Mechanism of enhanced oxygen transfer in fermentation using emulsified oxygen‐vectors

Abstract

Limitations of oxygen transfer in fermentation can be solved using auxiliary liquids immiscible in the aqueous phase. The liquids (called oxygen-vectors) used in this study were hydrocarbon (n-dodecane) and perfluorocarbon (forane F66E) in which oxygen is highly soluble (54.9 mg/L in n-dodecane and 118 mg/L in forane F66E at 35 degrees C in contact with air at atmospheric pressure). It has been demonstrated that the use of n-dodecane emulsion in a culture of Aerobacter aerogenes enabled a 3. 5-fold increase of the volumetric oxygen transfer coefficient(k(L)a) calculated on a per-liter aqueous phase basis. The droplet size of the vector played a crucial role in the phenomena. When a static contact between gas bubble and vector droplet was established in water, the vector covered the bubble, in agreement with positive values of the spreading coefficient for these fluids. The determination of the oxygen transfer coefficients (k(L)) in a reactor with a definite interfacial area enabled the main resistance to be located in the boundary layer of the waterside either for a gas-water or a vector-water interface. Because oxygen consumption by weakly hydrophobic cells can only occur in the aqueous phase, the oxygen transfer is achieved according to the following pathway: gas-vector-water-cell. Finally, a mechanism for oxygen transfer within this four-phased system is proposed.

Gas absorption in an agitated gas–liquid–liquid system

“…The second mechanism proposed to describe the mass transfer enhancement is the so-called coalescence}redis-persion mechanism, which is based on direct contact between gas and the dispersed phase by formation of gas}liquid complexes (Rols et al, 1990). The gas absorption rate is then enhanced due to the introduction of this second transfer path.…”

“…This latter concept is e.g. applied in a few biochemical applications (Rols, Condoret, Fonade & Goma, 1990). However, the addition of a second liquid phase can also retard the gas}liquid mass transfer (Yoshida, Yamane & Miyamoto, 1970).…”

Physical absorption of CO2 and propene into toluene/water emulsions

“…Most publications deal with mass-transfer enhancement in gas-liquid systems, though mass-transfer enhancement in liquid-liquid and solid-liquid systems has been described also (Bunton et al, 1976;Sharma, 1982, 1985a). A possibly important application of mass-transfer enhancement by means of emulsions in gas-liquid systems seems to be the oxygenation of the liquid phase in aerobic fermentation or biological wastewater treatment (Rols et al, 1990).…”

Oxygen mass transfer in a biphasic medium: Influence on the biotransformation of methyl ricinoleate into γ-decalactone by the yeast Yarrowia lipolytica

“…The effects of adding a second liquid organic phase on k L a may change, and it was shown that k L a values may increase, decrease, or remain constant, depending on the nature of the organic compound and the operating conditions [2][3][4][5][6][7][8][9][10][11][12][13][14].…”