Abstract: A process for producing citric acid/citrate for use in producing citric acid, comprising the steps of continuously feeding to a fermenter containing a yeast capable of transforming glucose to citric acid by fermentation, in the presence of a nutrient medium and oxygen, sugar, especially glucose as a C source and at least one ammoniun compound as an N source fermenting the sugar to citric acid in said fermenter at a temperature, a pH and with a residence time sufficient to transform at least a major part of the sugar continuously fed to said fermenter to citric acid continuously withdrawing fermentation product from said fermenter recovering citric acid/citrate from said fermentation product controlling a C/N ratio fed to said fermenter to correspond to a molar ratio of glucose to ammonium compounds of 12 to 22 during fermentation of the glucose to citrate.

Abstract: Strains of Aureobasidium pullulans (de bary) Arnaud can be used for the commercial production of gluconic acid by fermentation in aqueous liquid containing sugar, which in continuous culture from glucose form greater than or equal to 90% and greater than or equal to 90% molar selectivity. The process is conducted with an Fe and Mn optimized medium with a nitrogen-independent (N-independent) ion concentration. The iron (Fe) concentration with 3 g/l NH.sub.4 Cl is greater than or equal to 0.5 mM, and the manganese (Mn) concentration with 3 g/l NH.sub.4 Cl is greater than or equal to about 0.5 mM manganese (Mn). The pH is regulated between about 4.5 and about 8, in particular at 6.5-7, and the temperature between 24 and 32.degree. C., in particular at 29-30.degree. C. Particularly successful strains are Aureobasidium pullulans (de bary) Arnaud with the registration numbers DSM 7085, DSM 7086, DSM 7087, and DSM 7088.