Improved capsular polysaccharide production by Streptococcus pneumoniae serotype 14 using continuous cultivation

•Continuous culture was compared to batch for pneumococcal polysaccharide production.•Higher values of biomass and polysaccharide were reached with continuous culture.•Continuous culture avoided autolysis, which was observed only in batch.•Continuous culture is a promising procedure for polysaccharide production.

The capsular polysaccharide (PS) is the most important pneumococcal virulence factor and is currently used as antigen in all pneumococcal vaccines. Despite its physiological and epidemiological importance, meager studies have been devoted to improve PS production and understand its relationship with pneumococcal central metabolism. In this study, kinetics of growth and production of PS by Streptococcus pneumoniae serotype 14 (PS14) in batch and continuous cultivation were investigated. Strong cell lysis was observed in batch cultivation, while accumulation of organic acids and autolysis was avoided in continuous cultivation. In the continuous cultivation was possible to achieve higher concentration of biomass and PS14. Calculation of kinetic parameters demonstrated that PS14 is a cell-associated product. The coefficients for growth-associated stoichiometric true yield and maintenance were determined as 0.25 gglucose gbiomass−1 and 1.24 gglucose (gbiomass h)−1, respectively. The maximum productivity of PS14 released in the supernatant (PS14R) and cell-bound PS14 (PS14C) were obtained at a dilution rate of 0.8 h−1, respectively, 85 and 122 mg  (gbiomass h)−1. Compared to batch fermentation, both PS14R and PS14C productivities were increased by about 300% in the continuous process. These findings demonstrate that continuous cultivation is a promising strategy for PS production to be used in pneumococcal vaccines.

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