THE INFLUENCE OF MECHANICAL FORCES ON THE MORPHOLOGY AND PENICILLIN PRODUCTION OF PENICILLIUM-CHRYSOGENUM

The influence of mechanical forces resulting from the rotation of (mul tiple) turbine impellers on the morphology and penicillin production o f Penicillium chrysogenum Panlabs P-1 was investigated in batch fermen tations using semi-defined media. Experiments were carried out at thre e different scales of fermentation, 5 dm3, 100 dm3 and 1000 dm3 workin g volume, with the impeller tip speed ranging from 2.5 to 6.3 m/s. Thr oughout all fermentations, the dissolved oxygen concentration never fe ll below the critical value for maximum penicillin production. Morphol ogical measurements using image analysis showed that the mean main hyp hal length and mean hyphal growth unit increased during the rapid grow th period and then decreased to a relatively constant value dependent on the agitation intensity. The specific rate of penicillin production (q(pen)) and the average main hyphal length during the linear penicil lin production phase were lower at high agitation speed, which promote d more rapid mycelial fragmentation and a higher branching frequency. Comparison of the results from the three scales showed that impeller t ip speed is a poor scale up parameter whereas a term based on mycelial circulation through the zone of high energy dissipation fitted the da ta well.