Surfactants represent a large group of industrial relevant substances and can be generated chemically, but also biologically. Important microbial producers are several Pseudomonas species, mainly known for their ability to produce rhamnolipids. For safety reasons, recombinant Pseudomonas putida is preferred for heterologous production of rhamnolipids as well as its precursor 3-(3-hydroxyalkanoyloxy) alkanoic acid (HAA), which is a promising platform substance. The surface-active properties of HAA combined with classical submerged aeration cause strong foam formation making biotechnological production in stirred tank bioreactors challenging. Therefore, a foam-free bioprocess for HAA production was developed in this study. The combination of headspace aeration, overpressure up to 8 bar, and temperature reduction prevented oxygen limitation, shortened process time, and enhanced the maximum HAA concentration to 1.71 g l− 1 with a space-time yield of 0.08 g l− 1 h− 1. Graphical Abstract

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