EFFECT OF THE MEDIUM PH ON THE RELEASE OF SECONDARY METABOLITES FROM ROOTS OF DATURA-STRAMONIUM, CATHARANTHUS-ROSEUS, AND TAGETES-PATULA CULTURED IN-VITRO

The release of alkaloids from root cultures Datura stramonium and Cath aranthus roseus, and thiophenes from root cultures of Tagetes patula w as found to increase when the pH of the culture media (ranging from 4. 8 to 7.0) was reduced to 3.5. The extent of the effect was different i n each type of culture. Increases ranged from 4- to 20-fold, which in some cases accounted for 75% of the total secondary metabolite pool pr oduced per flask. When the release of individual metabolites was measu red, even larger increases were observed (nearly 400-fold for ajmalici ne). Increased release of alkaloids from C. roseus roots were also obs erved in cultures growing in a 14-L fermentor, when the medium pH was reduced. Reduction of the pH of the media did not affect growth of the root cultures in subsequent subcultures. The importance of this treat ment as a stategy to improve the recovery of secondary metabolites fro m producing cultures is discussed.