Erysipelothrix rhusiopathiae, the causative agent of
swine erysipelas, was cultivated in a 5-L stirred and aerated
bioreactor under different dissolved
oxygen tensions (0%, 5%, and 30% of saturation) for evaluation of the influence of
oxygen on cell growth as well as on the production of the main antigenic component of the
vaccine against
erysipelas, a 64-69 kDa
protein (
SpaA). The microorganism presented different growth profiles for different aeration conditions. However, at the end of the batch cultivations, similar cell concentrations were obtained under the studied conditions. In order to maximize biomass titers and
antigen production, the microorganism was cultivated in fed-batch operation mode under aerobic conditions. Under this condition, there was a fivefold increase in biomass production in comparison to the results attained in batch cultivations. To follow up
antigen expression, samples collected during batch cultivations were concentrated and treated with
choline for
antigen extraction.
Antigen expression was then assessed by
sodium dodecyl sulfate polyacrylamide gel electrophoresis and by murine immunization tests. It was observed a direct influence of
oxygen availability upon
antigen expression, which is favored in the presence of
oxygen. Analysis of the samples collected throughout the fed-batch process also revealed that
antigen production is growth associated.