Vitamin C is also known as L-Ascorbic Acid, which is an essential vitamin for the human body. It is clinically used to treat a variety of diseases, or for preventive medicines and nutritional drugs. Vitamin C is also a strong reducing agent, so it serves as an antioxidant and nutritional additive in the food industry. What's more, Vitamin C plays a certain role in maintaining human blood lipid metabolism, myocardial function and central nervous system activity. The pure product of vitamin C is white crystal or crystalline powder, odorless with sour taste, and its color will gradually become yellowish after a long time. Vitamins are known as a type of organic substances necessary to maintain the life activities of animals, and they are also important active substances for maintaining the health of the body. At present, China is the major producer and exporter of vitamin C, with a total production capacity of more than 120,000 tons, accounting for about 80% of the world market share, which is also one of the most influential products in China's export of APIs.
There are two fermentation processes for the production of vitamin C: the reichstein process and the two-step fermentation method. The above two traditional vitamin C extraction processes adopt the heating precipitation method to remove impurities in the fermentation broth, that is, after the static settlement of the fermentation broth, separate them through cation exchange resin. However, the fermentation broth can directly pass the ion exchange resin, which will cause serious pollution on the surface of the resin, reduce the exchange capacity, consume a lot of energy when heating, and cause some nutrient loss, and the amount of waste water produced is also very large.
Membrane separation technology is an emerging high-efficiency and pollution-free separation technology, which is widely used in chemical, medical, food and other fields because of its non-phase change, low energy consumption, simple device, simple operation, and easy automatic control. In addition, the membrane separation process can be carried out at room temperature, which is suitable for the separation and concentration of heat-sensitive substances, and has great advantages in the separation of biologically active substances.
Modern membrane separation and extraction processes generally use ultrafiltration membranes for the filtration and production of gulonic acid fermentation broth. Because the molecular weight of the protein in the fermentation broth is generally 1-10kDa, the ultrafiltration membrane with a certain molecular weight cut-off can remove most of the protein and some macromolecular impurities so as to replace the traditional heating method to remove protein. The gulonic acid fermentation broth adopts membrane filtration process, which has obvious advantages compared with traditional process: simple process, fully automatic operation, good stability, which improves the yield to reach more than 99% generally in the stage of membrane filtration and impurity removal. The existing membrane filtration processes of vitamin C manufacturers mainly use organic ultrafiltration membranes. Organic ultrafiltration membranes have a relatively high separation accuracy, which can be verified from the protein removal rate of the fermentation broth.
Membrane separation process is combined: Fermentation broth—ultrafiltration—resin desalination—concentrated crystallization—2-keto-L-gulonic acid
(1) Simple process
(2) Save energy and increase yield, and its general yield can reach 99%
This technology adopts ultrafiltration to remove residual mycelium, protein, suspended particles and other impurities in the fermentation broth in one step, and omit pretreatment, heating, centrifugation and other processes, which saves energy consumption and improves the yield of gulonic acid. Since ultrafiltration is a physical process, it will not cause the decomposition or change of 2-keto-L-gulonic acid. The yield mainly depends on the amount of 2-keto-L-gulonic acid in the filter residue, while the filter residue of ultrafiltration contains a small amount of 2-keto-L-gulonic acid, which can be washed by adding water, so the ultrafiltration yield can reach 99%.
Many vitamins can be produced by microbial fermentation, such as vitamin C, vitamin B, and vitamin D. Microbial fermentation to prepare vitamins greatly expands the output of vitamins. Therefore, the application of membrane separation technology in the vitamin fermentation industry has brought huge technical value and economic benefits.