Citric acid, from molasses

Khurshid S, Ali S, Ashraf H, Qadeer M, Rajoka Ml. Mutation of Aspergillus niger for hyperproduction of citric acid from black strap molasses. World J Microbiol Biotechnol 2001 17 35-7. 

Historically, citric acid was isolated by crystallization from lemon juice and later was recognized as a microbial metabohte. This work led to the development of commercial fermentation technology (13). The basic raw materials for making citric acid include com starch, molasses (sugar cane, beet sugar), and normal paraffin hydrocarbons. 

Citric acid fermentation of cane-molasses is by submerged fermentation in a 21 biostat (B. Braun) stirred fermenter. A strain of Aspergillus niger is the most widely used for commercial production. A. niger is also highly recommended in the present study, which can obtained from the American Type Culture Collection, Rockville, Maryland, USA. Molasses... 

Aspergillus niger XTCC 11414 can be used for citric acid fermentation. It should be ordered from the ATCC. The culture was maintained on 10.0% sterilised molasses obtained from Central Sugar SDN BHD, pH 5.8. The slant stock cultures of A. niger will be stored at 5 °C in the refrigerator. All the culture media, unless otherwise stated, is sterilised at 121 °C (15 psig pressure) for 15 minutes. 

Citric acid, which prior to 1922 was made entirely from citrus fruits and mainly in Italy, is now produced almost exclusively by the fermentation of sucrose by means of a mold, Aspergillus niger. At first pure sucrose was used for this process but more recently molasses has been used instead. Practically the whole of the world production of citric acid is used as such in medicinal preparations, in making soft drinks and in certain foods. The textile industries use small amounts, and it is also... 

Malic and citric acids have been adequately identified from molasses as their crystalline hydrazides.119 It is probable that at least the former is a normal juice constituent. Lactic acid was identified as its zinc salt in molasses119 it arises from bacterial action. Formic acid is present119 it probably has an origin, at least in part, in sugar decomposition. Acetic and propionic acids are components and their amounts serve as a rough index of the activity of the microorganisms introduced into the molasses. The microbial count of cane juice, molasses and related products has been determined (Table IV).190... 

Once mycelia have been separated via continuous filtration from exhausted production media, citric acid may be recovered by using three different methods, such as direct crystallization upon concentration of the filtered liquor, precipitation as calcium citrate tetrahydrate, or liquid extraction. Since molasses are extremely rich in impurities, direct crystallization cannot be applied unless very refined raw materials, such as sucrose syrups or crystals, are used. The precipitation process (that is based on subsequent addition of sulfuric acid and lime to clarified fermentation broths) is used by the great majority of world citric acid manufacturers, including Archer Daniels Midland Co. (ADM) in the United States. Liquid extraction with mixtures of trilaurylamine, n-octanol, and Cio or Cn isoparaffin was used by Pfizer Inc. in Europe and Bayer Co. (formerly Haarmann Reimer Co., subsidiary of Miles) in the Dayton (OH, USA) and Eikhart (IN, USA) plants only (Moresi and Parente, 1999), even if such plants might have been shut down in 1998. 

Citric acid, II, 148 III, 238, 242, 248 Iahelled with C11, III, 238 labelled with isotopic C, III, 241 from molasses, IV, 336 from sucrose, IV, 322, 324 Citric acid cycle, in carbohydrate oxidation, III, 238... 

Citric acid occurs naturally in a number of plant species and may be extracted from lemon juice, which contains 5-8% citric acid, or pineapple waste. Anhydrous citric acid may also be produced industrially by mycological fermentation of crude sugar solutions such as molasses, using strains of Aspergillus niger. Citric acid is purified by recrystallization the anhydrous form is obtained from a hot concentrated aqueous solution and the monohydrate from a cold concentrated aqueous solution. 

Finally, microorganisms also produce ingredients for foodstuffs, such as in citric acid fermentation in which citric acid is obtained from molasses using a mould. 

Use Feed, food, raw material for various alcohols, acetone, citric acid, and yeast propagation. Sodium glutamate is made from Steffens molasses, a waste liquor from beet sugar manufacture. 

Ikram-ul H, Ali S, Qadeer M, Iqbal J. Citric acid production by selected mutants of Aspergillus niger from cane molasses. Bioresour Techno 2004 93 125-30. 

The levels of the trace metals in the medium all have a crucial effect on the yield of citric acid, and the concentrations of copper, manganese, magnesium, iron, zinc and molybdenum all need to be controlled. For this reason the fermenter pans are constructed of aluminium or stainless steel to prevent the corrosive solution of citric acid leaching metals into solution. The metals are also removed from the molasses. They are either adsorbed onto ion-... 

Tricarboxylic acid, known as aconitic acid (prop-1-ene-1,2,3-tricarboxylic acid, also known as achilleic or citridinic acid), occurs in two geometric isomers, the (Z)- and the (E)-isomers (8-64). (Z)-Aconitate is widespread as an intermediate produced in the isomerisation of citrate to D-isocitrate (catalysed by aconitase) in the citric acid cycle. About 5% aconitic acid is found in molasses from cane sugar production, where the (E)-isomer prevails, as it is formed by isomerisation of (Z)-aconitic acid at elevated temperatures and low pH. The amount of (Z)-aconitic acid in the growing cane is low, because it is used in the citric acid cycle and not stored in the plant. Decarboxylation of aconitic acid at elevated temperatures yields itaconic acid. 

The optically inactive citric acid (8-67) is the most important representative of tricarboxylic hydroxy acids. Citric acid, as well as malic acid, occurs in many fruits (especially in lemons). Industrially, it is obtained from lemon juice or produced by fermentation of molasses using fungi Aspergillus niger. Along with malic acid, citric acid is used as an additive in widely different canning products... 

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