RESUMEN

In the present work, the production of bioemulsifier (BE) by a lactic acid bacterium (LAB) grown at 25 °C in lactic whey-based media for 24 h was evaluated. Maximum production was detected in a medium containing yeast extract, peptone and lactic whey (LAPLW medium), with a yield of 270 mg L-1. The BE proved to be more innocuous for Caco-2 cells, used as a toxicological indicator, than the non-ionic surfactant Triton X-100. In addition, the microbial product presented higher stability to changes in temperature (37 °C to 100 °C), pH (2-10), and salt concentration (5% and 20%, w/v) than the synthetic surfactant. Regarding emulsifying capacity tested against different hydrophobic substrates (kerosene, motor oil, diesel, sunflower oil, and grape oil), the BE displayed E24 values similar to or even better than those of Triton X-100. Finally, Triton X-100 caused irreversible modifications on the giant unilamellar vesicles (used as model membrane system), promoting the solubilization of the lipid bilayers. Nevertheless, BE induced temporary modifications of the membrane, which is associated with incorporation of the bioproduct in the outer layer. These results demonstrate the role of BE in biological processes, including reversible changes in microbial membranes to enhance the access to hydrophobic substrates.

Asunto(s)

Biotecnología/métodos , Emulsionantes/aislamiento & purificación , Enterococcus/metabolismo , Ácido Láctico/metabolismo , Suero Lácteo/metabolismo , Células CACO-2 , Supervivencia Celular/efectos de los fármacos , Emulsionantes/metabolismo , Emulsionantes/toxicidad , Emulsiones , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Octoxinol/química , Petróleo/metabolismo , Aceites de Plantas/metabolismo , Temperatura

RESUMEN

A previously reported bacterial bioemulsifier, here termed microbactan, was further analyzed to characterize its lipid component, molecular weight, ionic character and toxicity, along with its bioemulsifying potential for hydrophobic substrates at a range of temperatures, salinities and pH values. Analyses showed that microbactan is a high molecular weight (700 kDa), non-ionic molecule. Gas chromatography of the lipid fraction revealed the presence of palmitic, stearic, and oleic acids; thus microbactan may be considered a glycolipoprotein. Microbactan emulsified aromatic hydrocarbons and oils to various extents; the highest emulsification index was recorded against motor oil (96%). The stability of the microbactan-motor oil emulsion model reached its highest level (94%) at 50 °C, pH 10 and 3.5% NaCl content. It was not toxic to Artemia salina nauplii. Microbactan is, therefore, a non-toxic and non-ionic bioemulsifier of high molecular weight with affinity for a range of oily substrates. Comparative phylogenetic assessment of the 16S rDNA gene of Microbacterium sp. MC3B-10 with genes derived from other marine Microbacterium species suggested that this genus is well represented in coastal zones. The chemical nature and stability of the bioemulsifier suggest its potential application in bioremediation of marine environments and in cosmetics.

Asunto(s)

Actinomycetales/metabolismo , Emulsionantes/metabolismo , Actinomycetales/clasificación , Animales , Artemia/efectos de los fármacos , Biodegradación Ambiental , Emulsionantes/química , Emulsionantes/toxicidad , Hidrocarburos Aromáticos/química , Concentración de Iones de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Aceites/química , Ácido Oléico/química , Ácido Palmítico/química , Filogenia , Ácidos Esteáricos/química , Temperatura