What is the primary fermentation technique used for "Kimoto" sake?

The primary fermentation technique used for "Kimoto" sake indeed involves the use of natural lactic acid bacteria. In Kimoto style sake production, the method relies on creating a yeast starter (yeast mash or "moto") that naturally develops lactic acid through the action of wild lactic acid bacteria. This natural process is crucial as it allows for the fermentation to take place in a more traditional and spontaneous manner, as compared to other methods that may utilize added lactic acid or controlled environments.

This approach not only imparts a unique flavor to the sake but also helps in protecting the fermentation process from unwanted bacteria, enhancing the overall complexity of the final product. The rich and robust characteristics that many people appreciate in Kimoto sake can largely be attributed to this natural fermentation process that harnesses the inherent qualities of the rice and the environment.

In contrast to this correct choice, other methods such as using koji mold alone, elevated heat application, or extreme cold fermentation do not accurately capture the essence or methods behind the Kimoto fermentation style, which distinctly emphasizes the role of natural bacteria.