Enhancement of the gas-to-water ethene transfer coefficient by a dispersed water-immiscible solvent: effect of the cells

  For a mass-transfer-limited system, it was demonstrated that the volumetric ethene transfer coefficient (k _l a) from gas to water could be enhanced by dispersing adequate amounts of a water-immiscible organic liquid, namely the perfluorocarbon FC40, in the aqueous phase. When 26% (v/v) FC40 was dispersed in a culture of Mycobacterium parafortuitum an enhancement of k _l a, calculated on a total liquid volume basis, of 1.8 times was found. Steady-state experiments in the absence of microorganisms, however, showed a 1.2-fold enhancement of k _l a at 18.5% (v/v) FC40. At all FC40 volume fractions tested, enhancement factors with cells were higher than enhancements without cells; apparently the microorganisms or their excretion products affected the interfacial areas or characteristic phase dimensions. Received: 4 December 1995 / Received revision: 7 June 1996 / Accepted: 10 June 1996