Milk thistle (Silybum marianum) is a plant from the Asteraceae family, originally native to the Mediterranean region, but now also found in other parts of Europe, North America, and Australia. Large, spiny leaves with white spots and purple flowers characterize it. Milk thistle is valued mainly for its silymarin content, which has strong liver-protective properties. The seeds are rich in protein, fiber, healthy fats, and micronutrients, making them a valuable dietary ingredient.
Milk thistle oil cakes, or residues from pressing oil from seeds, can also be a valuable source of many nutrients. This work aimed at analyzing the composition of milk thistle cakes and attempted to valorize them by using them as components of a microbiological medium in cultivating Yarrowia yeast. The main components of the cakes were determined in the work, including the content of dry matter, protein, and fat. The results of the analyses confirmed that milk thistle cakes are a valuable source of fat, in which polyunsaturated fatty acids dominate. Such an oilcake introduced into microbiological media is a valuable carbon and nitrogen source for growing microorganisms. Yarroiwa lipolytica grown on media with 10% addition of oilcake showed high biomass yield and lipolytic activity twice as high as in the control medium (YPG).