title: Transient studies of nutrient uptake, growth, and indole alkaloid accumulation in heterotrophic cultures of hairy roots of Catharanthus roseus.
abstract: The kinetics of growth, the uptake of macronutrients, and the accumulation of indole alkaloids were investigated in long-term, heterotrophically cultured transgenic ("hairy") roots of Catharanthus roseus.Tabersonine, ajmalicine, and serpentine were monitored over a 70-day period. The doubling time [dry-weight (DW) basis] of C. roseus hairy roots in B5/2 nutrients supplemented with 3% sucrose was 3.6 days. NH(4)(+), NO(3),(-) and P(i) were depleted sequentially from culture medium by hairy roots, while sugars remained undepleted. The growth-limiting nutrient was inorganic nitrogen, NH(4)(+) and NO(3)(-), with exponential-phase overall biomass yields of 34.1 and 5.0 g DW/g nutrient, respectively. Extracellular pH decreased to 4.8 in early exponential phase of culture growth from the initially adjusted value of 5.7, increased subsequently to a maximum of 7.7 in late exponential phase of growth coincident with the maximum of fresh weight (FW)/DW ratio, before decreasing to 5.5-5.0. The organic acids, pyruvate, formate, lactate, and succinate were excreted by hairy roots starting in late phase of exponential growth, possibly resulting in the late-culture pH decrease. Tabersonine accumulation was distinctly growth associated with maximum specific and total yields of 1.15 mg/g DW and 5.6 mg/L, respectively, in late-exponential phase of growth. Serpentine accumulation was non growth associated with increasing specific and total levels in stationary growth phase: 1.3 mg/g DW and 10.5 mg/L, respectively. The accumulation of ajmalicine also appeared growth associated.
authors.affiliation: Department of Chemical Engineering, Institute of Biosciences and Bioengineering, Rice University, Houston, Texas 77005-1892, USA.
authors.forename: R
authors.initials: R
authors.lastname: Bhadra
authors.forename: J V
authors.initials: JV
authors.lastname: Shanks