The agp gene encoding the ADP-glucose pyrophosphorylase is involved in cyanobacterial glycogen synthesis and glucosylglycerol formation. By in vitro DNA recombination technology, a mutant with partial deletion of agp gene in the cyanobacterium Synechocystis sp. PCC 6803 was constructed. This mutant could not synthesize glycogen or the osmoprotective substance glucosylglycerol. In the mutant cells grown in the medium containing 0.9 M NaCl for 96 h, no glucosylglycerol was detected and the total amount of sucrose was 29 times of that of in wild-type cells. Furthermore, the agp deletion mutant could tolerate up to 0.9 M salt concentration. Our results suggest that sucrose might act as a similar potent osmoprotectant as glucosylglycerol in cyanobacterium Synechocystis sp. PCC 6803.
The agp gene encoding ADP-glucose pyrophosphorylase is involved in cyanobacterial glycogen synthesis. By in vitro DNA recombination technology, agp deletion mutant (agp-) of cyanobacterium Synechocystis sp. PCC 6803 was constructed. This mutation led to a complete absence of glycogen biosynthesis. As compared with WT (wild type), a 60% decrease in ratio of the c-phycocyanine/chlorophyll a and no significant change in the carotenoid/chlorophyll a were observed in agp- cells. The agp- mutant had 38% less photosynthetic capacity when grown in light over 600 micromol m(-2) s(-1). Under lower light intensity, the final biomass of the mutant strain was only 1.1 times of that of the WT strain under mixotrophic condition after 6 d culture. Under higher light intensity, however, the final biomass of the WT strain under mixotrophic conditions was 3 times that of the mutant strain after 6 d culture and 1.5 times under photoautotrophic conditions. The results indicate that there is a minimum requirement for glycogen synthesis for normal growth and development in cyanobacteria.
In this paper, we adopted a simple and efficient strategy to prepare a β-cyclodextrin (β-CD)-modified hyper-crosslinked polymer (CDM-HCP). The structures and physicochemical properties of the as-synthesized polymer were also evaluated. It was applied to the removal of anilines from aqueous solutions. The introduction of β-CD into the hyper-crosslinked polymer significantly enhanced adsorption properties for the removal of various amines. The adsorption kinetics agreed with the pseudo-second-order mode very well. The adsorption isotherm data of p-methylaniline (p-MA) and p-aminobenzoic acid (p-ABC) were in agreement with the Langmuir isotherm, whereas aniline and p-chloroaniline (p-CA) were fitted best with the Freundlich model. The maximum adsorption capacities (qmax) determined by adsorption isotherms were 148.97 mg/g for aniline, 198.45 mg/g for p-MA, 293.71 mg/g for p-CA, and 622.91 mg/g for p-ABC, respectively. It had higher adsorption capacities than those of some commercial polymeric resins, such as XAD-4, PA66, and AB-8. The interaction mechanism was investigated by FTIR, XPS, and the ONIOM2 method. A CDM-HCP can be regenerated efficiently and used repeatedly, indicating its potential technological applications in removing organic pollutants from actual industrial effluents.
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