Double-chain cationic surfactant and n-pentanol: an L3 phase in the rich-water domain?

A ternary system containing water, pentanol and a quaternary cationic surfactant, dioctadecyldimethylammonium bromide (DODAB) was investigated. We present the phase diagram and ESR studies that demonstrate the existence of the well-known L3 or sponge phase in the water-rich domain of the diagram. The remarkable fact is the existence of some kind of order in such diluted conditions.

Cell Culture Derived AgMNPV Bioinsecticide: Biological Constraints and Bioprocess Issues.

We have studied parameters for optimizing the Spodoptera frugiperda (Sf9) cell culture and viral infection for the production of Anticarsia gemmatalis multiple nucleopolyhedrosis virus (AgMNPV) polyhedra inclusion bodies (PIBs) in shaker-Schott or spinner bottles and bioreactors. We have assayed the k(L)a of the systems, initial cell seeding, cell culture volume, dissolved oxygen (DO), multiplicity of infection (MOI), nutrients consumption, and metabolites production. The medium surface oxygen transfer was shown to be higher in shaker bottles than in spinner ones, which was in direct correlation to the higher cell density obtained. Best quantitative performances of PIBs production were obtained with a SF900II medium volume/shaker-bottle volume ratio of 15% and MOI of 0.5 to 1 performed at a cell concentration at infection (CCI) of 1 to 2.5x10(6) cells/ml in a medium containing enough glucose and glutamine. Upon infection, a decrease in the cell multiplication was observed to be dependent on the MOI used, and the muX at the exponential growth phase in infected and non-infected cultures were, respectively, of 0.2832 and 0.3914 (day(-1)). The glucose consumption and lactate production were higher in the infected cultures (muGlucose and muLactate of, respectively, 0.0248 and 0.0089x10(-8) g/cellxday in infected cultures and 0.0151 and 0.0046x10(-8) g/cellxday in non infected ones). The glutamine consumption did not differ in both cultures (muGlutamine of 0.0034 and 0.0037x10(-8) g/cellxday in, respectively, infected and non infected cultures). When a virus MOI of 0.1 to 1 was used for infection, a higher concentration of PIBs/ml was obtained. This was in direct correlation to a higher cell concentration present in these cultures, where a decrease in cell multiplication due to virus infection is minimized. When a MOI of 1 was used, a more effective decrease in cell multiplication was observed and a lower concentration of PIBs/ml was obtained, but with the best performance of PIBs/cell. Correlations between MOI and CCI indicate that a MOI 0.1 to 1.4 and a CCI of 10(6) to 2x10(6) cells/ml led to the best PIBs production performances. The virulence of PIBs produced in cultures infected at low or high MOI showed comparable DL(50). Culture and infection in scaling-up conditions, performed in a bioreactor, were shown to provide the cells with a better environment and be capable of potentially improving the shaker-Schott findings. For an accurate qualitative control of PIB virulence, hemolymph from AgMNPV infected Anticarsia gemmatalis was used as starting material for passages in Sf9 cells. These led to a loss of virulence among the PIBs with an increase in the DL(50). The loss of virulence was accompanied by a loss in budded virus titer, a decreased number of PIBs produced and an altered DNA restriction pattern, suggesting the generation of defective interference particles (DIPs). Transmission electron microscopy (TEM) studies revealed that after cell passages, PIBs lacking virions were progressively synthesized. The study described here point out the biological constraints and bioprocess issues for the preparation of AgMNPV PIBs for biological control.

Heteroflocculation of Sulfate Polystyrene Latex and Anticarsia gemmatalis Nucleopolyhedrovirus as a Model System for Studying Sunlight Protection.

Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus widely used as a pest control agent. Data on field persistence of this microbial insecticide reveal that sunlight is the most destructive of the environmental factors. The introduction of a physical barrier to protect the baculovirus from sunlight has been proposed. In the present work we report on the coating of a baculovirus surface with a uniform layer of smaller particles. The coating was carried out at pH 3, a condition where the baculovirus surface becomes positively charged and can be covered by sulfate polystyrene latex particles. The heteroflocculation was assessed by isotherm measurements and scanning electron microscopy. High-affinity isotherms were obtained for the two sizes of latex used, and the number of latex particles bound per baculovirus was not affected when pH was changed back to neutral range (5

Heteroflocculation of Amidine Polystyrene Latex and Anticarsia gemmatalis Nucleopolyhedrovirus as a Model System for Studying Sunlight Protection.

Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus specific for the control of an important soybean defoliator. The baculovirus is comprised of double-stranded DNA, occluded in a proteinaceous structure called a polyhedron. Ultraviolet sunlight is the most destructive factor that affects the persistence of the virus in the field. In the present study, we use a model system wherein the pathogen is covered by another particle of opposite charge in order to test the effectiveness of a physical barrier as a protection against sunlight. Heteroflocculation experiments were carried out using two different age batches of AgMNPV and amidine polystyrene latex particles. The assessment of heteroflocculation was achieved by zeta potential and adsorption isotherm measurements, and by scanning electron microscopy. Despite the great difference in potentials between latex particles and the baculovirus, low-affinity isotherms were obtained in both pure water and 0.1 mM KCl. Adsorbed latex particles were easily washed out from the polyhedron surface. This low affinity could be attributed to the presence of a strongly repulsive hydration force of short range operating on the system. The results suggest that the failure to obtain a good physical barrier against sunlight might be attributed to the difficulty in keeping the polyhedron surface covered. Copyright 2000 Academic Press.