RESUMO
Serogroup C polysaccharide from Neisseria. meningitidis constitutes the antigen for the vaccine against the disease caused by this bacterium. Aiming at enhancing the final polysaccharide concentration as well as the overall yield factor (polysaccharide/biomass), 20 cultivations were carried out in Frantz medium in a 13 L bioreactor at 35°C, 0.5 atm, 400 rpm and air flowrate of 2 L/min. A series of nine batch experiments was carried out under three different conditions (with control of dissolved oxygen at 10%, with control of pH at 6.5 and without dissolved oxygen and pH controls). Another set of runs consisted of 11 fed-batch cultivations without dissolved oxygen control, varying glucose concentration from less than 1.0-3.0 g/L, four of which performed controlling the pH at 6.5, and four under partial fed-batch conditions. The highest polysaccharide concentration (0.26 g/L) and the overall yield (0.16 g/g), were obtained in batch and partial fed-batch experiments when glucose concentration was maintained below 1.0 g/L. An empirical relation is proposed to relate the specific production rate of polysaccharide to glucose concentration during the stationary growth phase of the fed-batch runs. The obtained polysaccharide satisfies the molecular weight criterion, being a suitable antigen for vaccine production.
