Understanding Fermentation: Bacteria vs. Yeast
Fermentation is a natural process where microorganisms convert carbohydrates into alcohol, gas, or organic acids. The resulting products depend entirely on the microorganisms involved. Understanding the key difference between bacteria and yeast is crucial to knowing what ferments natto.
Bacterial Fermentation
Bacteria are prokaryotic, single-celled organisms that ferment food in a variety of ways. Lactic acid bacteria (LAB), for instance, convert sugars into lactic acid, which is responsible for the tangy taste of foods like yogurt, sauerkraut, and pickles. The type of bacteria used in natto, Bacillus subtilis natto, is different and results in a unique set of compounds.
Yeast Fermentation
Yeast, a type of fungi, are eukaryotic organisms, meaning they have a nucleus. They typically ferment sugars into alcohol and carbon dioxide. This process is essential for making products like bread, beer, and wine. The end product of yeast fermentation is markedly different from the outcome of the bacterial fermentation used to make natto.
The True Microorganism Behind Natto: Bacillus subtilis natto
Contrary to what the misleading term "natto yeast" might suggest, natto is fermented by a specific strain of bacteria: Bacillus subtilis natto. This heat-activated, spore-forming bacteria is naturally found in rice straw and is responsible for all the distinctive characteristics of natto.
How Bacillus subtilis natto Creates Natto
The manufacturing process for natto involves several steps, all orchestrated by this powerful bacterium:
- Boiled soybeans are inoculated with a pure culture of Bacillus subtilis natto.
- The inoculated beans are placed in a warm, humid environment (around 40°C) for 16–24 hours, where the bacteria multiply and propagate.
- During this incubation, the bacteria break down the proteins in the soybeans, creating the sticky, stringy polymer (γ-polyglutamic acid) and a potent enzyme called nattokinase.
- After fermentation, the natto is cooled to halt the process and mature the flavor.
The Myth of “Natto Yeast”
The confusion surrounding "natto yeast" likely stems from misinterpretations of the fermentation process. While some online sources and even older Japanese texts may use this phrase, scientific analysis has definitively identified Bacillus subtilis natto as the agent of fermentation. It is important to remember that "natto yeast" is not a yeast but a bacteria, and consuming natto will not introduce yeast into your gut biome.
Comparison of Fermented Foods
To better illustrate the role of different microorganisms, here is a comparison of natto with other common fermented foods.
| Food | Microorganism | Fermentation Type | Primary Resulting Compounds |
|---|---|---|---|
| Natto | Bacillus subtilis natto (Bacteria) | Bacterial | Gamma-polyglutamic acid, Nattokinase |
| Sourdough Bread | Saccharomyces cerevisiae (Yeast) and Lactic Acid Bacteria | Bacterial and Yeast | Carbon dioxide, Lactic Acid |
| Yogurt | Lactobacillus and Streptococcus (Bacteria) | Lactic Acid Bacterial | Lactic Acid |
| Kombucha | Symbiotic Culture of Bacteria and Yeast (SCOBY) | Bacterial and Yeast | Acetic acid, various organic acids, ethanol |
| Sauerkraut | Lactobacillus and other bacteria | Lactic Acid Bacterial | Lactic Acid |
The Probiotic Benefits of Natto (And Why It Doesn't Need Yeast)
Natto's health benefits are tied directly to the action of Bacillus subtilis natto, which contributes to a wide array of nutritional advantages.
Benefits of Bacillus subtilis natto
- Enhances Gut Flora: B. subtilis natto reaches the intestines alive and helps balance the microflora by promoting the growth of other beneficial bacteria like lactic acid bacteria.
- Inhibits Harmful Bacteria: This bacterium produces antimicrobial substances, actively inhibiting the growth of harmful intestinal pathogens.
- High Survivability: Spore-forming nature makes B. subtilis natto resilient against stomach acid, ensuring it survives the digestive process to reach the gut.
General Health Benefits of Natto
- Boosts Digestive Health: Rich in both probiotics and prebiotic fiber, natto supports a healthy digestive system and regular bowel movements.
- Supports Heart Health: The enzyme nattokinase is a powerful fibrinolytic agent that helps dissolve blood clots, promoting better circulation and lowering the risk of heart disease.
- Enhances Bone Health: Natto is one of the most concentrated food sources of Vitamin K2 (menaquinone-7), which plays a crucial role in regulating calcium and promoting bone growth.
Is Natto a Safe Option for Yeast-Sensitive Diets?
For individuals with yeast sensitivities or those following a diet designed to reduce yeast intake, natto is a suitable and beneficial food choice. Since its fermentation is bacterial, it does not contain the yeast that can trigger sensitivities. This makes it a great way to obtain probiotics and other nutrients without exposure to yeast.
Conclusion
In summary, the answer to the question "does natto have yeast in it?" is a definitive no. Natto is a product of bacterial fermentation driven exclusively by Bacillus subtilis natto. This powerful bacterium, not yeast, is responsible for creating natto's distinctive texture, flavor, and potent health benefits, including enhanced gut health and cardiovascular support. For anyone seeking a yeast-free, probiotic-rich food, natto is an excellent and nutritious choice. Its bacterial fermentation pathway sets it apart from yeast-fermented foods and underscores its unique position as a healthy and safe addition to many diets.
Is Natto Suitable for a Low-Yeast Diet?
Yes, because natto is fermented by bacteria, not yeast, it is completely suitable for a low-yeast or yeast-free diet and can provide significant health benefits.
