[Distribution of surface components in spray-dried powder of binary system of berberine hydrochloride and dextran based on hydrodynamic size].

The present study explored the correlation between the hydrodynamic size(i.e., hydrated particle size) and the surface component distribution of spray-dried powder based on the binary system model of berberine hydrochloride and dextran. A variety of mixture solutions containing substances of different proportions were prepared, and the hydrated particle sizes of the solutions were measured by laser light scattering technique. Then the effects of molecular weight and mixing proportion on the particle size were analyzed. After the solutions were spray-dried, the surface components of spray-dried powder were determined by X-ray photoelectron spectroscopy. The changes of hydrated particle size of the two substances in different solutions were measured with the altered solution environments, and the distribution of surface components after spray-drying was observed. The results of particle size measurement showed that different solution environments would change the hydrodynamic size of substances. Specifically, the particle size of berberine hydrochloride increased with the increase in ionic strength and solution pH, while the particle size of dextran decreased with the increase in ionic strength and increased with the increase in solution pH. The results of surface components of the spray-dried powder indicated that berberine hydrochloride was prone to accumulate on the surface of particles during spray-drying because of its large hydrodynamic size. Therefore, hydrodynamic size is considered an important factor affecting the surface component distribution of spray-dried powder. As revealed by scanning electron microscopy of the particle morphology of spray-dried powder, the particles of berberine hydrochloride spray-dried powder were irregularly elliptic, and the particles of dextran and mixture spray-dried powders were irregularly spherical with the shrunken surface. Finally, the FT4 powder rheometer and DVS instrument were used to determine the stability, adhesion, and hygroscopicity of the powder. The results showed that when berberine hydrochloride was enriched on the surface, the adhesion of the mixture increased and the fluidity became worse, but the hygroscopicity was improved to a certain extent. In addition, as found by hygroscopic kinetic curve fitting of spray-dried powder, the hygroscopic behaviors of all spray-dried powder conformed to the double exponential function.

Specificity of Pseudomonas isolates on healthy and Fusarium head blight-infected spikelets of wheat heads.

The specificity of culturable bacteria on healthy and Fusarium head blight (FHB)-infected spikelets of wheat heads was investigated to find a candidate of biocontrol agents against FHB. The bacterial genus Pseudomonas was commonly isolated from the tissues, and phylogenetic analysis using 16S ribosomal RNA gene sequences of isolates of the genera revealed that particular phylogenetic groups in the genus specifically inhabited either healthy or infected spikelet tissues. The specificity of each group was suggested to be due to differences in the ability to form biofilms and colonize spikelet tissues; isolates originated from healthy spikelets formed biofilms on polyvinyl chloride microplate wells and highly colonized the spikelet tissues. Other bacterial groups obtained from FHB-infected spikelets less formed biofilms and attached with low densities on the spikelet tissues. Their colonization on the tissues, however, was promoted when co-inoculated with the causal pathogenic fungus, Fusarium graminearum, and several isolates were observed to smash the mycelia in vivo. Moreover, based on results of in vitro mycelial growth inhibition activity, the diseased tissue-originated isolates were verified to have a negative effect on the fungal growth. These results suggest that Pseudomonas isolates obtained from infected spikelet tissues were highly associated with the FHB pathogen and have potential as candidates for biological control against FHB.