Patent GB-669733-A (GB)
Title: Improvements in the production of citric acid by fermentation of a carbohydrate medium
IPC: C12P7/48
Filed: 1948-03-31
Abstract: A process for the production of citric acid by fermentation of an ash-containing carbohydrate with a citric acid-producing strain of fungus comprises, prior to the fermentation, diluting the ash-containing carbohydrate with water to give a carbohydrate concentration of about 13 to 20 per cent and decationizing the diluted carbohydrate in two steps by passing the diluted carbohydrate through a first bed of cation-exchange resin operating in the H-cycle and then through a freshly-regenerated second bed of cation-exchange resin operating in the H-cycle and further diluting the ash-containing carbohydrate during and after the first of the decationizations to effect a 1-2 per cent dilution, the two decationizations effecting reduction in the Fe content of the decationized ash-containing carbohydrate to between 0.5 and 5.0 p.p.m. with substantially all of the Fe removal being effected in the first decationization step.  The process is described with particular reference to invert molasses of sugar content about 75 per cent is diluted with 3 volumes of water.  The diluted molasses is passed through a bed of regenerated cation-exchange resin.  When the pH of the effluent is about 1.7-1.8 the effluent is collected, the flow rate then being controlled to give an effluent pH of 1.39-1.41.  The collected effluent is 1-2 per cent more dilute than the initial feed, this being caused in part by residual water in the resin bed or by collecting effluent molasses before dilution effects caused by effluent water preceding the molasses have ceased and in part by collecting effluent containing water used to displace residual molasses from the resin bed.  The treated molasses now containing about 15 p.p.m. iron is passed through a freshly-regenerated bed of resin in similar fashion, the effluent being collected with minimum dilution effects to keep the sugar concentration to 13-20 per cent for fermentation.  This second bed may be used subsequently in the first treatment of another batch of diluted molasses.  The decationized molasses is treated with sodium hydroxide to adjust the pH to 2.1-2.8, sterilized and amounts of NH4NO3, MgSO4, KH2PO4 and ZnSO4 are added as nutrients; the zinc content should be 10-30 parts to each part of Fe.  The molasses is then inoculated with A. Niger and fermentation allowed to proceed at about 31 DEG  C. in shallow aluminium pans and the resulting citric acid recovered by conventional procedures.  Other carbohydrate media mentioned are corn syrup, raw sugar juices, beet molasses, citrus molasses, and cane and beet blackstrap molasses.  Additional examples of citric acid producing fungi are A.Clavatus, A. Wentii, A. Leuchensis, P. Citrium, P. Luteum and Mucor Periformis.  Suitable cation-exchange resins are "Amberlite IR-1" and those described in Specifications 450,308 and 474,361.  Specifications 572,383 and, in a disclaimer, 653,808, are referred to.  The Specification as open to inspection under Sect. 91, relates to a citric acid producing fermentation as above using an ash-containing carbohydrate medium which has been contacted with a cation-exchange resin operating in the H-cycle to reduce the Fe content to a tolerable concentration, in particular a value not in excess of 5 p.p.m.  This subject-matter does not appear in the Specification as accepted.