Production of Vitamin K2 Enriched Dairy Cream by Bacillus subtilis Natto Fermentation

Foods containing suitable amounts of vitamin K2 and nattokinase have several positive health effective properties. Therefore, in the present research, dairy cream was used as a widely consumed food product for fermentation with Bacillus subtilis natto (BSN) to introduce a new dairy product to the consumers. For this purpose, pasteurized dairy cream (30% fat) was inoculated with BSN and fermented at different temperatures (30°C and 37°C) and incubation times (12, 24, and 36 h) before being stored at refrigeration temperature (4°C). The fermented cream samples were evaluated for protein, ammonium content, protease activity, pH, acidity, nattokinase activity, vitamin K2 (menaquinone-4, menaquinone-7), and total microbial count during the process. The optimal fermentation conditions were found to be at 30°C for 24 h, during which the content of menaquinone-4 (MK-4) and menaquinone-7 (MK-7) increased from 10.92 to 142.27 ng/g and from 4.10 to 43.93 ng/g, respectively. Moreover, fermentation of cream with BSN led to a significant reduction in free ammonium (from 186.84 to 128.36 mg/100 g), and a pronounced increase in protease activity (from 0.003 to 0.328) in the optimum sample. Additionally, all cream samples inoculated with BSN showed a significant reduction (p < 0.05) in total microbial counts throughout the storage period. Sensory evaluation revealed that fermentation did not cause any undesirable properties in the prepared samples compared to the control sample. These findings demonstrate that BSN fermentation is an effective strategy to convert plain dairy cream into a functional product enriched with vitamin K2 and nattokinase, offering a promising innovation for the dairy industry.