THE ROLE OF GLUCOSE IN AJMALICINE PRODUCTION BY CATHARANTHUS-ROSEUS CELL-CULTURES

The role of glucose in ajmalicine production by Catharanthus roseus wa s investigated in the second stage of a two-stage batch process. Activ ities of tryptophan decarboxylase (TDC) and anthranilate synthase (AS) , two enzymes in the pathway leading to ajmalicine, were higher after induction with 40 g/L glucose than after induction with 60 or 80 g/L g lucose. Experiments with different media containing mixtures of glucos e and the nonpermeating osmotic agent xylose, and using an already ind uced culture as inoculum, revealed that a minimum amount of glucose is required to support ajmalicine production after enzyme induction. Thi s requirement was not an osmotic effect. The relation between the gluc ose concentration and the specific ajmalicine production rate, q(P), w as investigated in seven (fed-)batch cultures with constant glucose co ncentrations: 23, 29, 35, 53, 57, 75, and 98 g/L. In the cultures with a low glucose concentration (23, 29, and 35 g/L) the q(P) was 2.7-tim es higher than the cultures with 53 and 57 g/L, and almost six times h igher than the cultures with a high glucose concentration (75 and 98 g /L). A glucose perturbation experiment (from 53 to 32 g/L) demonstrate d that the ajmalicine production rate was adjusted without much delay. A kinetic equation is proposed for the relationship between the gluco se concentration and q(P). Differences in enzyme induction and ajmalic ine production at different glucose levels could not be explained by t he intracellular concentrations of glucose, fructose, sucrose, or star ch. (C) 1995 John Wiley and Sons, Inc.