The purpose of this study is to improve the productivity of ornithine by Brevibacterium ketoglutamicum BK1047. First, the composition of culture media was optimized in flask culture. Yeast extract as an arginine source and ammonium sulfate as an inorganic nitrogen source had significant effects on ornithine production and cell growth. Inhibition and repression of ornithine production from excessive addition of arginine was observed. Time patterns of cell growth and ornithine production and phenomena which occurred as each component was depleted were investigated in batch culture in a fermentor. The optimum concentration of yeast extract and ammonium sulfate were obtained. Effects of dissolved oxygen tension (DOT) were observed by DOT-stat experiments. The production of ornithine was influeced by DOT. At a high DOT a greater amount of ornithine was produced. In DOT-stat experiemnts, the behaviors of redox potential and agitation speed showed a very interesting feature. They were closely related to the cell growth. The slope of the redox potential changed with cell growth rate. Therefore it was concluded that redox potential could be used as an indicator for metabolic state of the culture. The feasibility of estimating specific growth rate from carbondioxide evolution rate (CER) and agitiation speed (RPM) was tested. The estimation results in both cases were in a good agreement with the actual data. This means that both CER and RPM can be used to monitor the metabolic state of the culture and also to develop a control policy to maximize the ornithine production.
