PURPOSE: To provide a stable single phased liq. of a water-in-oil microemulsion for providing a basic principle for executing reaction based on microorganisms prepd. by adding the microorganisms (a part of them) water soln. into a raw oil (a purified product) and solubilizing them.

CONSTITUTION: The objective single phased liq. is prepd. by adding a water soln. of microorganisms such as thiobacillus, ferroxydance, escherichia.coli, cyanobacteria and saccharomyces and/or a part of the microorganisms into a raw oil and/or a purified product of the raw oil and solubilizing them. In addition, it is pref. that pref. 0.5-15 wt.% surfactant is compounded into crude oil and/or the refined product.