RESUMO
The fermentation of the high-viscosity polysaccharide WL gum has always been associated with poor mass transfer. Appropriate impeller configurations are key factors in maintaining homogeneity and sufficient mass transfer conditions. Therefore, a flat-folded disc turbine impeller (FFDT) taking into account both the reduced cavitation effect and the increased contact area was designed. Besides, a curved cross impeller (CC) and a fishbone-shaped impeller (FS) generating axial flow were also designed. The energy consumption and efficiency of the designed impellers and eight reported impellers were evaluated through fermentation and principal component analysis (PCA). Compared to the commonly-used six-blade flat-blade disc turbine (FBDT), the ungassed power number of FFDT was reduced by 50 %. Combinations of six-blade Brumajin impeller (BM) + FFDT and CC + FFDT produced high WL gum production and viscosity (34.0 g/L, 35.50 g/L, and 62.64 Pa·s, 61.68 Pa·s, respectively) and were suitable impellers for WL biosynthesis. WL gum from BM + FFDT showed higher viscosity, viscoelasticity, and molecular weight than that from FBDT + FBDT. In addition, fewer amino acids and pyruvic acid intermediates were formed using BM + FFDT, indicating a greater metabolic flux towards WL gum synthesis. This work provided an important reference for the design of impellers in high-viscosity fermentation systems.
RESUMO
BACKGROUND: The molecular chaperone function of αB-crystallins is heavily involved in maintaining lens transparency and the development of cataracts. OBJECTIVES: The aim of the study was to investigate whether divalent metal ion binding improves the stability and αB-crystallin chaperone activity. METHODS: In this study, we have developed an H101G αB-crystallin mutant and compared the surface hydrophobicity, chaperone activity, and secondary and tertiary structure with the wild type in the presence and absence of metal ions. RESULTS: Substitution of His101 with glycine resulted in structural and functional changes. Spectral analysis and chaperone-like activity assays showed that substitution of glycine resulted in a higher percentage of random coils, increased hydrophobicity, and 22±2% higher chaperone-like activity. Whereas in the presence of the Cu2+ ion, H101G exhibited 32±1% less chaperone-like activity compared to the wild type. CONCLUSION: Cu2+ has been reported to enhance the chaperone-like activity of lens α-crystallin. Our results indicate that H101 is the predominant Cu2+ binding site, and the mutation resulted in a partial unfolding that impaired the binding of Cu2+ to H101 residue. In conclusion, this study further helps to understand the important binding site for Cu2+ to αB-crystallin.
Assuntos
Cristalinas , Animais , Dicroísmo Circular , Cristalinas/genética , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Mutação , Dobramento de Proteína , RatosRESUMO
In order to investigate the uptake of lead by rice plant and the distribution of lead in different parts of rice, pot experiment was conducted with 20 rice cultivars of different genotypes by adding lead to soil. The results showed that there existed significant differences among the cultivars in the lead uptake and distribution by rice plants, but the differences had no obvious relationship with rice genotypes. The lead concentrations decreased rapidly from roots to grains along rice plants, so the concentrations of lead were very low in grains compared with other parts of rice plants. The regression analysis showed that there were significant negative correlations between adjacent organs of rice plant, but positive correlations, mostly significant, between disconnected organs, for the lead concentrations in them. Lead concentration in the leaf of heading stage showed a significant positive correlation with that in the grain of ripening stage. Lead was not distributed uniformly in different parts of grain structure, and the lead accumulation in polished rice was only 32.88% of the total lead accumulation in grain.
