For the purpose of providing a method of safely and inexpensively producing a fermented plant extract containing an immunopotentiator at a high concentration, the method for fermentation and culture of the present invention ferments a plant component such as wheat flour using Pantoea agglomerans which is a gram negative bacterium which lives in a symbiotic relationship with a plant such as wheat and apple. It becomes possible to remarkably augment an immunopotentiation action which the plant has. In addition, these are not contaminated with impurities derived from animal components, and thus these are highly safe.
