Verfahren zur kontinuierlichen Fermentierung

The invention relates to a process for continuous fermentation, in particular a process for the continuous fermentation of acetic acid. Fermentation is performed in two fermentation units, whereby the first fermenter is operated at optimum efficiency by controlling the substrate feed by a measurement and control system and the subtraction concentration and thus the product concentration is kept constant at stationary conditions and constant volumetric rate of flow. A residual fermentation is fed through the second fermenter by transferring the contents of the first fermenter to the second fermenter, whereby the biomass transfer from the first fermenter to the second fermenter is determined by the bleed rate and is adjusted by a measuring and control system in such a way that the biomass required for residual fermentation is available in the second fermenter. In both fermentation stages, a direct product discharge is performed via microfiltration and/or an ultrafiltration unit and the r esidue of the micro/ultrafiltration is returned to the fermenter, whereby, in the second fermentation stage, a partial flow is removed from the system as required. The product is concentrated and/or obtained from the permeate of the micro/ultrafiltration of the second fermenter using normal methods.