Newly Isolated Kluyveromyces marxianus Strain Capable of Producing Oleic Acid-Rich Oil for Human Consumption from Whey

Cheese whey is a widely available agri-food byproduct whose high organic load presents significant challenges for the dairy industry and environmental management. Its biovalorization into high-value, sustainable functional lipids is increasingly important given the environmental concerns associated with conventional vegetable oil production. This study examines the isolation, identification, and characterization of a wild-type yeast strain capable of synthesizing oleic acid-rich oil from cheese whey. Screening six different sources yielded thirteen microbial isolates capable of growing on whey lactose, of which five demonstrated neutral lipid accumulation. The isolate with the highest lipid content was selected and molecularly identified as Kluyveromyces marxianus CM3b. Batch cultivation of K. marxianus CM3b in whey-based medium reached a maximum biomass concentration of 5.50 ± 0.06 g/L and a lipid concentration of 2.68 ± 0.08 g/L at 24 h, corresponding to a lipid yield of 0.49 ± 0.02 g/g of biomass (approximately 49% w/w) and a 24-h volumetric lipid productivity of 2.68 ± 0.08 g/L·d. The extracted oil contained a high proportion of monounsaturated fatty acids (69.56%), predominantly oleic acid (53.51%), and a fatty acid profile comparable to those of avocado and olive oils. These findings highlight K. marxianus CM3b as a promising wild-type strain for the sustainable production of oleic acid-rich microbial oil from a whey-based substrate. However, further physicochemical characterization and strain-specific safety assessment are required to establish its suitability for food applications.