Requalified bovine milk as a sustainable supplement for cell cultures

Fetal bovine serum (FBS) is the primary supplement in cell culture practice, although its use raises both ethical and biomedical issues. Obtaining FBS is disrespectful of animal welfare; moreover, its production is affected by unpredictable supply, leading to cost fluctuations. Bovine milk consists primarily of water, fats, proteins, and carbohydrates, also containing various bioactive molecules, partially overlapping with FBS ones. Unsold or expired milk maintains its nutritional properties; thus, we addressed our efforts to its employment to produce a sustainable supplement for cell cultures, thereby reducing FBS usage. Different milk-derived fractions were obtained starting from high-quality fresh pasteurized milk through a multi-step separation process. First evaluations on the HeLa cells showed that various fractions were able to sustain either complete or partial cell development, while others did not allow survival. The presence of α-lactalbumin and β-lactoglobulin was strongly required to promote cell viability. Also, the presence of certain growth factors, including IGF-I, IGF-II, TGFβ1, and TGFβ2, influenced cell growth. Pretreated Fraction 2 (PF2), which resulted in the best-performing fraction, was further tested on additional in vitro models: C2C12 cells, involved in cultured meat research, and Vero cells, a well-known platform for vaccine production. PF2 sustained C2C12 cell development, although the growth kinetics was slower compared to FBS. Instead, in Vero cells, PF2 contributed to a reduction in FBS usage. Thus, the employment of milk-derived fractions as cell culture supplements represents a new opportunity for an ethical transition of cell culture-based studies and, beyond its cost-effectiveness, perfectly fits with sustainable and bioeconomy requirements.