Characterization of the emulsifying activity of Enterococcus mundtii 278 culture supernatant: studies of stability and toxicity

GOMEZ JOHANA STEFI; GIANNI KATIA; DEL GOBBO LUCIANA MELISA; VALLEJO MARISOL; MARGUET EMILIO; PEROTTI NORA INES; COLIN VERÓNICA LETICIA

Congreso; XIII Congreso Argentino de Microbiología General; 2018

Microbial emulsifiers or bioemulsifiers (BEs) are amphipathic molecules able to increase the solubility in water of hydrophobic substrates. Therefore, they are usefully used in environmental remediation technologies to remove these contaminants from the environment. Additionally, BEs are widely used in food technology as formulation ingredients since they promote the formation and stabilization of emulsions, improving the texture, consistency and the half-life of food products. Unlike its counterparts obtained by chemical synthesis, BEs are highly stable and non-toxic compounds. In previous studies, was reported the production of BE by the bacterium Enterococcus mundtii 278 in a lactic whey-based culture medium. In the current study, BE and two commercial synthetic emulsifying agents (nonionic surfactant Triton X-100 and ionic surfactant SDS) were characterized according to their stability and toxicity. Culture supernatant containing BE was filtered through a cellulose membrane (cut-off = 14,000 Da) and it used as a partially purified product source. Stability studies were conducted by incubating each emulsifying agent at different temperatures (37ºC−100ºC), pH values (2−10) and of NaCl concentration (5%−20%). After the incubation period, residual emulsification index (E24) was determined using kerosene as hydrophobic substrate. Toxicity studies were conducted by determining the percentage of viability of the Caco-2 cell line after being exposed to each emulsifying agent for 3 h at 37°C. The BE retained 100% of its activity residual for all the temperatures, pH values, and salt concentrations tested. Triton X-100 was also a thermo-stable agent. However, SDS was gradually decreasing its residual E24 according to the increase of temperatures. Concerning the effects of the pH, SDS was most stable in the acid pHs (3?6) with residual E24-values among 62%?44%. In opposite, Triton X-100 showed maximum stability at a neutral pH (residual E24 = 62%). SDS and Triton X-100 (to a greater extent) were sensible to the salt presence, losing all its residual activity for a 20% NaCl. Finally, the viability of Caco-2 cells was significantly affected by the emulsifying agents tested, with viability percentage of the 61%, 75%, and 94% for SDS, BE, Triton X-100. In fact, ionic agents such as SDS tend to be more toxic to animal cells than non-ionic agents. The results presented in this study demonstrate that BE is a highly stable product, with an intermediate toxicity between SDS and Triton X-100 for Caco-2 cell line.