A scalable bubble‐free membrane aerator for biosurfactant production

The bioeconomy is a paramount pillar in the mitigation of greenhouse gas emissions and climate change. Still, the industrialization of bioprocesses is limited by economical and technical obstacles. The synthesis of biosurfactants as advanced substitutes for crude‐oil‐based surfactants is often restrained by excessive foaming. We present the synergistic combination of simulations and experiments towards a reactor design of a submerged membrane module for the efficient bubble‐free aeration of bioreactors. A digital twin of the combined bioreactor and membrane aeration module was created and the membrane arrangement was optimized in computational fluid dynamics studies with respect to fluid mixing. The optimized design was prototyped and tested in whole‐cell biocatalysis to produce rhamnolipid biosurfactants from sugars. Without any foam formation, the new design enables a considerable higher space–time yield compared to previous studies with membrane modules. The design approach of this study is of generic nature beyond rhamnolipid production. In fermentation processes, air bubbles are sparged through the bioreactor (left). By biosynthesis of amphiphilic products as surfactants, the product accumulates in the gas/fluid interphase and leads to tremendous foaming. Due to in situ integration of the here presented membrane module, gas is supplied via permeation through the membrane and therefore bubbleless (right). By this, a foam‐free microbial fermentation is achieved.