The production of capsular polysaccharide by Neisseria meningitidis serogroup C in Frantz medium cultivations was studied. Influence of process variables such as temperature, pH and agitation speed on the polysaccharide production were investigated by means of a three-factor face-centered central composite design. An optimal set of those process variables values were calculated using response surface methodology, and results showed that optimal values were: temperature equal to 37 degrees C, pH controlled at 7.0 and agitation speed maintained at 1300 rpm, which correspond to a oxygen global mass transfer coefficient (k(L)a) of 36 h(-1). The capsular polysaccharide concentration achieved under these conditions was equal to 155 +/- 4 mg/L. (c) 2006 Elsevier Ltd. All rights reserved.