Technical support of aerobic fermentation processes

Abstract

The article shows that aerobic fermentation of sugar-containing media requires the presence of dissolved oxygen in them. In most cases, the latter condition is fulfilled by the introduction and dispersion in the liquid phase of the air, which is compressed to levels corresponding to hydrostatic pressures with some exaggeration. The formation of the dispersed gas phase is accompanied by the interaction of the inlet air and the liquid phase, the efficiency of which is determined by the formed contact surface. The study presents generalizations that relate to the dynamics of biomass growth and correlate with the amount of oxygen introduced into the system. It is important that oxygen refers to gases with limited solubility, and therefore the hydrodynamic state and the interfacial surface are among the factors of intensification of mass transfer processes. It is also shown that the nominal estimation of the hydrodynamic state of gas-liquid media should begin with an assessment of the aeration intensity and it is proposed to take the reduced gas phase velocity as the ratio of the volume air flow to the cross-sectional area of the apparatus. Turning to the indicator of the reduced speed negates the influence of geometrical parameters in the form of the ratio of height and diameter. The results of the process and the efficiency of the equipment used are determined by the performance indicators in the form of concentrations of microorganisms and the output rate of the input power supply. The combination of these requirements leads to the need to combine the maximum achievable concentrations of dissolved oxygen and the minimum concentrations of sugars. The features of the double influence of ambient temperatures in the manifestations of the optimal for microorganisms and for the solubility of gases in accordance with Henry's law are shown, the values of Henry constants are given. The list of factors of influence includes such physical parameters of the environment as viscosity, surface tension, osmotic pressure, hydrostatic pressure, temperature. It is determined that the presence of dissolved nitrogen has an influence on the hydrodynamics of gas-liquid media due to changes in hydrostatic pressure in the circulation circuits.