The Oxygen Requirement of Growing Cultures of an Aerobacter Species Determined by means of the Continuous Culture Technique

Abstract

SUMMARY: A formula for calculating the oxygen demand of a growing culture is derived. The fate of substrate-glucose in cultures of Aerobacter cloacae was found to depend on the amount of available oxygen and the oxygen demand of the organisms. Anaerobically, cell synthesis and CO₂ production are at their minimum levels and most of the glucose-carbon is converted into ethanol, formic acid, 2:3-butanediol, acetoin and acetic acid. A small supply of oxygen suppresses the formation of ethanol and formic acid but still permits the production of butanediol and acetoin and increases the proportion of glucose-carbon converted to acetic acid, cells and CO₂. A larger supply of oxygen suppresses the formation of butanediol and acetoin and still further increases the yields of cells and CO₂. With an excess of oxygen available, provided the growth rate of the organism is not too near its maximum value, acetic acid production is suppressed and complete conversion of the glucose-carbon into cell and CO₂ occurs. At growth rates very close to the maximum a part of the glucose is converted into acetic acid even with an excess of available oxygen. The metabolism in a batch culture with excess oxygen resembles the metabolism with excess oxygen in a continuous cultures in which the organisms are growing at a rate close to the maximum. Means of recognizing and preventing an oxygen deficiency are discussed.