EFFECT OF OXYGEN AND NUTRIENT LIMITATION ON AJMALICINE PRODUCTION ANDRELATED ENZYME-ACTIVITIES IN HIGH-DENSITY CULTURES OF CATHARANTHUS-ROSEUS

Oxygen and nutrient limitation was investigated in order to identify t he origin of a lower specific ajmalicine production in Catharanthus ro seus cultures at high cell densities in an induction medium. The effec t of oxygen limitation was explored by comparing two identically aerat ed and agitated high cell density bioreactor cultures with dissolved o xygen (DO) concentrations of 15% and 85% of air saturation, with respe ct to alkaloid formation and related enzyme activities. Oxygen had an evident effect on ajmalicine production: in the high DO culture produc tion was more than 5 times higher than in the low DO culture. The diff erences in ajmalicine production between high and low DO could not be explained by the enzyme activity profiles. Moreover, the productivity in the high density culture could not be restored to the level of a lo w density culture (at a high DO) by increasing the DO alone. The effec t of nutrient limitation was studied with response surface methodology in shake flask cultures. Nutrient limitation could not be demonstrate d to be responsible for the productivity loss. Alkaloid and enzyme mea surements in the shake flask cultures supported previous findings that the tryptamine pathway may regulate alkaloid production, provided tha t the terpenoid pathway is sufficiently active. (C) 1994 John Wiley an d Sons, Inc.