Models of dependence of the quantity of the Streptococcus pneumoniae biomass and his capsular polysaccharide from the composition of the feeding environment

Aim. The development of a semi-synthetic nutrient medium that provides the maximum amount of capsular polysaccharide (CPS). Materials and methods . We used the strain 521 of S. pneumoniae serotype 23F. Cultivation was carried out in test tubes with 10 ml of polysynthetic nutrient medium of a specific composition. The amount of polysaccharide in the samples was determined using rocket immunoelectrophoresis. Building models and comparing the effects of various components was carried out according to the methodology specified in the tutorial. The calculation of the coefficients of the equation and the assessment of the adequacy of the equations themselves was carried out using RStudio version 1.0.153. Results. As a result of a series of experiments, the coefficients of the regression equations were calculated, their significance was evaluated, and models of dependence of biomass production and CPS were constructed depending on the composition of the nutrient medium. To solve the problem, an experiment was carried out according to the Box-Wilson method. The peptone and glucose concentrations were selected as optimized parameters. The step size ΔSi in the increasing gradient direction was calculated based on the coefficients of the regression equation. At the same time, the exact nature of the dependence was determined. The optimal calculated concentrations of peptone and glucose, at which the formation of CPS is maximum, are 32.6 and 12.1 g/l, respectively. In this case, the forecast yield of the polysaccharide is 239 mg/l. Conclusion . Using the method of fractional factorial experiment, models of the dependence of the biomass amount of S. pneumoniae and its capsular polysaccharide on the composition of the nutrient medium were obtained. The optimal concentrations of the components of the medium were found, which make it possible to increase the level of biomass formation by 10% compared to the standard formulas, and the CPS — by 1.5—2 times.