Mass cultivation of Medicago sativa growing on lactose: Kinetic aspects

Summary Batch cultures of Medicago sativa cells have been carried out in the dark under aerobic conditions using lactose as the sole carbon source. The stoichiometric analysis has been correlated with both the oxygen demand and the cell productivity in an oxygen-limited cultivation. The minimum oxygen transfer has been estimated to be 12.5 h^–1, i.e., 0.3 v.v.m; this initial aeration rate led to cell necrosis. Starting with a low oxygen transfer coefficient k_L·a and increasing the air flow rate during the course of fermentation gave an exponential growth phase. The maximum specific growth rate was 0.012 h^–1 and the growth yield was 0.43 g.d.w./g. of lactose. On the basis of the mass-balance relation the maintenance coefficient and the maximum growth yield have been calculated.