Studies on osmolarity, conductivity and mass transfer for selection of a bioreactor for Tagetes patula L. hairy roots

Growth of hairy roots of Tagetes patula L. was estimated by correlating bio mass growth with conductivity and osmolarity changes in the medium. An inve rse relationship was observed between biomass and osmolarity as well as con ductivity. Osmolarity was demonstrated to be the more accurate method for t he estimation of biomass. Maximum biomass was observed on the 15th day of c ulture period at 81.25 g (fresh wt) litre (-1) or 6.9 g (dry wt) litre (-1) . A maximum thiophene content of 2.5 mg litre (-1) was observed on the 13th day. Correlations were developed without taking the initial values of biom ass, conductivity and osmolarity. Systematic experimentation was carried ou t in order to determine the relative significance of gas-liquid and solid-l iquid mass transfer, which will form the basis for the selection of a suita ble bioreactor for this system. At any given shaker speed the biomass growt h (g litre (-1)) decreased with increasing volume of the culture medium. Si milarly at any given volume of the culture medium biomass growth increased with an increase in shaker speed. The former indicates the importance of ga s-liquid mass transfer, while the latter emphasizes the importance of solid -liquid mass transfer. The thiophene content also showed a similar trend wi th the variation of rotation speed and media volume. These results led to t he inference that T. patula hairy roots are relatively non-shear sensitive. The observations of the present study provide guidelines for the selection of a suitable bioreactor for the cultivation of T. patula hairy root cultu res. (C) 2001 Elsevier Science Ltd. All rights reserved.