KINETIC AND STOICHIOMETRIC ANALYSIS OF HAIRY ROOTS IN A SEGMENTED BUBBLE-COLUMN REACTOR

Hairy roots of Atropa belladonna were cultured in a modified 2.5-L mul ticompartment bubble column for analysis of growth kinetics, stoichiom etry, and atropine production. Average biomass density reached 9.9 g L (-1) dry weight after 43 days of batch culture; local root densities i n some parts of the vessel were considerably higher, up to 17 g L(-1). Bulk mixing in the reactor was very poor: after 14 days of culture, t he time taken to reach 95% of the equilibrium value after a concentrat ion pulse in the vessel was 12 min. Growth and specific sugar uptake r ates declined continuously throughout the culture even though adequate sugar and nitrogen remained in the medium. The observed biomass yield from sugar was approximately constant at 0.35 g g(-1); yields from am monia and nitrate were 0.44 and 0.35 g mmol(-1), respectively. Specifi c atropine content in the roots varied from 4.1 mg g(-1) dry weight at the beginning of the culture to 1.4 mg g(-1) after 28 days; 35 mg or 14 mg L(-1) atropine was produced over the 43-day culture period. Biom ass composition was represented by the elemental formula CH1.63O0.80N0 .13, plus 9.8% (w/w) ash. A balanced stoichiometric equation was devel oped for hairy root growth; this indicated that 8.3% of carbon supplie d to the culture was excreted into the medium as byproducts.