Application and research progress of corn steep liquor in fermentation industry

Corn steep liquer (CSL) is a by-product of corn starch preparation and can be prepared by wet milling. Corn steep liquor contains large amounts of sulfites, peptides, polysaccharides, proteins, and various amino acids, such as arginine, glutamic acid, histidine, phenylalanine, alanine, and beta-phenethylamine. The main uses of corn steep liquor are: used as water-soluble vegetable protein and water-soluble vitamins, compound fertilizer additives, fermentation nitrogen source and fiber feed. Most of the chemical constituents in corn steep liquor are amino acid precursors synthesized by fermentation, accounting for 25% of the dry mass of corn steep liquor. After hydrolysis with hydrochloric acid for 18h, peptides and proteins are hydrolyzed into amino acids, and the content can reach more than 50% of the dry mass. Currently, only a small fraction of corn steep liquor is used for amino acid fermentation. Corn steep liquor is used as organic nitrogen source and supplier of growth factors in amino acid fermentation, and its rich biotin and limiting amino acids have a great influence on the fermentation of various amino acids. As a cheap and efficient nitrogen source for fermentation, increasing the amount of corn steep liquor used in amino acid fermentation to reduce or replace some organic nitrogen sources, such as soybean meal hydrolyzate, yeast powder and hair powder, can improve the value of corn steep liquor and reduce the production cost of amino acids. In the penicillin fermentation medium, the content of corn steep liquor has a great influence on the process parameters such as mycelium, ammonia nitrogen metabolism, sugar metabolism, fermentation cycle and fermentation titer.