Chapter IX The Measurement of Oxygen Absorption and Carbon Dioxide Evolution in Stirred Deep Cultures

Abstract

Publisher Summary The measurement of oxygen (O 2 ) consumption and carbon dioxide (CO 2 ) evolution as features of microbial metabolism and their relationship, along with dissolved O 2 tension, creation of microbial substance, substrate utilization or product formation, is of importance in understanding and controlling microbial processes. The CO 2 and O 2 concentration in the effluent air stream are a measure of the metabolic rate of the process, and therefore continuous analysis is of great value as a supervisory tool. As well as analyzing the effluent gas from aerobes for CO 2 and O 2 and that from anaerobes for CO 2 , it is also necessary to know the inlet air rate in aerobic cultures and the effluent gas rate in aerobic and in anaerobic cultures. Effluent gas rate in aerobic cultures can be calculated if the inlet air rate and the analysis of the effluent gas are known. The Orsat apparatus is described (along with the Haldane apparatus) in a British Standard (British Standards Institution, 1952) that deals with the analysis of flue gases. It is cited as “the best known apparatus . . . for the determination of CO 2 , O 2, and CO where a high degree of accuracy is not required.” There are two methods for the continuous analysis of O 2 in gases, both of which depend on the paramagnetic properties of O 2 gas. In fermentation work, the magnetic wind instrument appears to be less in favor than the Pauling type. In the Pauling type, a dumb-bell formed by two hollow glass spheres is suspended on a taut fiber in a magnetic field.