The effect of inoculum density and conditioned medium on the production ofajmalicine and catharanthine from immobilized Catharanthus roseus cells

The effect of the cell-inoculum size and the addition of conditioned medium on ajmalicine and catharanthine production were studied using immobilized Catharanthus roseus cells. Higher specific-uptake rates of ammonium, nitrat e, and sugars were observed in the low-inoculum-density cultures (50 g FW/L ) compared to the high-inoculum-density cultures (100 g FW/L). Alkaloid pro duction was not correlated with the exhaustion of a particular nutrient fro m the medium. The high-inoculum-density cultures produced higher ajmalicine concentrations throughout the experiment. Catharanthine production was sim ilar between the two inoculum-density cultures. The addition of conditioned medium to MS-production medium dramatically imp roved the production of ajmalicine and catharanthine. The addition of condi tioned medium enhanced ajmalicine production from immobilized Catharanthus roseus cultures on day 15 by at least two- to fourfold compared to media wi thout the conditioning factors. Catharanthine production was increased by n early fivefold in cultures with conditioned medium compared to those withou t conditioned medium. The enhancing effects of conditioned medium on alkalo id production were attributed to an unidentified factor produced and secret ed by suspension cultures of C. roseus. The presence of conditioned medium also decreased the sucrose hydrolysis rate. The ajmalicine concentration in these immobilized cell cultures was found t o be a function of the fresh-weight concentration, irrespective of the inoc ulum density or the culture medium. The medium choice and the inoculum dens ity determined how rapidly fresh weight was accumulated and thus, how quick ly ajmalicine was produced. Ajmalicine production correlated positively wit h fresh-weight concentration, but catharanthine production was not correlat ed with fresh-weight concentration. (C) 2000 John Wiley & Sons, Inc.