Kinetics of kojic acid fermentation by Aspergillus flavus using different types and concentrations of carbon and nitrogen sources

摘要

Kinetics of kojic acid fermentation by Aspergillus flavus Link 44-1 using various sources of carbon [glucose, xylose, sucrose, starch, maltose, lactose or fructose] and nitrogen [NH_4Cl, (NH_4)_2S_2O_8, (NH_4)_2NO_3, yeast extract or peptone] were analyzed using models based on logistic and Luedeking-Piret equations. The highest kojic acid production (39.90 g l~(-1)) in submerged batch fermentation was obtained when 100 g l~(-1) glucose was used as a carbon source. Organic nitrogen sources such as peptone and yeast extract were favorable for kojic acid production as compared to inorganic nitrogen sources. Yeast extract at 5 g l~(-1) was optimal. The optimal carbon to nitrogen (C/N) ratio for kojic acid fermentation was 93.3. In a resuspended cell system, the rate of glucose conversion to kojic acid by cell-bound enzymes increased with increasing glucose concentration up to 70 g l~(-1), suggesting that the reaction followed the Michaelis-Menten enzyme kinetic model. The value of K_m and V_(max) for the reaction was 18.47 g l~(-1) glucose and 0.154 g l~(-1) h~(-1), respectively.