GLUCOSE-STAT, A GLUCOSE-CONTROLLED CONTINUOUS CULTURE

A predictive and feedback proportional control algorithm, developed for fed-batch fermentations and described in a companion paper (G. L. Kleman, J. J. Chalmers, G. W. Luli, and W. R. Strohl, Appl. Environ. Microbiol. 57:910-917, 1991), was used in this work to control a continuous culture on the basis of the soluble-glucose concentration (called the glucose-stat). This glucose-controlled continuous-culture system was found to reach and maintain steady state for 11 to 24 residence times when four different background glucose concentrations (0.27, 0.50, 0.7, and 1.5 g/liter) were used. The predictive-plus-feedback control system yielded very tight control of the continuous nutristat cultures; glucose concentrations were maintained at the set points with less than 0.003 standard error. Acetate production by Escherichia coli B in glucose-stats was found not to be correlated with the level of steady-state soluble-glucose concentration.