title: Biosurfactant-protein mixtures: Quillaja Bark Saponin at water/air and water/oil interfaces in presence of β-lactoglobulin.
abstract: The adsorption kinetics of mixtures of a biosurfactant Quillaja Bark Saponin (QBS) with a globular protein, β-lactoglobulin (β-LG) at the water/air and water/tetradecane interfaces was investigated by measuring dynamic interfacial tension with axisymmetric drop shape analysis (ADSA) and maximum bubble pressure (MBP) techniques. With bulk concentration of β-LG fixed at 10(-7) M, the most pronounced synergistic effects in the rate of the QBS adsorption at both interfaces were observed at low biosurfactant concentrations (5 × 10(-7)-1 × 10(-5) M). The synergistic effect due to a protein-biosurfactant complex formation is clearly noticeable, yet less pronounced than, e.g., previously studied QBS/lysozyme mixtures. The surface pressures attained at water/oil interface are higher than in the water/air system, although, at high biosurfactant/protein ratios, the presence of β-LG decelerates adsorption of the QBS/β-LG complex onto the water/tetradecane interface. In analogy to mixtures of synthetic surfactants with proteins, the adsorbed layer gets dominated by QBS at higher biosurfactant concentrations, although the presence of β-LG affects the surface pressures attained even at QBS/β-LG ratios as high as 10(4). The synergistic effects are much less noticeable in foamability and emulsion formation/stability, as probed by the modified Bikerman's and dynamic light scattering (DLS) techniques, respectively.
authors.affiliation: Department of Microbioanalytics, Faculty of Chemistry, Warsaw University of Technology , Warsaw, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Piotrowski
authors.forename: Joanna
authors.initials: J
authors.lastname: Lewandowska
authors.forename: Kamil
authors.initials: K
authors.lastname: Wojciechowski
mesh_terms: D000327:Adsorption; D000388:Air; D000473:Alkanes / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D024301:Plant Bark / Q000737:chemistry*; D031990:Quillaja / Q000737:chemistry*; D012503:Saponins / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000473:Alkanes; D007782:Lactoglobulins; D012503:Saponins; D013501:Surface-Active Agents; C024713:n-tetradecane; D014867:Water