The effect of temperature on the trace element requirements for citric acid production by aspergillus niger

The effect of temperature of fermentation on the production of citric acid, and on the trace element requirements for the maximum production of citric acid by Aspergillus niger 72-4 were studied. Yield and efficiency of production of citric acid were progressively greater from 33° to 23°C. However, in order to obtain maximum yields of citric acid at temperatures lower than 30°C. it was necessary to increase the levels of the trace minerals, zinc, iron, copper and manganese, above those found to be optimal at 30° C. The trace mineral requirement for maximum acid production at 25°C. was twice as great as that at 30°C. which in turn was twice as great as that at 33°C. in addition, fermentation at the lower temperature was much less sensitive to excesses of the various trace element than at a higher temperature. A mineral balance which is affected by temperature of fermentation is involved in the nutrition of A. niger for optimal citric acid production. Fermentation time is longer at 23°C. than at 30°C. However, the acid yield per unit of carbohydrate used is higher at the lower temperature. Trace elements other than zinc, iron, copper and manganese are probably essential for maximum acid production, preliminary evidence was obtained which indicated that cobalt and molybdenum were active in this respect.Land and Food Systems, Faculty ofGraduat