Storage and delivery of aquatic microorganisms in emulsions stabilized by surface-modified silica nanoparticles

AGRO 113

Jean S. VanderGheynst, jsvander@ucdavis.edu, Herbert B. Scher, and Hongyun Guo. Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616
Augmentation of microorganisms in aquatic ecosystems is a common approach for the control of insects and weeds and for production of bioenergy. Hydrophobicly-treated silica nanoparticles were investigated for stabilizing microorganisms in water-in-oil (invert) emulsions and for delivery to aqueous environments. Microorganisms studied included the biolarvacide Lagenidium giganteum and a Chlorella sp. Surface treatment of silica nanoparticles had a significant effect on cell death rate; as the hydrophobicity of the silica increased, the rate of death increased. Varying the content of moderately-hydrophobic silica had no effect on cell density measured in the emulsion at time zero, however, increasing the concentration of silica significantly reduced cell death rate, particularly in formulations with a high initial cell density. Microorganisms formulated in emulsions containing silica nanoparticles were less likely to settle when applied to water compared to cells formulated in aqueous suspensions. This suggests that controlled cell distribution and release could be achieved when modified nanoparticles are a component of the emulsion.