Start-up of chemostat: Application of fed-batch culture

A time-optimal strategy for start-up of a chemostat has been established by applying Miele's extremization method based on Green's theorem. The start-up time is always minimized by traveling along the uppermost boundary of the set of admissible domains on the (vx, μ) phase plane. The solutions are batch culture for monotone increasing growth kinetics and exponentially fed-batch culture followed by batch culture for substrate-inhibition kinetics. A time-suboptimal start-up strategy, exponentially fed-batch culture operated the same μ as that of chemostate, is proposed as more feasible than and physiologically preferable to the time-optimal strategies. The complete set of equations of operations necessary for performing each of the optimal and suboptimal start-ups is formulated. Numerical comparisons on the basis of continuous operation giving maximum productivities of cell-mass outputs show that differences in times required for start-up between optimal and suboptimal strategies are small.