Regulatory aspects of carbohydrate metabolism in relation to citric acid accumulation by aspergillus niger

Fermentative production by the fungus Aspergillus niger is the world's exclusive source of citric acid to be used for the food, pharmaceutical and detergents' industry. The extraordinary high yields and the delicate nutrient requirements of this process have attracted numerous investigations on its mechanism. This review highlights recent results on the regulation of its biosynthesis, emphazising especially (a) the role of pH, (b) the role of type and concentration of the carbon source, and (c) the role of anaplerotic carbon dioxide fixation in the accumulation of citric acid.