Effect of the medium pH on the release of secondary metabolites from roots ofDatura stramonium, Catharanthus roseus, andTagetes patulacultured in vitro

The release of alkaloids from root culturesDatura stramoniumandCatharanthus roseusand thiophenes from root cultures ofTagetes patulawas 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 in each type of culture. Increases ranged from 4- to 20-fold, which in some cases accounted for 75% of the total secondary metabolite pool produced per flask. When the release of individual metabolites was measured, even larger increases, were observed (nearly 400-fold for ajmalicine). Increased release of alkaloids fromC. roseusroots were also observed 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 treatment as a stategy to improve the recovery of secondary metabolites from producing cultures is discussed.