To provide a method for sepn. of mycobiont which easily and accurately quantitatively determines the concn. of the high-polymer flocculating agents in liquid, controls the amt. of the remaining high-polymer flocculating agents and enables the exact design of the refining process for fermentation products in the method for separating the mycobiont by adding the high-polymer flocculating agents having a cationic property to the liquid contg. the fermentation products and the mycobiont.

The high-polymer flocculating agents are at least partly the high-polymer flocculating agents formed by chemically bonding fluorescent materials. The high-polymer flocculating agents remaining in the liquid are quantitatively determined by measuring the fluorescent light intensity of the liquid after the sepn. of the mycobiont. Such fluorescent materials include, for example, 7chloro-4-nitrobenzoxadiazol, 4-(N,N-dimethylaminosulfonyl)-7 fluorobenzooxadiazol, 4-fluoro-7-nitrobenzofurazane,5dimethylaminonaphthalene-1- sulfonyl chloride, 2-p-chlorosulphenyl3-phenylindone, etc.