Citric acid fermentation

Citric acid makes up almost 85% of the total volume of the organic acid market, ft was first described in 1784 when isolated from lemon juice. In 1917, it was discovered that certain fungi accumulate citric acid. In 1923, the first US commercial plant was built to produce citric acid by fermentation citric acid is now used mainly in soft drinks, desserts, jams, jellies, candies, wines and frozen fruits. 

Uses Emulsifier, thickener, wetting agent, dispersant, solubilizer, stabilizer in cosmetics, pharmaceuticals demulsifier in petrol, industry detergent ingred. antistat for polyethylene and resin molding powds. antifoam for sugar beet processing, fermentation, citric acid, yeast Manuf/Distrib. Aldrich Trade Names Tetronic 1301 See also EO/PO ethylenediamine block copolymer... 

Arkenol A complex, integrated process for making ethanol from ceUulosic wastes. It uses concentrated sulfuric acid hydrolysis and microbial fermentation. Citric acid and gypsum are by-products. Developed since 1987 by W.A. Farone of Applied Power Concepts in Anaheim, CA. There are nine granted U.S. patents. A small plant was built in Japan in 2002 in association with JGC. Commercial development is now controlled... 

Citric Acid Separation. Citric acid [77-92-9] and other organic acids can be recovered from fermentation broths usiag the UOP Sorbex technology (90—92). The conventional means of recovering citric acid is by a lime and sulfuric acid process ia which the citric acid is first precipitated as a calcium salt and then reacidulated with sulfuric acid. However, this process generates significant by-products and thus can become iaefficient. 

UOP has developed a UOP Sorbex process for the recovery and purification of citric acid from fermentation broths. The process provides technical-grade citric acid, C HgOy, which can be further recrystaUized to obtain food-grade citric acid (qv). 

Certain factors and product precursors are occasionally added to various fermentation media to iacrease product formation rates, the amount of product formed, or the type of product formed. Examples iaclude the addition of cobalt salts ia the vitamin fermentation, and phenylacetic acid and phenoxyacetic acid for the penicillin G (hen ylpenicillin) and penicillin V (phenoxymethylpenicillin) fermentations, respectively. Biotin is often added to the citric acid fermentation to enhance productivity and the addition of P-ionone vastly iacreases beta-carotene fermentation yields. Also, iaducers play an important role ia some enzyme production fermentations, and specific metaboHc inhibitors often block certain enzymatic steps that result in product accumulation. 

Citric Acid. By far the most extensively used food acidulant is citric acid (qv) [77-92-9] C HgO. This acid is favored because of its solubiUty, fresh flavor character, low cost, and low toxicity. It is commercially synthesized by fermentation (qv) of molasses hy Aspergillus niger (6). 

Itaconic 2Lcid[97-65-4] (methylenebutanedioic acid, methylenesuccinic acid) is a crystaUine, high, melting acid (mp = 167-168) produced commercially by fermentation of carbohydrates (1 4). Itaconic acid is produced in the broth from citric acid (qv). Isolated from the pyrolysis products of citric acid in 1836, this a-substituted acryUc acid received its name by rearrangement of aconitic, the acid from which it is formed by decarboxylation. 

Fermentation Feedstock. Sucrose, in the form of beet or cane molasses, is a fermentation feedstock for production of a variety of organic compounds, including lactic, glutamic, and citric acids, glycerol, and some antibiotics. Lesser amounts of itaconic, aconitic, and kojic acids, as well as acetone and butanol, are also produced (41,51—53). Rum is made by fermentation of cane molasses. Beet and cane molasses are used for production of baker s and brewer s yeast (qv). 

Molasses is also used as an inexpensive source of carbohydrate in various fermentations for the production lactic acid, citric acid, monosodium glutamate, lysine, and yeast (60). Blackstrap molasses is used for the production of mm and other distilled spirits. 

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

Physiological Role of Citric Acid. Citric acid occurs ia the terminal oxidative metabolic system of virtually all organisms. This oxidative metabohc system (Fig. 2), variously called the Krebs cycle (for its discoverer, H. A. Krebs), the tricarboxyUc acid cycle, or the citric acid cycle, is a metaboHc cycle involving the conversion of carbohydrates, fats, or proteins to carbon dioxide and water. This cycle releases energy necessary for an organism s growth, movement, luminescence, chemosynthesis, and reproduction. The cycle also provides the carbon-containing materials from which cells synthesize amino acids and fats. Many yeasts, molds, and bacteria conduct the citric acid cycle, and can be selected for thek abiUty to maximize citric acid production in the process. This is the basis for the efficient commercial fermentation processes used today to produce citric acid. 

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. 

Fermentation. The microbial production of citric acid on a commercial scale was begun in 1923 utilizing certain strains yispergillus nigerio produce citric acid on the surface of a sucrose and salt solution. This tray fermentation technique is still used today, although it is being replaced by a submerged process known as deep tank fermentation (14—22). 

Recovery. Citric acid fermentation broth is generally separated from the biomass using filtration or centrifugation. The citric acid is usually... 

Lime-Sulfuric. Recovery of citric acid by calcium salt precipitation is shown in Figure 3. Although the chemistry is straightforward, the engineering principles, separation techniques, and unit operations employed result in a complex commercial process. The fermentation broth, which has been separated from the insoluble biomass, is treated with a calcium hydroxide (lime) slurry to precipitate calcium citrate. After sufficient reaction time, the calcium citrate slurry is filtered and the filter cake washed free of soluble impurities. The clean calcium citrate cake is reslurried and acidified with sulfuric acid, converting the calcium citrate to soluble citric acid and insoluble calcium sulfate. Both the calcium citrate and calcium sulfate reactions are generally performed in agitated reaction vessels made of 316 stainless steel and filtered on commercially available filtration equipment. 

Citric Acid Production in Solid State Fermentation... 

Figure 9.10 shows the flow diagram for production of citric acid in solid-state fermentation. The basis of calculation is 1500 kg citric acid. 

Fig. 9.10. Flow sheet for citric acid in solid-state fermentation.

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... 

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