Determination of vitamin K and other fat-solublvitamin e levels produced by some microorganisms in kefir

Kefir is a fermented milk product produced using kefir grains. Kefir grains have been used for centuries as a source of probiotics. The importance of probiotics due to their effects on the intestinal and immune systems remains relevant today. Probiotic microorganisms residing in the intestinal flora produce metabolites that have positive effects on our health. This study aimed to determine the levels of fat-soluble vitamins Vitamin A, D, E, K1 and K2 produced by some important probiotic microorganisms in kefir grains using High Performance Liquid Chromatography (HPLC). Particularly, the levels of K1 and Vitamin K2, which are crucial vitamins, were investigated. As a result, Lacticaseibacillus casei was found to have higher levels of Vitamin A, D, and E compared to other microorganisms. In the kefir sample produced with kefir grains, the Vitamin K1 level was determined to be the highest at 0,430 mg/100 g compared to other microorganisms. The Vitamin K1 levels of other microorganisms ranged between 0,077-0,314 mg/100 g. Lentilactobacillus kefiri had the highest Vitamin K2 level among other microorganisms at 0,023 mg/100 g. The Vitamin K2 levels of other microorganisms ranged between 0,009-0,019 mg/100 g. Additionally, Kluyveromyces marxianus had the highest Vitamin K1 level, while the kefir produced with L. kefiri cultures had the highest Vitamin K2 level. These findings contribute to the literature research. It is recommended to study the metabolism and pathways of all vitamins separately, as there is a significant gap in the literature regarding this matter.