Strain Selection and Statistical Optimization of Culture Conditions for 19F Polysaccharide Production from Pneumococcus

Introduction: Capsular polysaccharides of pneumococci are principle antigenic constituents of vaccines against pneumococci. Enhancing the yield of capsule production decreases costs of these vaccines and increases the vaccine coverage in developing countries. This study aims to optimize the capsule production from serotype 19F pneumococcus in terms of the applied pneumococcal strain and environmental culture conditions. Materials and Methods: Thirteen serotype 19F Streptococcus pneumoniae strains were screened for the capsule production in modified Hoeprich culture medium using the stains all assay. The optimal ranges of environmental culture conditions for the selected strain were determined using single factor at a time (SFAT) strategy and utilized for the design of experiments based on the response surface methodology (RSM). Results: S. pneumoniae 82218 showed the highest capsule production, and thus used for further studies. The maximum capsule production (1.364 mg/ml) was attained under optimal conditions (pH 7.26, 35.5 ºC, 30 rpm) predicted by the RSM derived quadratic model. The capsule production under the optimal conditions increased to 1.9 mg/ml using the buffered culture medium. Conclusion: These results are much higher than those reported for pneumococcal capsule production in published studies [1, 2] and thus can be used to design suitable systems for the serotype 19F capsule production in the vaccine manufacturing process.