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Abstract:Use of natural polysaccharides in medicine and food has wide interest in research. In this study, we extracted and purified some polysaccharides from cactus Opuntia dillenii Haw. (ODP). Some preliminary functions of these products were characterized. Under the optimal purification conditions, the yield of ODP extracted from the 2-4 month-old Opuntia dillenii Haw. (T-ODP) was 30.60% ± 0.40%, higher than that of ODP from the 5-10 month-old materials (O-ODP) (18.97% ± 0.58%). The extracted ODP was purified by DEAE sepharose fast flow anion exchange and Sephacryl S-400 chromatography with four fractions obtained (ODP-Ia, ODP-Ib, ODP-IIa and ODP-IIb). Analysis with UV-vis chromatography indicated that ODP-Ia and ODP-IIa were relatively homogeneous molecules with a molecular weight of 339 kD and 943 kD, respectively. Results of infrared spectroscopy indicated that ODP, ODP-Ia, and ODP-IIa were acidic polysaccharides. Further, the antioxidant activity against DPPH (1,1-diphenyl-2-picrylhydrazyl) radical, hydroxyl radicals, and superoxide radical in vitro demonstrated that the T-ODP exhibited higher antioxidant activity than the O-ODP, and the purified fraction (ODP-Ia) was superior to the ODP. These results will offer a theoretical basis for further research on the structure-function relationship of ODP and the rational utilization of Opuntia dillenii Haw.

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Seedling hypocotyls were used as explants to establish a regeneration protocol for Eucalyptus urophylla and N-phenyl-N'-[6-(2-chlorobenzothiazol)-yl] urea (PBU), one kind of di-substituted urea, was found useful growth regulator. The hypocotyls incubated on a modified Murashige and Skoog medium (SPCa), supplemented with 6.6 μM PBU and 0.57 μM indole-3-acetic acid (IAA) dedifferentiated and form calli (100 % after 7 d). Compared with other growth regulator combinations, PBU stimulated more vigorous calli and restrained their darkening. In addition, the calli induced by PBU showed high frequency of adventitious buds formation (57 %). Shoot proliferation and elongation was then stimulated on SPCa medium containing 0.44 μM 6-benzyladenine (BA), 0.54 μM naphthalene acetic acid (NAA) and 0.3 μM gibberellic acid (GA 3 ). For rooting, shoots were cultivated on root induction medium containing 2.5 μM indole-3-butyric acid (IBA). Plantlets were then successfully transplanted to greenhouse.

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A bacterium Raoultella sp. X1, based on its 16S rRNA gene sequence, was isolated. Characteristics regarding the bacterial morphology, physiology, and genetics were investigated with an electron microscopy and conventional microbiological techniques. Although the isolate grew and degraded dimethoate poorly when the chemical was used as a sole carbon and energy source, it was able to remove up to 75% of dimethoate via co-metabolism. With a response surface methodology, we optimized carbon, nitrogen and phosphorus concentrations of the media for dimethoate degradation. Raoultella sp. X1 has a potential to be a useful organism for dimethoate degradation and a model strain for studying this biological process at the molecular level.

This study examines the preparation, preliminary characterization and antioxidant abilities of Opuntia dillenii Haw polysaccharides-gelatin microspheres (ODP-GMS). ODP-GMS was prepared through W/O emulsion chemicalcrossline method.The result shows that under the optimal conditions which a water/oil (W/O) ratio of 1 to 3.67, 1.06% emulsifier content and 11.47 mg/mL Opuntia dillenii Haw polysaccharides (ODP), the size of the spheroid ODP-GMS was relatively homogeneous and the diameter exhibited a normal distribution curve. The diameter of the microspheres increased by 22.81±0.45% after they were exposed to water for 2 hours. The accumulative release rate of ODP-GMS reached 90%in HCl over 12 hours, while the release rate was 85% in PBS over 24 hours. ODP-GMS had strong scavenging effects on three types of free-radicals (1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radicals, and superoxide radical). These results suggested that gelatin-based microspheres offer excellent potential as carriers for the controlled release of ODP in functional foods or medicine.