CHARACTERIZATION AND PROPERTIES OF A MICROBIAL EMULSIFIER PRODUCED FROM CRUDE GLYCEROL

COLIN VERONICA; ALVAREZ ANALÍA; FUENTES, M. SOLEDAD; RULLI, MACARENA; DEL GOBBO LUCIANA

Tucuman

Congreso; Congreso Argentino de Microbiología General SAMIGE; 2017

Bioemulsifiers (BE) are amphipathic molecules used in the bioremediation field due to the role inemulsification, solubilization, and removal of hydrophobic compounds from the environment. Theability of a spore-forming bacterium to produced BE using crude glycerol as a cheap feedstock waspreviously detected. In the current study, partially purified BE was characterized. The ability of themicrobial product and of two commercial synthetic agents such as sodium dodecyl sulfate (SDS) andTriton X-100 (TX-100) to emulsify hydrophobic substrates was also comparatively evaluated.Culture supernatant containing BE was filtered through a dialysis tubing cellulose membrane (Typicalmolecular weight cut-off = 14,000 Da). The concentrate obtained was then used as BE source, andsubjected to hydrolytic treatments with proteinase K (30 U mg−1at 37 °C for 4 h), commercial lipasefrom Candida rugosa(100 U mg−1at 37 °C for 1 h), and acid hydrolysis (10% HCl at 100 °C for 10min) in order to estimate the role of peptides, lipids and sugars on the BE nature. The biodegradabilityof BE, SDS and TX-100 was assayed using the BOD/COD ratio, with BOD and COD as the biologicaland chemical oxygen demand, respectively. BOD and COD parameters were determined according tothe Standard Methods for the Examination of Water and Wastewater. Finally, it was evaluated theemulsifying ability of the three agents on hydrophobic substrates (kerosene, toluene, chloroform,chlordane pesticide and vegetable oils), determining the emulsification index for each substrate afterbeing left to settle for 24 h (E24). All hydrolytic treatments significantly reduced the BE activity on the kerosene, suggesting thatmicrobial product could have a protein fraction as well as sugar and lipid fractions. On the other hand,a virtually negligible BOD/COD ratio was detected for SDS and TX-100 (0.070−0.172), confirming theextremely low biodegradability of these synthetic products. However, BOD/COD ratio was significantlyincreased for BE (0.386) confirming so its biodegradable character. Finally, a differential performanceof the BE, SDS, and TX-100 to emulsify the hydrophobic compounds was detected: a similarperformance of the three agents to emulsify substrates as kerosene and toluene were detected, with E24-values of 61% and 62%, respectively. However, chloroform was only effectively emulsified by theBE, with an E24-value increased 4-fold compared to those detected for the synthetic agents. WhileSDS had poor ability to emulsify a pesticide such as chlordane (E24= 18%), the BE and TX-100 wereoptimal emulsifying agents for this substrate, with similar E24-values between them (61%). Finally,only the BE was able to emulsify vegetable oils as sunflower, canola, and grape, with E24-values thatranged from 38% to 51%. These results could encourage the application of a biodegradable microbialproduct to achieve the effective removal of hydrophobic pollutants, without detriment to the environment.