Direct conversion of dissolved air flotation sludge to mannosylerythritol lipids by <i>Moesziomyces aphidis</i>

Abstract Dissolved air flotation (DAF) sludge from wastewater treatment plants is often a lipid‐rich waste stream, which is now mostly being converted to biogas. Due to its high carbon content, DAF sludge has great potential in biotechnological applications. MEL production with floated grease from a sauce producer as substrate resulted in the accumulation of 1.1 ± 0.1 g/L MEL. With enhanced aeration through the use of baffled shaking flasks, MEL titres increased up to 9.7 ± 0.5 g/L. An adaptation period of 9 days was observed, after which the specific productivity reached 0.20 g/L.h. This study shows for the first time biosurfactant production from DAF sludge, with promising titres. Further research should focus on reducing the lag phase to increase productivity.