Dissolved carbon dioxide effects on growth, nutrient consumption, penicillin synthesis and morphology in batch cultures of Penicillium chrysogenum

Dissolved carbon dioxide is one variable that changes between scales of bioreactor and may thus have a potential influence on the process as scale alters, and especially so in filamentous fungal cultures. The effects of dCO2 on growth and penicillin production by an industrial strain of Penicillium chrysogenum were examined systematically using a steam sterilisable dCO2 probe and a computerized image analysis system. Although low levels of CO2 stimulated growth (increased biomass, lower mean hyphal growth unit (M.H.G.U.) in lag phase) at the expense of antibiotic synthesis, higher levels led to elevated M.H.G.U.'s in the lag phase and were associated with increased clumping and severely reduced penicillin titre. The adverse effects of dCO2 in these cultures were largely mediated by inhibition of growth and substrate uptake in the lag phase, causing morphological changes which might also contribute to reduced penicillin levels.