MASS-TRANSFER STUDIES IN BATCH FERMENTATION - MIXING CHARACTERISTICS

Studies have been undertaken to investigate the mass transfer paramete rs due to mixing effects during fermentation using Candida utilis in a 2.0-dm3 batch fermentor. Mechanical agitation and mixing via air flow have been studied and each varied independently of the other. Oxygen transfer rates were found to increase up to a limiting value when both airflow rate and agitation were increased. Aerobic fermentation is ch aracterised by the specific oxygen rate which increased with agitation and airflow rate. It was found, however, that agitation and aeration had no effect on the carbon dioxide production rate but the mass trans fer coefficient increased markedly with increasing agitation. Values f or all the mass transfer terms were determined. The mass transfer coef ficient, k(L)a, has been correlated with the impeller agitation speed, N, as follows: k(L)a = 1.079 x 10(-3) N1.96.