Monday, May 4, 2009
9-73
Stabilization and Delivery of Chlorella vulgaris in Water-in-Oil Emulsions
Herb Scher, Hongyun Guo, Yu-Shen Cheng, and Jean VanderGheynst. Biological and Agricultural Engineering Department, University of California, Davis, One Shields Avenue, Davis, CA 95616
Microalgae have considerable promise as a feedstock for biofuel production. Since most microalgae do not store well in aqueous suspensions or as a dry formulations, storage and delivery technologies are needed to facilitate their production. We developed a water-in-refined corn oil (W/O) emulsion formulation of Chlorella vulgaris that is physically and biologically stable at room temperature for 6 months. The algae reside in the dispersed water droplets. Emulsion physical stability and algal biological stability is realized by utilizing an oil soluble polymeric surfactant and silica nanoparticles with hydrophobic surface treatment. Light scattering measurements made on emulsions show a slight initial coalescence effect but essentially no change in number average particle size over the span of five months. The excellent physical stability of the emulsions may contribute to the biological stability of the system.
Controlled release studies were conducted to determine the effect of concentration of polymeric surfactant in the W/O emulsion on the release of Chorella minutissma upon application to water. As the surfactant concentration in the oil phase was reduced from 3.0 wt% to 0.3 wt%, the percent release of the total cells applied increased from 3.0% to 17%. This result suggests that the rate of coalescence of water droplets within the W/O emulsion and the eventual rupture of the oil film to allow release of algae is governed by the level of surfactant in the oil phase. Therefore the level of surfactant can be used to adjust the release of algae when applied to a water surface.