Novel membrane stirrer prevents excessive foaming in rhamnolipid production

Introduction

Biosurfactants such as Rhamnolipids (RLs) are naturally occurring amphipathic surface-active agents produced by microorganisms as yeast and bacteria. RLs are eco-friendly alternatives to petrochemical-derived synthetic surfactants with wide-ranging applications across various industries including environment, petroleum, agriculture, food and pharmaceuticals.

Apart from the typical microbial cultivation challenges, producing biosurfactants is especially prone to extensive foaming. When gas bubbles are introduced into the fermentation broth, the biosurfactants adsorb at the gas-liquid interfaces, forming bubbles with micelles stabilizing the foam (see Fig. 1). Foaming in bioprocesses can reduce product quality and quantity (e.g., by protein denaturation) as well as productivity and result in a loss of the whole-cell biocatalyst [2–4]. In this application note, fermentation experiments using Pseudomonas putida KT2440 SK4 strains were conducted to establish a benchmark comparing RL titers in the BioThrust MemStir with a conventional stirred-tank reactor (STR) at a 2 L scale. The MemStir demonstrated a space-time yield (STY) of up to 118 mg_RL L^-1 h^-1, ranking it high in industrial RL production with both conventional and complex fermentation methods.