Effects of sodium bicarbonate concentration on growth, photosynthesis, and carbonic anhydrase activity of macroalgae Gracilariopsis lemaneiformis, Gracilaria vermiculophylla, and Gracilaria chouae (Gracilariales, Rhodophyta).

There is potential for bicarbonate to improve crop yields and economic efficiency of marine algae. However, few studies have focused on the effect of bicarbonate on the growth, photosynthesis, and enzyme activity associated with carbon utilization, especially in commercial macroalgae. Here, the addition of bicarbonate (up to 420 mg L(-1)) to macroalgal cultures has been evaluated for Gracilariopsis lemaneiformis, Gracilaria vermiculophylla, and Gracilaria chouae with respect to growth rate, photosynthetic activity, carbonic anhydrase activity, and biochemical composition. The results showed that the effects of NaHCO3 on growth, chlorophyll a, phycoerythrin, photosynthetic oxygen evolution, photochemical parameters of PSI and PSII, carbonic anhydrase activity, and nitrogen content were significant (P < 0.05) and followed the same pattern in the three species. The parameter values were promoted in lower NaHCO3 concentrations (up to 252 or 336 mg L(-1)) and inhibited in higher NaHCO3 concentrations (>336 mg L(-1) for Gp. lemaneiformis and >420 mg L(-1) for the other two species). Moreover, species-specific differences induced by supplementation with bicarbonate were discovered during culture. Optimal concentrations of NaHCO3 used in this study were 252 mg L(-1) for Gp. lemaneiformis and 336 mg L(-1) for G. vermiculophylla and G. chouae. These results suggest that an adequate supplementation of sodium bicarbonate is a viable strategy for promoting growth and photosynthetic activity in some macroalgae as well as for improving biochemical composition. The study will help to accelerate the growth rate of algae and improve the quality of thalli, and will also be useful for enhancing the understanding of carbon utilization in macroalgae.

Effect of cadmium sulfide quantum dots on physical properties of R-phycoerythrin as a protein matrix.

The synthesis and analysis of nanostructures in the cavities of protein molecules is a promising research field in the industry of nanosystems. In this study, atomic force microscopy (AFM) has been used to evaluate the properties of CdS quantum dots synthesized in the tunnel cavities of R-phycoerythrin, a 290 kDa water-soluble pigment protein responsible for light harvesting in red algae. It has been shown that R-phycoerythrin dissolved in deionized water to a concentration of 50 µg/ml is prone to self-organization into regular spatial structures upon adsorption on the surface of mica, but no such structuring takes place in films prepared from R-phycoerythrin solutions diluted tenfold. In the latter case, protein molecules are deformed, as judged from the analysis of the surface profile. R-phycoerythrin with CdS quantum dots in protein cavities (the concentration of the preparation was (48 µg/ml) loses the self-organization ability and is not deformed upon adsorption on the mica surface. Analysis of AFM images by flicker-noise spectroscopy has shown that incorporation of CdS quantum dots into R-phycoerythrin molecules provides for "smoothing" of the protein surface, with various irregularities being leveled off. Conversely, the irregularity of the protein surface increases when R-phycoerythrin molecules are arranged into three-dimensional branching structures. It is concluded that CdS quantum dots interfere with protein-protein interactions and restrain the conformational mobility of the protein. The anomalously rigid structure of R-phycoerythrin in the presence of CdS is due to its conformational rearrangements during the synthesis of quantum dot.

Sucrose, sodium dodecyl sulfate, urea, and 2-mercaptoethanol affect the thermal inactivation of R-phycoerythrin.

Thermal inactivation kinetics (D- and z-values) of the algal protein, R-phycoerythrin (R-PE), were studied under different buffer conditions (pH 4.0, 7.0, and 10.0) and concentrations of sucrose, sodium dodecyl sulfate (SDS), urea, and 2-mercaptoethanol (ME). R-PE solutions were heated in capillary tubes at temperatures between 40 and 90 degrees C depending on buffer conditions. Thermal inactivation parameters for R-PE, calculated on the basis of fluorescence loss, were modified by addition of chemicals. Overall, sucrose and ME had a thermostabilizing effect, while SDS and urea decreased thermal stability of R-PE. The z-values ranged from 5.9 degrees C in 50 mM NaCl, 20 mM glycine buffer, pH 10.0, to 37.8 degrees C in 60% sucrose, 50 mM NaCl, 20 mM phosphate buffer, pH 7.0. The z-values obtained for R-PE closely matched the z-values of some target microorganisms in food processes, suggesting R-PE might be used as a time-temperature integrator to verify thermal processing adequacy.

Autoxidative and antioxidative potential of simple carbohydrates.

To determine the relative ranking of autoxidative potential of various sugars the fluorescence of phycoerythrin was monitored in the presence of various concentrations of sugars incubated at 37 degrees C with or without CuSO4. The antioxidative properties of these sugars was assayed in the presence of a peroxy radical generator 2,2' azobis(2 amidinopropane) AAPH. The results indicate that 25 mM D-glucose, but not 5 mM D-glucose solution can significantly potentiate CuSO4-induced free radical damage after 32 h of incubation. This weak effect was comparable to that seen with lactose or maltose and was in contrast to the high potency of fructose and ribose in potentiating phycoerythrin damage through oxidation. 2-Deoxyribose had an antioxidant effect in this assay. In the presence of AAPH, 25 mM D-glucose, and to a lesser extent, 5 mM D-glucose, had statistically significant free radical quenching effect (61.5 +/- 0.7% and 44.9 +/- 2.4% inhibition of oxidation, respectively). The corresponding free radical quenching effect expressed as percentage inhibition of oxidation for 5 mM fructose, maltose, lactose, ribose, and deoxyribose and ascorbate were 30.2 +/- 1.9%, 49.1 +/- 1.2%, 53.5 +/- 1.6%, 64.7 +/- 1.8%, 68.8 +/- 1.7%, and 69.5 +/- 1.0%, respectively. It is concluded that autoxidative potential of simple sugars is highly diverse. Whereas some sugars have no oxidative potential, others are potent prooxidants in the presence of Cu++, and some can have antioxidant properties. However, the autoxidative potential of reducing sugars is extremely weak compared with that of the free copper ions. All sugars tested have antioxidant effect in the presence of peroxy radical generator. In this assay, the antioxidant potency of deoxyribose was comparable to that of ascorbate.