In hydrocarbon fermentation, the efficiency of hydrocarbon uptake by cells is one of the keys to the economical production of single-cell protein. This work is concerned with characterization of cultures with two liquid phases for understanding the hydrocarbon uptake process by cells. Batch cultivation of Candida lipolytica was carried out in shaking flasks and in a tower fermentor with motionless mixers. Microscopic observation and cell and hydrocarbon concentration distribution in batch cultivation showed that some cells are attached to the large oil drops and others are free from them. Interfacila tension between oil and water and Sauter mean drop size decreased as cultivation proceeded. On the basis of the experimental results, the process of hydrocarbon uptake by cells is discussed.

Candida lipolytica (strain ATCC 8662) was grown on a simple defined medium with n-hexadecane as the main carbon source under batch fementation conditions. The relative importance of the cells growing in the aqueous phase on the overall kinetics was studied. The effect of interfacial tension, unoccupied interfacial area, and pseudosolubility on the specific growth was also studied. Results are presented and discussed here.

Candida lipolytica was grown continuously on n-hexadecane as the main source of carbon. A transient continuous-culture experiment was also conducted to investigate hydrocarbon-limited growth; the hydrocarbon feed flow rate was stopped for several hours and then resumed at a reduced steady-state flow rate. Interfacial tension, Sauter mean diameter, pseudosolubility, fraction of cells in the aqueous phase, oil-phase volume fraction, and cell concentration were measured to characterize the system. The microorganisms appear to utilize both the submicron drops and the microscopic drops. The effects of interfacial tension, pseudosolubility, and unoccupied interfacial area on the kinetics of hydrocarbon fermentation are discussed here. A conceptual model for hydrocarbon uptake is presented and discussed.

The degree of emulsification, measured as surface area of oil generated, was studied. The effect of interfacial tension, volume fraction of oil, and power per unit volume on the Sauter mean diameter of the oil drops was determined in an airlift system with motionless mixers. A mathematical expression to predict the Sauter mean diameter was developed using regression techniques. From this equation another equation, which will predict the surface area of oil in terms of the same variables, was derived. The effects of water air surface tension and power per unit volume on the gas hold‐up were obtained using similar techniques. The results show that the interfacial tension and the surface tension are important variables when hydrocarbon fermentations are carried out in airlift systems.