Biodiesel production using wild-type oleaginous microorganisms grown on whey: A state-of-the-art review

The global demand for sustainable biofuels necessitates the valorisation of abundant, low-cost feedstocks such as whey, a major and highly polluting dairy industry by-product. This state-of-the-art review critically examines the use of wild-type oleaginous microorganisms (microalgae, yeasts, and bacteria) for converting whey into microbial lipids suitable for biodiesel production, focusing on non-genetically modified strains. Our synthesis of current knowledge highlights that oleaginous yeasts (e.g., Cutaneotrichosporon oleaginosus) achieve the highest reported lipid yields, exceeding 38 g L−1 with optimized whey permeate supplementation. Most importantly, literature evidence suggests that the best way to overcome the intrinsic nitrogen limitation of whey is two-stage fed-batch fermentation, which effectively decouples growth and lipogenesis, representing a significant technical advancement toward high lipid production. Furthermore, this review establishes that economic feasibility and environmental impact reduction are contingent upon a full biorefinery approach, integrating lipid production with the co-generation of valuable metabolites, such as proteins and polysaccharides. Collectively, this review establishes a comprehensive framework for leveraging robust wild-type oleaginous strains to shift whey valorisation from an environmental liability to a competitive, circular bioeconomy strategy, provided that remaining scale-up and downstream processing bottlenecks are addressed.