Release of Citric Acid into the Medium by Aluminum-Tolerant Carrot Cells

One physiological characteristic of an Al-tolerant cell line (TA-1) selected from a cultured carrot cell line (SO-1) was the release of more citric acid into the medium than the parental SO-1 line. Aluminum chloride was added to the media at a concentration, at which SO-1 as well as TA-1 could grow normally without inhibition. The amounts of citric acid and the soluble Al present in the medium were determined during the growth period. Much citric acid was released from TA-1 cells into the medium in the first half of the culture period. At the time of maximum growth, the amount of citric acid in the medium of TA-1 cells was twice as much as in the medium of SO-1 cells. The precipitates of Al compound(s), which were formed in the medium by the addition of AlCl3 as the Al source, became soluble as culture proceeded, depending on the amount of citric acid present in the medium.