How is vitamin K2 produced? Exploring Natural and Synthetic Methods

January 13, 2026 •

2 min read

According to the Cleveland Clinic, vitamin K2 is primarily synthesized by bacteria. It is created through processes such as microbial fermentation, large-scale chemical synthesis, and by the microorganisms within the gut. This exploration will cover the distinct methods used to produce vitamin K2 for supplements and food sources.

Quick Summary

Vitamin K2, or menaquinone, is predominantly a product of bacterial synthesis, occurring through natural fermentation or as an industrial process. It can also be produced synthetically or formed by tissue conversion in animals.

Key Points

Microbial Fermentation: Bacteria like Bacillus subtilis and lactic acid bacteria produce K2 in foods like natto and cheese.
Biologically Active Isomer: Fermentation often yields the active all-trans K2 form; chemical synthesis may produce a mix of isomers.
Chemical Synthesis: An industrial method for supplements, requiring purification to isolate active K2 forms.
Endogenous Production: Gut bacteria synthesize K2, but limited absorption means dietary sources are necessary.
Animal Tissue Conversion (MK-4): The body creates MK-4 from K1 or menadione in tissues, a non-bacterial process.
Industrial Optimization: Bioprocessing and engineering enhance both fermentation and synthetic K2 production.

Production via Bacterial Fermentation

Bacterial fermentation is a key natural method for producing vitamin K2, particularly long-chain menaquinones (MK-5 to MK-13). This involves specific microorganisms converting substrates into the vitamin. A well-known example is natto, a fermented soybean dish rich in MK-7, produced using Bacillus subtilis var. natto bacteria.

Fermentation is often preferred for creating biologically active K2 as it naturally yields the all-trans isomer, considered more effective than cis isomers found in some synthetic versions. Other fermented foods like cheeses also contain K2, produced by lactic acid bacteria such as Lactococcus and Lactobacillus species. Industrial production utilizes bioprocess engineering to optimize fermentation conditions for specific menaquinone yields.

Bacteria Known to Produce Vitamin K2

Bacillus subtilis var. natto: Used for natto production, yielding high MK-7.
Lactic Acid Bacteria (LAB): Found in fermented dairy, producing longer-chain MKs like MK-8, MK-9, and MK-10.
Gut Microbiota: Bacteria in the human gut, including Bacteroides and Bifidobacteria, contribute to K2 synthesis, but absorption is limited.

Chemical Synthesis for Industrial Supplements

Chemical synthesis is an industrial process used to produce vitamin K2 for supplements. It involves multi-step chemical reactions to create the vitamin molecule. A challenge with this method is controlling the stereochemistry, often resulting in a mix of active all-trans and less-effective cis isomers. This requires purification to isolate the desired all-trans form. The process uses precursors like menadione.

Endogenous Production by Gut Bacteria

Gut bacteria like Bacteroides synthesize vitamin K2, mainly in the distal colon. However, absorption from this source is limited and insufficient to meet daily needs. Therefore, dietary sources remain crucial for obtaining sufficient, biologically available vitamin K2.

Tissue Conversion in Animals (MK-4)

The shorter-chain form, menaquinone-4 (MK-4), is uniquely produced in animal and human tissues, not by bacteria. The body converts dietary vitamin K1 (phylloquinone) or other precursors like menadione into MK-4 through realkylation. Consequently, MK-4 is found in animal products such as eggs, meat, and some dairy.

Production Methods Comparison: Fermentation vs. Chemical Synthesis


Aspect	Microbial Fermentation	Chemical Synthesis
Mechanism	Bacteria synthesize vitamin K2.	Chemical reactions combine precursors.
Key Outcome	Naturally produces active all-trans form.	Can yield mix of all-trans and cis isomers.
Starting Materials	Natural substrates (soybeans, milk).	Chemical precursors.
Purity	Requires extraction, potential byproducts.	High purity possible after purification of active isomer.
Consistency/Supply	Can vary, but controlled industrially.	Generally more consistent composition.
Sustainability	More sustainable, avoids heavy metals.	Involves chemical reagents, solvents.

Conclusion

Vitamin K2 production involves both natural microbial processes and artificial chemical synthesis. Bacteria, like those in natto and cheeses, are primary natural sources, particularly for long-chain MKs such as MK-7. Fermentation yields the highly active all-trans isomer. Chemical synthesis provides a consistent supply for supplements but requires purification to ensure a high concentration of active isomers. The body also produces MK-4 from K1 in animal tissues. While gut bacteria contribute to K2, dietary intake is vital for sufficient absorption. Understanding these methods helps distinguish K2 sources and quality. For more on microbial vitamin synthesis pathways, consult studies from the National Institutes of Health (NIH).

Frequently Asked Questions

Specific bacteria are used to produce K2 in foods. For instance, Bacillus subtilis var. natto is used in natto, and Lactococcus species are used in cheesemaking.

Vitamin K1 is produced by plants, while vitamin K2 is primarily produced by bacteria through fermentation or synthesized chemically.

Effectiveness depends on the isomeric form; the all-trans isomer is more active. Fermentation naturally produces this form, while chemical synthesis may yield a mixture, requiring purification for high activity.

MK-4 is not a product of bacterial synthesis. It's formed in animal tissues, including human, by converting dietary K1 or menadione.

While gut bacteria do produce some K2, its absorption in the colon is limited, making dietary sources crucial for sufficient levels.

Natto's fermentation process using Bacillus subtilis var. natto results in an exceptionally high concentration of the MK-7 form of vitamin K2.

Fermentation is a more sustainable, natural method for producing K2. It can be optimized to increase yields of desired menaquinones, like MK-7, with a high concentration of the active all-trans isomer.