Rhodotorula mucilaginosa Lysate as a Functional Additive for Serum-Free Culture: Alleviating Lysophosphatidylcholine-Associated Apoptosis

Serum-free culture is fundamental to the sustainable development of cellular agriculture and biomanufacturing. However, serum deprivation often impairs cell survival and culture performance, thereby limiting practical application. In this study, Vero cells served as a mammalian cell model to investigate the relationship between metabolic disturbance and apoptosis under serum-free conditions and to screen microbe-derived supplements with protective potential. Untargeted metabolomics combined with phenotypic and molecular analyses showed that serum deprivation was accompanied by significant intracellular lysophosphatidylcholine accumulation, alterations in the Bcl-2/Bax/Caspase-3 apoptotic axis, and increased apoptosis. Screening of microbial candidates showed that the lysate of Rhodotorula mucilaginosa I7Y2 alleviated these alterations and improved cell viability, proliferation, and wound-healing ability. Incorporation of the lysate into an in-house serum-free medium achieved cell density and apoptosis rates comparable to those in serum-containing medium. Overall, this study provides new insight into the metabolic alterations associated with serum-deprivation-induced cell apoptosis and offers a microbial resource-based strategy for improving serum-free culture performance.