Cells of lactic acid bacteria, which have been obtained by controlling pHs of media in a culturing step and processing steps to a neutral range of, for example, from 5 to 8 or so, have a mode value (particle size) of 1.0 µm or smaller in their particle size distribution. Cells of nano-sized lactic acid bacteria which have such a small particle size are excellent in INF-± producing capacity and are also superb in water dispersibility.
