Improvement of intracellular beta-galactosidase production in fed-batch culture of Kluyveromyces fragilis

Four fed-batch control strategies were evaluated to improve the specific la ctase activity of Kluyveromyces fragilis. Control strategies tested include d DO-stat control, exponential feeding, exponential feeding with manual fee dback control and corrected feed-forward control. Each was implemented with standard sensors (i.e., temperature, dissolved oxygen and pH sensors) comm only installed in fermenters. The highest specific activity was obtained us ing the corrected feed-forward control strategy, a strategy incorporating a novel method for on-line estimation of specific growth rate. The control s trategy was able to operate effectively to a final cell density of 69 g dry wt l(-1) with a specific lactase activity of 2 U mg(-1) cell dry wt.