The effect of sonication and stirring on ultrafiltration of fermentation broth

Membrane separation is a widely used technique whose main obstacle is membrane fouling, during which a solution or particles accumulate on the membrane surface or inside its pores. This phenomenon causes both reversible and irreversible flow resistances that can be minimized with complementary techniques such as sonication and/or stirring. The application of ultrasonic energy can increase the flux by breaking the concentration polarization and cake layer on the membrane surface without affecting the intrinsic permeability of the membrane. Our work focused on cellulase and P-glucosidase enzyme recovery through sonicated/stirred ultrafiltration from the real fermentation broth, at which the fermentation liquid was produced from tobacco plants. Membrane filtrations were carried out in a laboratory-grade batch ultrafiltration cell, extended with stirrer and ultrasound processor. The effects of stirring speed and ultrasound treatment were investigated on the membrane's permeate flux efficiency and on the quality of recycled enzymes. Resistance values were calculated by the resistance-in-series model, as well as by Hermia's analysis, to reveal deeper, process-related information. Our results revealed that enzymes could be efficiently separated from real fermentation broth. Furthermore, the enzyme activity test showed that neither stirred nor sonicated processes were detrimental to the enzyme activity.