Foam Control in Fermentation Bioprocess

Abstract

In this article, we describe the development of a simple laboratory test for the effective screening of foam control agents on a selected fermentation system, the mass production of Yarrowia lipolytica. Aeration testing is based on sparging air in the foaming medium allowing partial reproduction of the gas-liquid hydrodynamic encountered in bioreactors. "Dynamic sparge test," for which measurements are made during foam formation, was used to compare the capacity of three antifoams, based on different technologies, to control the foam produced in the fermentation broth. The selected foam control agents were: (1) an organic antifoam (TEGO AFKS911), (2) a silicone-based emulsion containing in situ treated silica (DC-1520) and (3) a silicone/ organic blend silica-free formulation. The testing results demonstrated dramatic differences among them and showed that the capacity of TEGO AFKS911 and DC-1520 to control the foam generated in the fermentation broth decreases as a function of fermentation time. This occurred to a much lesser extent for the silicone/ organic blend formulation. These results were correlated with the change of the foam nature and the increase of foam stability of the fermentation broth with culture time. The increase in protein content as a function of growth time was correlated with an increase in foam stability and antifoam consumption. A "synthetic fermentation broth" was also developed, by adding both proteins and microorganism to the culture medium. This allowed us to mimic the fermentation broth, shown by the similar antifoams behaviour, and is therefore a simple methodology useful for the selection of appropriate antifoams.

Beyond De-Foaming: The Effects of Antifoams on Bioprocess Productivity

“…Foam occurs in bioprocesses due to the introduction of gases into the culture medium, and is further stabilised by proteins produced by organisms in the culture[1]. Foam is made up of liquid lamellas which are full of gas.…”

“…Additionally, DO in shake flask cultures of P. pastoris was unaffected by the presence of antifoam, suggesting that any changes to k L a were not great enough to influence the DO in the culture[32]. These DO measurements have been performed in various growth media in both the absence and presence of cultures of prokaryotic and eukaryotic microbes[1, 11, 13, 16, 18, 19, 25]. In contrast, literature on the biological effects of antifoams on recombinant protein production by microbial host cells is more limited, suggesting that this area is not routinely considered.…”

Genetic Cell-Surface Modification for Optimized Foam Fractionation

“…An associated accumulation of bacterial cells and medium in the foam causes a loss of homogeneity in the reactor. As homogeneous conditions in the reactor assure an optimal mass and energy transfer, process efficiency declines (Etoc et al, 2006;Lara et al, 2006). Furthermore, foam formation can result in obstruction of filters, valves, tubing, as well as sterility problems in the fermenter (Delvigne and Lecomte, 2010).…”

Cell Density Effects in Different Cell Culture Media and Their Impact on the Propagation of Foot-And-Mouth Disease Virus

“…One problem when launching bioreactors is the formation of foam inside the reactor. Foam originates from stirring, sparging of gas into the liquid and from dead cells and it is a high mechanical burden for viable cells [20,21]. Chemical defoamer interacts with cell membranes [22] and it is therefore possible that antifoaming agents interfere with cell-virus interactions.…”