Gas–Liquid and Liquid–Liquid Mass Transfers in Simulated and Actual High Cell Density Fermentations

Abstract

Mass transfer in microbial fermentation affects growth and product formation. Adequate mass transfer is particularly important in high cell density fermentation (HCDF). Gas–liquid and liquid–liquid mass transfers were investigated in high cell density aerobic fermentation of Candida rugosa with palm oil as a sole carbon and energy source. Established correlations were used to predict volumetric mass transfer of palm oil and oxygen in simulated and actual HCDFs, respectively. For liquid–liquid system, a good agreement was found between specific area a determined from oil droplet diameter measurement and theoretical consideration. Consequently, this allowed for reliable determination of k_La in this system. In gas–liquid mass transfer, somewhat larger range of variation was observed between k_La value obtained from theoretical determination and actual measurement. The differences highlighted an important gap in the understanding of complex gas–liquid dynamics of the highly useful HCDF system. The use of established correlations in actual HCDF highlighted both their utility and limitation.

Keywords:

• Agitation rate
• Gas–liquid mass transfer
• High cell density fermentation
• k_la
• Liquid–liquid mass transfer