PURPOSE: To efficiently recover a metabolite or a reactional product from an aqueous phase by filtering a microbial reactional solution comprising a microorganism, an oil and water through a ceramic filter module and separating a microbial cell/oil from water.

CONSTITUTION: A microbial reactional solution of an oily and aqueous two-phase system in production, etc. of 2,6-naphthalenedicarboxylic acid by culturing Sphingomonas pauclmobilis AK2M16 (FERM P-13996) is filtered through a ceramic filter module. Thereby, the aqueous phase can selectively be separated without containing a microbial or an oil in the separated aqueous phase. The reactional product can readily be recovered in high yield.