Production of kojic acid by membrane-surface liquid culture of Aspergillus oryzae NRRL484

Abstract

Membrane-surface liquid culture (MSLC) was applied to the production of kojic acid using Aspergillus oryzae NRRL484. The characteristics of kojic acid fermentation by MSLC were compared particularly with those by shaking culture. The maximum concentration of kojic acid produced and the production rate of kojic acid by the MSLC were usually higher than those by the shaking culture. In the shaking culture, the kojic acid production was the highest with 0.05–0.25% yeast extract and the maximum concentration was around 20 mg/ml. In the MSLC, the highest kojic acid concentration of about 30 mg/ml was obtained with 0.25–0.5% yeast extract. By addition of powdered glucose at a final concentration of 10%, 2–3 times at appropriate intervals during the batch MSLC, the concentration of kojic acid increased to over 100 mg/ml and kojic acid crystals formed in the medium. Repeated fed-batch production of kojic acid by MSLC was quite successful. The concentration of kojic acid produced in each batch was maintained at 75 mg/ml or more with a yield of around 50% for 10 batches and 75 d when the medium contained 0.25% yeast extract. The kojic acid productivity by the repeated fed-batch MSLC was 14.2 g/ l/d, about 6 times higher than that by the shaking culture with the medium containing 0.25% yeast extract. After the 11th batch, the production rate decreased, probably due to an increased amount of cells formed on the membrane.