Foam control in biotechnological processes—challenges and opportunities

Abstract

Foam formation is a massive challenge in submerged aerated bioprocesses, e.g., in beer fermentation. While the use of antifoam may easily overcome foaming at laboratory scale, it is often an unattractive solution since the challenge remains in future upscaling, as reduced mass transfer and extra steps in product purification and analytics result in increased costs. Interestingly, the number of studies tackling this challenge is relatively low, although literature suggests a range of alternatives, from avoiding foaming to means of controlling or even using foaming as an in situ product removal. Here we give an overview of the topic in five subsections. (1) We argue that a sound understanding of the molecular origin of foaming can facilitate solutions for overcoming the challenge while introducing some long-known challenges (i.e., in beer fermentation). We then review in (2) the apparent avoidance of foam formation before we in (3) summarize possibilities to reduce and control foam after its formation. Subsequently, in (4), we discuss possible solutions that take advantage of foam formation, for example, via foam fractionation for in situ product removal. Finally, in (5), we provide an overview of microbial strain engineering approaches to cope with some aspects of foaming in fermentations. With this review, we would like to sensitize and inform the interested reader while offering an overview of the current literature for the expert, particularly with regard to the foam special issue in Discover Chemical Engineering.

Synergisms between Surfactants, Polymers, and Alcohols to Improve the Foamability of Mixed Systems

“…At t = 0 min, for the same surfactant concentration, the solutions presented bubbles of smaller size when the polymer was incorporated and at t = 30 min the polymer effect was even more pronounced, with the system betaine/HM-P being the one presenting lower coalescence. It is also possible to observe that the shape of the cells was not spherical but polyhedral, separated by flat liquid films, indicating good foam stability [40,41] with a very small decrease in foam volume, ca. 10 mL for the betaine/HM-P system, after 30 min.…”

Optimized Feeding Strategies for Biosurfactant Production from Acetate by Alcanivorax borkumensis SK2

“…The production of biosurfactants by fermentation faces challenges, with foam formation being the major issue [54]. Foaming can negatively impact the overall process performance, product quality, and quantity and may lead to the loss of biocatalysts already at low product concentrations [55][56][57].…”