PURPOSE: Ethanol is added to the turbid concentrate from an acetic fermentation mixture to precipitate the turbid substances, which is removed by filtration or centrifugation, whereby the filtration of the turbid substances with usual filtering paper is made possible without use of a filter aid.

CONSTITUTION: To the turbid concentrate resulting from clarification of an acetic fermentation mixture through ultrafiltration, is added ethanol and they are stirred to coagulate and precipitate the turbid substances. The upper supernatant is used to prepare the starting mixture for the acetic fermentation. The procipitation part is filtered or centrifuged for removing the turbid substances, resulting in a clear liquid. The amount of the ethanol added to the turbid concentrate is preferably 40W60% and, when it is outside the range, the coagulation and precipitation of acetobacter, i.e., the major part of the turbid substances, are lowered. The coagulation and precipitation are promoted by adding a trace amount of alkali or inorganic salt, preferably magnesium or sodium sulfate.