Novel biosurfactants produced from food waste: a variability and validation study.

One-third of global food production is wasted, much of which is composted, gasified or landfilled. This food waste (FW) represents an untapped resource, particularly towards the production of biosurfactants. Genetically engineered Starmerella bombicola yeast strains offer a route to produce novel biosurfactants on FW with enhanced structural diversity, such as bola sophorosides. However, FW streams are variable, and often contain inhibitory compounds (e.g. lactic acid (LA), ethanol, etc.), posing bioprocessing challenges. Here we show that hydrolyzed FW consistently supports S. bombicola growth and bola sophoroside production, despite FW variability and high LA concentrations. Linear regression models accurately predicted fermentation outcomes across variable FW batches. Furthermore, the inhibitory effect of LA on biosurfactant production by S. bombicola was significantly reduced by a dedicated pH-control strategy. A proof-of-concept fermentation confirmed that hydrolyzed FW outperformed conventional media, achieving higher biomass (25.27 ± 4.18 vs. 19.71 ± 2.08 g/L) and productivity (0.28 vs. 0.13 g/L/h). In conclusion, this work demonstrates the viability of (variable) FW as a fermentation feedstock, opening new avenues for its valorization towards sustainable bioproducts.