Typhoid fever is one of the prevalent pandemics across many developing countries caused by Salmonella typhi. Vi capsular polysaccharide obtained from S. typhi has been licensed for use as a vaccine for children aged 2 years and above to prevent typhoid fever. Production and purification of Vi polysaccharide play a vital role in the immunogenicity and cost of vaccines. Four critical parameters, cetrimide concentration (% w/v), sodium acetate concentration (% w/v), alcohol concentration (% w/v), and operational temperature (°C), were optimized by response surface methodology (RSM). Doehlert design matrix, with 22 experimental runs, was used to optimize the selected parameters. All parameters were studied at different levels. With the help of RSM, by optimizing the selected variable conditions, onefold yield increased and the final purified Vi polysaccharide has noncompliance with the World Health Organizations standards.
Key words: Vi capsular polysaccharide, Salmonella typhi, Typhoid vaccine, Doehlert design, Response surface method, O-acetyl content.
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