Vitamin B12 is a water-soluble vitamin produced by bacteria and archaea that is essential for normal functioning of the brain, nervous system, and formation of red blood cells. It is found naturally in animal products like meat, fish, eggs, and dairy. The document outlines the history and industrial production process of vitamin B12 through fermentation using bacteria like Propionibacterium and Pseudomonas, which can produce yields over 60 mg/liter. The production involves formulating nutrient media, sterilization, inoculation with starter cultures, anaerobic and aerobic fermentation steps, and recovery of the cyanocobalamin end product.