Studies on citric acid fermentation using $\underline{A. niger}$ medium were carried out in submerged cultures in both shaking flasks and bubble column reactor.
The effect of sugar source (sucrose,glucose,fructose) was examined, sucrose-which was the best carbon source-concentration was 60 g/L for the optimum condition for maximum yield of citric acid. Repeated fed batch experiment was carried out for high production of citric acid. (78g/L for sucrose addition,83g/L for sucrose and ammonium nitrate addition)
The technique of cell immobilization using biomass support particles-polyurethane foam in this experiment-applied to $\underline{A. niger}$ For investigating the feasibility of polyurethane foam as support particle in bubble column reactor the several size and concentration of polyurethane foam matrices was examined and culture was carried out for several nitrogen concentrations.
As a result it was found that the ammonium nitrate concentration for good operation and citric acid production was 0.5 g/L, in this condition the oxygen concentration was higher than free cell culture.
