GB974589A - Purification of fermentation broths - Google Patents

Abstract

A fermentation broth is purified to remove cell materials and other impurities therefrom by treating the fermentation broth with calcium hydroxide, converting the calcium hydroxide in the broth into calcium carbonate and separating the calcium carbonate from the broth together with the co-precipitated cell materials and other impurities. The treatment with calcium hydroxide is effected, preferably at an elevated temperature of 70-90 DEG C., by the addition of milk of lime or ground calcium oxide in amounts corresponding to between 0.1 and 10% by weight of calcium oxide calculated on the broth and the conversion to calcium carbonate is made at ambient or elevated temperatures by passing carbon dioxide into the broth or by adding a stoichiometric quantity of an alkali metal (sodium) carbonate. In a preferred procedure the broth is maintained at a temperature of 70-90 DEG C. for from 5-40 minutes prior to the conversion, which is effected in two stages at different pH values, the precipitated substances being removed from the fermentation broth after each stage, as by filtration, centrifuging or decanting. Many fermentation broths are mentioned. According to an example, 3.5 parts of lime were added to 100 parts of a fermentation broth containing 5.5 parts glutamic acid together with bacterial cells. The original pH of the broth was 12.2-12.4. The broth was heated to 75-85 DEG C. and maintained at this temperature, with vigorous stirring, for 10-20 minutes. The pH of the broth was then adjusted to 9.4-9.5 by passing in carbon dioxide, and the temperature was lowered to 50-60 DEG C. The broth was then filtered at this temperature without difficulty. Carbon dioxide was again passed into the filtrate until a pH of 7.7 was reached and the broth was filtered again, yielding a clear solution. Glutamic acid was crystallized from the solution in two crystal crops.