production from beet molasses by Lactobacillus delbrueckii CECT 286 in a continuous fermenter‐ion exchange resins system has been investigated and compared with that observed in a conventional chemostat. The principle of this method is to remove the lactate during the course of fermentation as it is formed by adsorption to an anion exchange resin (Amberlite IRA‐420) in the carbonate form and to overcome its inhibitory effects on lactic acid bacteria by maintaining low lactate concentrations in the medium. Ammonium lactate was formed by percolating ammonium carbonate solution through this resin and it was converted to lactic acid by treatment with a cation exchange resin (Amberlite IR‐120) in hydrogen form. Compared with a conventional chemostat, this fermentation–ion exchange resins system enhanced the fermentation, controlled the pH, and showed the remarkable effect of increasing the yields of lactic acid from sucrose and biomass from sucrose due to the complete utilization of sucrose. © 1999 Society of Chemical Industry