Sustainable Production of Added-Value Metabolic Compounds Under Adverse Culture Conditions by Microorganisms: A Case Study of Yarrowia lipolytica Strain Cultivated on Agro-Industrial Residues

Within the framework of sustainability, the parallel valorization of two challenging industrial (crude glycerol) and agricultural (olive mill wastewaters—OMWs) residues by the yeast Yarrowia lipolytica was examined. The rationale of this study was to evaluate the potential of the Y. lipolytica strain ACA-YC 5031 to produce valuable metabolites under a wide range of pH values and increasing NaCl concentrations in agro-industrial blends. OMWs were used as both microbial substrate and process water, and despite high levels of phenolic compounds in the medium and the simultaneously high initial concentrations of NaCl, appreciable quantities of dry cell weight (DCW) and metabolites were synthesized. Moreover, the growth of the strain under non-aseptic conditions was examined. The simultaneous effect of low pH (3.0) and the presence of OMWs (~2.0 g/L) notably increased the extracellular production of erythritol and the accumulation of cellular lipids (reaching Erymax = 18.3 g/L and DCW = 38.6% w/w, respectively). In media with low pH (3.0) and high NaCl concentration (5.0% w/v), a metabolic shift towards erythritol secretion was observed (Erymax = 27.2 g/L, with YEry/Glol = 0.46 g/g). Oleic acid accumulation was enhanced by OMW presence in the medium.