Interactional, functional, and biological properties of lactone sophorolipid (LSL) and collagen oligopeptides (COP)...

For the mixed aqueous solution of LSL and COP, the interaction mode and mechanism have been comprehensively studied using multispectral methods including fluorescence spectrum, ultraviolet-visible (UV-vis )adsorption spectra, and circular dichroism (CD) spectra. The surface activity, particle size, foaming, emulsifying, viscosity, and antibacterial properties were evaluated in detail using a surface tension measurement (ST), dynamic light scattering (DLS), oscillometric method, spectrophotometer, Ubbelohde viscometer, and zone of inhibition separately. Compared with the single LSL or COP aqueous solution, the mixed system shows different performance optimizations in different aspects. The surface activity and foaming properties are mainly attributed to LSL, and the viscosity is attributed to COP. Fluorescence spectroscopy results show using LSL addition that the fluorescence distribution of COP has significant changes and a static quenching mechanism was proved. The results of UV-vis and CD spectra also show the changing conformation of COP using LSL addition. Data on thermodynamic parameters demonstrated that the combination of LSL and COP gives a spontaneous exothermic process and is an enthalpy-driven process. The interaction mechanism between LSL and COP is very helpful for the application and development of the mixed mild biosurfactant-protein system used in the cosmetic and food industries.