NON-CONVENTIONAL YEASTS AS CELL FACTORIES: FROM FOOD WASTE TO ADDED-VALUE PRODUCTS.

In the context of circular economy and green chemistry, non-conventional yeasts are known as efficient ‘cell factories’ for the synthesis of value-added products. The incorporation of industrial food waste in fermentation and biocatalytic processes is one of the major challenges in the transition towards a sustainable and low impact bio-economy. This PhD thesis explores the potential of non-conventional yeasts by applying different strategies: - Optimizing a liquid medium exclusively composed of pumpkin peel hydrolyzate, able to efficiently support cell growth and microbial lipid production. In this study, the performances of two oleaginous yeast strains (Rhodosporidiobolus azoricus and Cutaneotrichosporon oleaginosum ATCC 20509) were compared. - Setting an efficient lipid production process employing C. oleaginosum ATCC 20509 strain and starting from liquid cheese whey permeate, a diary by-product that provided nutritional compounds and allowed to save freshwater. In this work, an analytical flow cytometer method was developed for a rapid and sustainable monitoring of lipid accumulation. - Expressing a heterologous adhesin protein (CFL1p) to enhance the flocculating ability of C. oleaginosum ATCC 20509. This reduced the time required for downstream procedures, maximizing the industrial applicability of lipid-rich cells. - Immobilizing a marine yeast strain for the synthesis of perillyl alcohol. In this work, molasses and seawater were used to obtain the biocatalyst biomass employed as whole-cell biocatalysts, which were immobilized in alginate beads to easily scale up the reaction in a rotating bed reactor (SpinChem®). The overall focus of the thesis is to develop and maximize microbial production strategies, making them industrially scalable thanks to low costs, high yielding, and environmentally friendly approaches.