Osmotic, biomass, and oxygen effects on the growth rate of Fusarium oxysporum using a dissolved-oxygen-controlled turbidostat

The system described is a modified Hospodka's turbidostat. This device helps to measure the maximum growth rate of fungi in steady-state aerobic conditions with defined and independent concentration of dissolved oxygen, biomass, and substrate even unlimited. The principle consists of a turbidostat controlled by the dissolved oxygen concentration. The inlet medium pump operates when the dissolved oxygen concentration falls below the set point value. This method allows us to study independently effects of different physical and chemical variables on the maximum specific growth rate of microorganisms. A fungus, Fusarium oxysporum 47 isolated from soil, does not show a depressive effect on growth when dissolved oxygen concentration decreases to 5% and osmotic potential to -25 bars. Increasing biomass concentration in the range 0.1-1.0 g/L appears to depress markedly the maximum growth rate.