Patent ID: 8772033

Claim:
A method of multiplying plant embryogenic tissue in a bioreactor comprising the steps of: (a) inoculating plant embryogenic tissue and multiplication medium into a bioreactor; (b) measuring a parameter that is a direct measure of, or correlated to, a concentration of the plant embryogenic tissue in the bioreactor; (c) determining a target value of the parameter; (d) taking the measurement obtained in step (b) and the target value determined in step (c) to calculate a flow rate of additional multiplication medium, wherein when the parameter is dry weight concentration, the flow rate of additional multiplication medium is calculated using the equation: f = - 100 Δ ⁢ ⁢ B target ⁢ x o ⁢ k eff Y x / s ⁢ exp ⁡ ( k eff ⁢ t ) wherein ΔB target is the difference between a Brix value of a target culture supernatant (B sp ) and a Brix value of fresh medium to be added (B m ); Y x/s is an amount of biomass produced divided by an amount of sugar consumed; biomass (x) is culture volume (V) multiplied by dry weight biomass concentration (X); x 0 is the initial biomass; k eff is effective growth rate; and t is time; wherein when the parameter is sugar concentration, Brix or electrical capacitance, the flow rate of additional multiplication medium is calculated using the equation: f=V o ·k f exp└ k f t┘ wherein V o is an initial volume of a bioreactor, k f is a flow rate factor, and t is time; wherein a proportional integral feedback controller is used to calculate the flow rate factor, and wherein the proportional integral feedback controller is a non-linear, discrete proportional integral controller; (e) delivering additional multiplication medium to the bioreactor based on the flow rate calculated in step (d); and (f) periodically repeating steps (b) to (e).