Systems and methods for controlling biological foam in microbial fermentation.

Abstract

The invention relates to a system and method for controlling biological foam during microbial fermentation, particularly applicable to high-density biomass fermentation without the use of antifoaming chemicals. The system comprises a two-step biological foam separation unit consisting of a primary foam separator cyclone and a secondary foam separator cyclone connected in series, where the secondary cyclone has a diameter ratio D₂ / D₁ from 0.35 to 0.65 and an inner wall structure that generates a hydrodynamic shear stress range from 50 Pa to 120 Pa—sufficient to break the viscous protein membrane of the biological foam but without damaging the microbial cells. The separated biomass is recirculated back to the fermentation tank via a U-trap and damping chamber without the need for mechanical actuators, and the system operates stably with apparent viscosity of the fermentation broth up to 900 mPa·s.The integrated control system uses the first derivative of pressure with respect to time as the trigger signal, coordinating the sequential opening of valves with a defined delay and pausing the pH-adjusting chemical dosing station in each defoaming cycle, then compensating for the deficit according to the equation E = Ki·∫(pH_set − pH_actual)dt. The system according to the invention has been experimentally verified with a volumetric oxygen mass transfer coefficient increased from 40% to 50% and a final batch biomass density increased by approximately 48% compared to the system using defoaming chemicals under the same operating conditions.

Images