Patent ID: 8859245

Claim:
A method for producing oligo (lactic acid) from a lactic acid fermentation liquor, comprising the steps of: providing a lactic acid fermentation liquor having a pH of greater than 4.8 of lactic acid fermentation by a microorganism, removing cells of the microorganism from the lactic acid fermentation liquor, and adjusting the pH of the lactic acid fermentation liquor to 4.8 or less; adding at least one solvent selected from the group consisting of toluene, xylene, mesitylene, ethylbenzene, and mineral spirit, to the lactic acid fermentation liquor with a pH of 4.8 or less; heating the solvent added lactic acid fermentation liquor with concurrent agitation for azeotropy and then to a temperature ranging from the azeotropic point of the solvent and water to 150° C., whereby the fermentation liquor is dehydrated and a lactic acid component in the fermentation liquor is condensed to produce oligo (lactic acid) with a weight-average molecular weight of not greater than 5000; heating the solvent added fermentation liquor which contains the oligo (lactic acid) with agitation to a temperature ranging from 60° C. to 150° C. to dissolve the oligo (lactic acid) in the heated solvent for extraction; stopping the agitation while keeping the heating to separate the solvent in which the oligo (lactic acid) is dissolved from the fermentation liquor; and cooling down the separated solvent to near room temperature to precipitate and collect the oligo (lactic acid).