Two system for monitoring and control of gases from solid-state cultures have been developed The first involves on-line automated monitoring of CO2 and O2 concentration in exhaust gases from eight fermenters or eight gas sampling ports in a large fermenter. It proved to be efficient in obtaining information on the physiological state and respiration rate of the culture in a real-time process. Furthermore, the specific growth rate (mu) can be estimated reliably by gas measurements in aerobic cultures. The second system is for automated control of exit gases from aerobic solid-state fermentations. It permitted elimination of biomass and temperature gradients in a large fermenter due to the maintenance of culture under non-limiting conditions on oxygen. These two systems have applicability in aerobic and anaerobic solid-state processes and were found to be reliable in a number of fermentation experiments as well as optimization of solid-state fermentation. To our knowledge no earlier report of such versatile and reliable on-line automated monitoring/control systems has appeared