Characterization of a soybean oil-based biosurfactant and evaluation of its ability to form microbubbles

This paper characterizes the physico-chemical properties of the soybean oil-based polymeric surfactant, Palozengs R-004 (hereafter referred to as R-004). The surface activity of R-004 is comparable to the reported activities of biosurfactants produced by microorganisms and higher than some of the conventional synthetic surfactants. The surface tension of Milli-Q water was reduced to a minimum value of roughly 30 mN/m at a concentration of about 0.07 wt.%. R-004 exhibited a unique aggregation behavior: small aggregates (pre-micelles) were formed at very low concentrations. Zeta-potential measurements showed that the micelles of R-004 are negatively charged due to the presence of carboxylic groups. The ability of R-004 to form and stabilize microbubbles was evaluated and was found to be greatly affected by filtration while remaining independent of R-004 concentration over the concentration range studied (0.05–0.5 wt.%). These results suggest that a very low level of surfactant can be used to produce microbubbles without affecting their properties. Our results suggest the possibility of using soybean oil-based surfactants to food, pharmaceutical, and cosmetic applications.