Oxygen‐absorption rate‐controlled feeding of substrate into aerobic microbial cultures

Abstract

SummaryA system of automatic control of substrate inflow into an aerated culture of microorganisms which depend on oxygen-absorption rate (OAR) has been devised and tested. As the control variable, dissolved oxygen concentration (DOC), which shows the equilibrium between OAR and oxygen-uptake rate in the microbial culture, was chosen. If the equilibrium is disturbed by changes in OAR, then the oxygen-uptake rate is changed by substrate limitation. The DOC is measured by means of a Clark-type polarographic electrode, and the signal is used to actuate the substrate inflow valve or pump. The oxygen-uptake rate changes of microorganisms, after the addition or exhaustion of substrate in the medium, are so rapid that they can be used for this type of control.Fundamental equations were derived and graphical solutions for the control system parameters were suggested for the steady-state relations between DOC, oxygen-uptake rate, specific growth rate, substrate concentration, KLU, and conrentration of microorganisms. The system is stable in the entire range of the uptake rates up to nearly the maximum attainable in unlimited substrate conditions, and can be operated in batch feed or continuous flow modifications. It was experimentally tested with the yeast Saccharomyces cerevisiae. The complete utilization of aeration-system capacity of the fermentor was achieved with high yeast yield arid no alcohol formation. The quality of the product was excellent.

Optical method for the determination of the oxygen‐transfer capacity of small bioreactors based on sulfite oxidation

“…A good review about the published methods for different chemical and microbial model systems is given by Sobotka et al (1982). The described methods are often divided into two groups according to their applicability either to chemical model systems (Bartholomew et al, 1950;Cooper et al, 1944;Lara Marquez et al, 1994;Linek, 1966;Morimoto et al, 1979) or to microbial systems (Anderlei and Büchs, 2001;Bandyopadhyay et al, 1967;Duetz et al, 2000;Henzler and Schedel, 1991;Hirose et al, 1966;Hospodka, 1966;McDaniel and Bailey, 1969).…”

Growth characteristics of Saccharomyces cerevisiae S288C in changing environmental conditions: auxo-accelerostat study

“…The low glucose concentrations in the feeding enabling steady state at l max in chemostat can result in incomplete glucose repression of citrate cycle (Frick and Wittmann 2005) and thus may affect the calculations of ATP production rate. Using auxostat cultures-turbidostat (Bryson and Szybalski 1952) or the modifications of the turbidostat such as CO 2 -, pH-and pO 2 -auxostat techniques (Hospodka 1966;Watson 1969;Rice and Hempfling 1985;Bü ttner et al 1986;Drews et al 1998) the effect of environmental factor can be studied on both growth yield and rate. We have modified pH-auxostat, CO 2 -auxostat and pO 2 -auxostat for quantitative growth characterization in changing growth conditions Kasemets et al 2003) by introducing computercontrolled smooth changes in selected environmental conditions (auxo-accelerostat).…”

Modelling of Cells Bioenergetics

“…This method of glucose dosing is based on the control of the substrate addition by the oxygen-absorption rate (Hospodka 1966). When a portion of glucose was dosed, the rate of dissolved O 2 uptake by the cells increased, due to a rise in the respiratory activity of the cells.…”