Immobilized yeast cells （Candida lipolytica MX9-11 R3） were prepared by entrapping the whole cells in calcium alginate gel. The effects of minor elements on citric acid production were studied using the immobilized yeast cells in a fluidized-bed batch reactor.
One could more of less prevent the cell growth using glucose as the sole nutrient in the medium and thus removing other nutrients from the recipe for complex medium necessary for cell mass doubling.
When ferrous sulfate was added into glucose solution, the yield of citric acid was decreased whereas increasing the initial concentration of ammonium sulfate in the glucose solution resulted in the enhancement of the citric acid yield.
The optimal concentrations of zinc sulfate and cupric sulfate for citric acid production were found to be 5 mg/l, 0.05 mg/l respectively. Addition of either manganese sulfate or calcium chloride into the glucose solution had no appreciable effect on the citric acid production.