The industrial production of citric acid adopts the fermentation method. After citric acid is produced by fermentation, the fermentation broth also contains residual sugars, proteins, pigments, colloids, inorganic salts and various impurities in the raw materials. Therefore, to obtain citric acid products that meet the requirements of high-quality standards, one must be taken. A series of physical and chemical methods are used for purification. At present, most of the purification processes used in the industry are calcium salt precipitation. The process is complicated, the production cost is high, and a large amount of waste residue is generated, which seriously pollutes the environment, which has become the main factor hindering the further development of the citric acid industry. The main technology of ion exchange and chromatographic separation in my country's fermentation industry

To be used for impurity removal and refining in the later stage of the production process, and only play an auxiliary role in the entire production process. With the development of chromatographic technology, many applied researches have focused on extracting product components directly from the fermentation broth to simplify the production process, reduce costs, and reduce pollution. For example, people have studied many exchange adsorption separation processes in the production of citric acid. Zhang Hongxun et al. proposed to use anion exchange resin to directly adsorb citric acid from the fermentation broth, eluting with ammonia water to form ammonium citrate, and then transform it into cation exchange resin adsorption. The production process of citric acid, the yield of citric acid can reach more than 93% 1]. Gao Nianfa et al. proposed the use of a weakly basic anion absorbent resin with large absorption capacity and strong anti-pollution performance for alkaline desorption. At the same time, by changing the pressure in the absorption column, the resin is shaken to save the absorption and separation process of the "regeneration" process 2J. After adopting a single anion exchange resin to adsorb citric acid, Qin Tao et al. used hydrochloric acid, nitric acid or sulfuric acid to elute the citric acid, and then regenerated the resin with sodium hydroxide and ammonium hydroxide. The by-product was ammonium salt deep solution. The total yield of citric acid production is greater than 85% 13l. Over the years, we have explored new large-scale continuous chromatography technologies with high separation efficiency, easy scale-up and manufacturing characteristics. Our laboratory is equipped with a simulated moving bed (S) continuous preparative chromatographic separation system composed of 16 columns produced by Knauer in Germany, an HPLC detection device from Anjie Technology, and the design and optimization of the chromatographic separation process In addition, a continuous chromatographic separation device composed of 16 0.5m (1.D.)×5m columns was built for pilot and small-scale production. Through many work carried out in the fermentation of organic acids, amino acids, drugs and starch sugar industries, various new chromatographic production technologies have been developed for the production of different products. In the production of citric acid, the separation and purification of products using chromatographic technology is one of our research topics.