Interaction between emulsion droplets and Escherichia coli cells

Oil-in-water emulsions (20% n-hexadecane, v/v) were stabilized by dodecyltr imethylammonium bromide CDTAB), Tween 20, or sodium dodecyl sulfate (SIDS). particle size distribution and creaming stability were measured before and after adding Escherichia coli cells to emulsions. Both E, coli strains pro moted droplet flocculation, coalescence, and creaming in DTAB emulsions, al though JM109 cells (surface charge = -35 mV) caused faster creaming than E2 1 cells (surface charge = -5 mV). Addition of bacterial cells to SDS emulsi ons promoted some flocculation and coalescence, but creaming stability was unaffected. Droplet aggregation and accelerated creaming were not observed in emulsions prepared with Tween 20. Surface charges of bacterial cells and emulsion droplets played a key role in emulsion stability.