Oleaginous Yeasts for Sustainable Single-Cell Oil Production: A Critical Synthesis of Metabolism, Feedstocks, Bioprocessing and Scale-Up
O. O. Ayano
Microbiology Unit, Department of Pure and Applied Biology, Ladoke Akintola University of Technology, Ogbomoso, Nigeria.
C. O. Bamigboye *
Microbiology Unit, Department of Pure and Applied Biology, Ladoke Akintola University of Technology, Ogbomoso, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Single-cell oils produced by oleaginous yeasts are frequently proposed as alternatives to plant and fossil-derived lipids because they can be synthesised in controlled bioreactors, can exploit diverse carbon streams and can be compositionally tailored through strain and process engineering. Yet the industrial sustainability of yeast oil is not determined by lipid content alone. It depends on the interaction among carbon-source quality, substrate conversion, lipid titre, yield and volumetric productivity, oxygen and nutrient demand, strain robustness, downstream recovery, product specification, co-product strategy and the assumptions used in techno-economic and life-cycle assessment. This critical narrative review evaluates these interacting dimensions, with emphasis on Yarrowia lipolytica, Rhodotorula toruloides, Lipomyces starkeyi and Cutaneotrichosporon oleaginosus. Literature was selected from accessible scholarly databases and citation networks for the period 2000 to 19 June 2026, while earlier foundational studies were retained where mechanistically necessary. The evidence supports a mature biochemical understanding of nitrogen-limitation-driven lipogenesis and shows that metabolic engineering can markedly increase storage-lipid formation in model conditions. Evidence is also substantial that several oleaginous yeasts can convert lignocellulosic hydrolysates, crude glycerol and other residual streams. The principal weakness is translational: high lipid fractions reported in defined media are often not accompanied by equally strong titre, productivity, tolerance, feedstock reproducibility, extraction performance or system-level environmental evidence. Techno-economic and life-cycle studies consistently identify fermentation productivity, inexpensive carbon supply, energy use and downstream processing as decisive variables, while residue removal and co-product allocation can alter environmental conclusions. The most defensible pathway to sustainable single-cell oil therefore combines robust mixed-substrate biocatalysts, high-cell-density process control, low-energy recovery and product-market matching, with techno-economic and life-cycle analysis embedded during process development rather than added after optimisation.
Keywords: Microbial lipids, lipid biorefinery, waste valorisation, metabolic engineering, lignocellulosic hydrolysate, fed-batch fermentation, lipid recovery, life-cycle assessment