A study was made on the in-situ recovery of the fermentation products glutamic acid and gluconic acid by selective adsorption and ion exchange. The addition of the ion exchanger to the ＇＇batch-fermentation＇＇ led in both cases to the inhibition of the fermentation process. By the circulation of the fermentation broth over ion exchange columns the contact time between the ion exchanger and the microorganism was decreased which led to the usual growth of the microorganism. In the case of the gluconic acid fermentation the selective ion exchange of the products caused an increase of the conversion rate and the selectivity of the process. For the decrease of the glutamic acid production the coadsorption of biotin was assumed.