Growth and Antithraquinone Biosynthesis byGalium mollugoL. Cells in Batch and Chemostat Culture

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Abstract
The kinetics of growth, nutrient uptake, and anthraquinone biosynthesis by suspension cultures of Galium mollugo L. cells were examined in batch and continuous (chemostat) culture. In batch culture, although the initial growth rate was constant (minimum doubling time = 35 h) characteristic changes in cell composition were observed during the growth cycle particularly cell dry weight (between 3.9 and 9.2 g/109 cells), cell anthraquinone (22–80 mg/109 cells), and cell protein (0.7–1.6 g/109 cells). Using a chemostat steady state growth was established at two different specific growth rates with mean doubling times of 40 h and 25 h. Phosphate was established as the growth-limiting nutrient in chemostat culture at a concentration of 11 μg P ml−1. In steady state growth at a doubling time of 40 h the cell composition remained constant although this was different from any cells grown in batch culture. The cell anthraquinone level in steady state growth was between 7 and 30 times lower than in batch culture. This result raises the question of the relative importance of growth rate and the growth-limiting nutrient in determining accumulation of secondary products by cultured plant cells.