GB266414A - Improvements in and relating to processes for the production of citric acid - Google Patents

Abstract

266,414. Fernbach, A., Yuill, J. L., and Rowntree & Co., Ltd. Oct. 26, 1925. Citric acid; calcium citrate.-The production of citric acid from solutions of sucrose by means of moulds or fungi is carried out without sterilization of the solution by heat but with the addition to the solution of hydrochloric acid, the amount of acid added being such as to establish a hydrogen ion concentration at which the selected 'organisms can be grown to the virtual exclusion of invading organisms; a suitable hydrogen ion concentration is pH 1.8. The solution may be heated for purposes other than sterilization, for example to bring it to the desired temperature of incubation or to establish convection currents and so ensure contact between the whole, of the solution and the ferment. This latter object may be attained also by pumping or stirring the solution or by rotating the container. The process may be carried out continuously by adding further amounts of sugar and/or nutrients continuously or intermittently during the fermentation, with or without the withdrawal of citric acid liquor. The preferred moulds or fungi are darkcoloured aspergilli, and to select a suitable strain a number of these are cultivated on a preferably neutral medium favouring the growth of spores, such as a medium rich in starch. Small amounts of sugar solution acidified with hydrochloric acid and containing nutrients are then inoculated with the spores and incubated, and sub-cultures are made to the required amount from those cultures which give good yields of citric acid. In the preferred process, a solution of sucrose of 10- 20 per cent strength is treated with nutrient materials and with the necessary amount of hydrochloric acid, and is then inoculated with the ferment and incubated at 10-40‹ C. until the content of citric acid no longer increases. The liquor containing, besides citric acid, some starch and residual sucrose may then be subjected to alcoholic fermentation, the starch being first hydrolysed and the liquor rendered suitable for alcoholic fermentation, for example by dilution or addition of fresh nutrients. Alternatively, the liquor may be used or concentrated directly or mav be neutralized with chalk &c. and the citric acid recovered from the calcium &c. salt. Specification 266,415 is referred to.