Supercritical carbon dioxide (scCO 2 ) has been investigated for the generation of valuable waxy compounds and as an added-value technology in a holistic maize stover biorefinery. ScCO 2 extraction and fractionation was carried out prior to hydrolysis and fermentation of maize stover. Fractionation of the crude extracts by scCO 2 resulted in wax extracts having different compositions and melting temperatures, enabling their utilisation in different applications. One such fraction demonstrated significant potential as a renewable defoaming agent in washing machine detergent formulations. Furthermore, scCO 2 extraction has been shown to have a positive effect on the downstream processing of the maize stover. Fermentation of the scCO 2 extracted maize stover hydrolysates exhibited a higher glucose consumption and greater potential growth for surfactant (in comparison with non-scCO 2 treated stover) and ethanol production (a 40% increase in overall ethanol production after scCO 2 pre-treatment). This work represents an important development in the extraction of high value components from low value wastes and demonstrates the benefits of using scCO 2 extraction as a first-step in biomass processing, including enhancing downstream processing of the biomass for the production of 2 nd generation biofuels as part of an integrated holistic biorefinery.

Microbial production of biosurfactants represents one of the most interesting alternatives to classical petrol-based compounds due to their low toxicity, high biodegradability, and biological production processes from renewable bioresources. However, some of the main drawbacks generally encountered are the low productivities and the small number of chemical structures available, which limit widespread application of biosurfactants. Although chemical derivatization of (microbial) biosurfactants offers opportunities to broaden the panel of available molecules, direct microbial synthesis is still the preferred option and the use of engineered strains is becoming a valid alternative. In this multidisciplinary work we show the entire process of conception, upscaling of fermentation (150 L) and sustainable purification (filtration), application (foaming, solubilization, antibacterial), and life cycle analysis of acetylated acidic sophorolipids, directly produced by the Starmerella bombicola esterase knock out yeast strain, rather than purified using chromatography from the classical, but complex, mixture of acidic and lactonic sophorolipids.

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