en Artificial intelligence Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine The role of Vi-capsular polysaccharide (Vi-CPS) in human immunity against infection caused by Salmonella typhi is well known. The downstream process of purification generally causes depolymerization of Vi-CPS to a nonimmunogenic low molecular weight form. In the present study, a standard strain of Sal. typhi Ty6s was grown under submerge cultural conditions in a pilot-plant scale of 90 Liter fermentor. At the late exponential growth phase, crude polysaccharide wa obtained from fermentation broth by detergent-phenol extraction method and purified by ultracentrifuge differentiation technique. Analytical data reveals that by optimization of fermentation parameters, not only was the yield of production increased from 1.6 mg/L to 4.9 mg/L, but also the polysaccharide retained its native molecular stability and immunogenicity. Therefore, purified Vi-CPS can be regarded as a reliable immunogen to control typhoid fever in man. Salmonella typhi. Vi-CPS, Polysaccharide vaccine. 37 42 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-421&slc_lang=en&sid=1 HOJJAT AHMADI 20031947532846005815 20031947532846005815 Yes From the Department of Bacterial Vaccine. Research and Production Complex, Pasteur Institute of Iran, BAHMAN TABARAlE 20031947532846005816 20031947532846005816 No From the Department of Bacterial Vaccine. Research and Production Complex, Pasteur Institute of Iran, MEHDI NEJATI 20031947532846005817 20031947532846005817 No From the Department of Bacterial Vaccine. Research and Production Complex, Pasteur Institute of Iran, SAEID AL-e AGHA 20031947532846005818 20031947532846005818 No Razi Vaccine and Serum Research Institute. Hesarak, I.R. Iran.