A novel concept of bioreactor. Specialized function two-stage continuous reactor, and its application to lactose conversion into lactic acid

From reactors performing a continuous production of an inhibitory metabolite like lactic acid, high product concentrations are obtained only at very low dilution rates. For such systems, volumetric productivity may be improved with the help of a novel two-stage reactor equipped with a separate feeding line in the second stage. By pumping a medium optimized for growth in the first stage and not controlling the pH of this reactor, an active seed culture (containing a small concentration of lactic acid) was prepared in continuous mode; this inoculum and a medium optimized for lactic acid production were fed in the second stage. Since 97% of the total amount of lactic acid was produced in the second stage, the system has been called 'specialized function two-stage reactor'; the volumetric productivity obtained from this novel configuration was close to batch one in similar conditions.