Herbert Benson Scher

Microencapsulation of pesticides by interfacial polymerization utilizing isocyanate or aminoplast chemistry

Interfacial polymerization microcapsulation processes based on isocyanate or aminoplast chemistry, where all wall-forming reactants are placed in the dispersed oil phase are described. Emphasis is placed on mechanism of interfacial reactions, physical nature of the resulting membranes and methods used to vary membrane permeability. n nPesticide microcapsule formulations can be used to reduce mammalian toxicity and extend activity, to control evaporation, to reduce phytotoxicity, to protect pesticide from rapid environmental degradation, to reduce leaching and to reduce pesticide levels in the environment. Examples are provided to demonstrate how pesticide performance characteristics can be altered using this type of formulation.

Water-in-oil emulsions that improve the storage and delivery of the biolarvacide Lagenidium giganteum

Lagenidium giganteum is an effective biological control agent for mosquitoes with limited use due to poor survival and contamination during storage. Invert (water-in-oil) emulsions using crop oils were investigated for formulating L. giganteum mycelium for improved shelf life and delivery. Cells formulated in a water-in-oil (W/O) emulsion were just as effective against larvae as those formulated in aqueous suspension. Cells formulated in the W/O emulsion and cell suspension settled during storage and formed clumps, which significantly reduced the efficacy of formulations. Hydrophobic silica nanoparticles were added to the W/O emulsion formulation for oil thickening. The addition of silica significantly reduced cell sedimentation and improved storage; thickened W/O emulsions with an initial cell density of 3900xa0CFU/mg applied at 0.5xa0mg/cm2 were greater than 95% effective at infecting mosquitoes after 12xa0weeks of storage at room temperature. Cell density reduction during storage was represented using first-order kinetics. Surface treatment of silica nanoparticles and oil refinement both had a significant effect on the first-order rate constant; as the hydrophobicity of the silica increased and level of oil refinement decreased, the rate constant increased. The percentage of water in the W/O emulsion and type of refined crop oil had no significant effect on the first-order rate constant. Cells formulated in the thickened W/O emulsion were less likely to settle when applied to water compared to cells in aqueous suspension, suggesting better cell distribution in an aqueous environment could be achieved when cells are applied in a W/O emulsion.

Delivery of biological performance via micro-encapsulation formulation chemistry†

Lambda-cyhalothrin micro-capsules have been prepared by a novel in situ procedure. Manipulation of the chemistry has led to slow- and fast-release formulations. The latter has a biological performance comparable to commercial lambda-cyhalothrin emulsifiable concentrates, but exhibits a significantly improved toxicological profile over EC, WP and WG formulations. Micro-encapsulation technology satisfies many of the drivers towards the safer use of pesticides.

Microorganism viability influences internal phase droplet size changes during storage in water-in-oil emulsions

Water-in-oil emulsions provide an alternative for long-term stabilization of microorganisms. Maintaining physical stability of the emulsion and cell viability is critical for large-scale application. Water-in-oil (W/O) emulsions were prepared with the biolarvacide Lagenidium giganteum and the green alga Chlorellavulgaris. Physical stability was measured via light scattering measurements of the internal phase droplets and cell viability was measured by plating and enumerating colony forming units. Emulsions were demonstrated to stabilize L. giganteum and C.vulgaris for more than 4xa0months without refrigeration. Introducing nutrients into the internal phase of W/O emulsions without cells had no significant effect on changes in aqueous phase droplet size dynamics. Internal phase droplet size changes that occurred over time were greater in the presence of cells. Increases in droplet size were correlated with cell death indicating measurement of internal phase droplet size changes may be an approach for monitoring declines in cell viability during storage.

Managing the cultivation and processing of microalgae to prolong storage in water-in-oil emulsions.

Producing biofuel from microalgae on a large scale will require high biomass productivity using systems such as high-rate raceway ponds. The vast scale of proposed raceway ponds, spanning 247 to 988 acres per farm, suggests practices currently used in commercial monoculture agricultural systems will need to be adopted for cultivation of algae. In commercial crop production, monoculture is facilitated by a well-established seed production, distribution, and delivery system. Currently, no such system exists for microalgae. The aims of this study were to investigate the application of water-in-oil (W/O) emulsions for the storage of microalgae and the management steps required to prolong cell viability. Water-in-oil emulsions were prepared with Chlorella sorokiniana, C. minutissima, C. vulgaris var. vulgaris, and C. vulgaris to investigate the impacts of cell cultivation medium and cell acclimation prior to emulsification on cell viability during storage. For emulsions prepared with C. sorokiniana, cells that received an acclimation treatment 24xa0h between cell separation from the cultivation medium and emulsification survived over 100xa0days longer than cells that did not receive an acclimation treatment. Emulsions prepared with C. sorokiniana grown in medium containing 29.7xa0mM KNO3, 1.66xa0mM MgSO4u2009·u20097H2O, and 0.85xa0mM FeSO4u2009·u20092H2O had higher levels of viable cells after 100xa0days of storage compared to cells grown in medium containing 9.90xa0mM KNO3 and 0.20xa0mM MgSO4u2009·u20097H2O with no FeSO4u2009·u20092H2O. The results indicate that processing of cells can be managed to increase the stability of microalgae in W/O emulsions.

Room-temperature storage of microalgae in water-in-oil emulsions: influence of solid particle type and concentration in the oil phase

Water-in-oil emulsions containing silica nanoparticles (Aerosil R974) have the potential to stabilize microalgae for long-term storage. Studies were completed to determine if smectite clays could be used as an alternative to Aerosil R974. Emulsions were prepared with Aerosil R974, and hectorite and bentonite clays in the continuous phase and Chlorella sorokiniana was added to the aqueous phase to monitor the effects of solid particles on emulsion stability. Biological stability (cell viability) was determined using cell density measurements, and physical stability was measured from water droplet size distributions obtained by light scattering measurements and by examining phase separation over time. Measurements were also made to determine the effects of particles in the oil phase on emulsion viscosity. Particle concentrations greater than 0.25xa0wt% in the oil phase were required for maintaining physical stability. In emulsions containing 1xa0wt% solid particles and microalgae, biological stability of cells could be sustained for 340xa0days, regardless of particle type. At 1xa0wt% particles in the oil phase, apparent viscosity was 165xa0% greater for samples containing hectorite and bentonite clays compared to samples containing Aerosil R974. The higher viscosity would need to be considered in large-scale production of emulsions for commercial application.