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Cardoso, Luciana Santos; Araújo, Maria Ilma; Góes, Alfredo M.; Pacífico, Lucila Grossi Gonçalves; Oliveira, Ricardo Riccio; Oliveira, Sérgio C.

doi:10.1186/1475-2859-6-1

Cited by 203 publications

(85 citation statements)

References 16 publications

(20 reference statements)

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“…Although the specific role that Alg44 plays in polymerization remains unclear, Alg44 could play an indirect role. It has been suggested that there is a mutual stability relationship between Alg8 and Alg44 [3]. The findings obtained in our study, which indicate that the expression of alg8 and alg44 was not related to higher alginate MMW (obtained at 500 rpm), could be explained by a mutual stability relationship between Alg8 and Alg44.…”

Section: Resultscontrasting

confidence: 53%

Evaluation of Gene Expression and Alginate Production in Response to Oxygen Transfer in Continuous Culture of Azotobacter vinelandii

et al. 2014

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Alginates are polysaccharides used as food additives and encapsulation agents in biotechnology, and their functional properties depend on its molecular weight. In this study, different steady-states in continuous cultures of A. vinelandii were established to determine the effect of the dilution rate (D) and the agitation rate on alginate production and expression of genes involved in alginate polymerization and depolymerization. Both, the agitation and dilution rates, determined the partitioning of the carbon utilization from sucrose into alginate and CO2 under oxygen-limiting conditions. A low D (0.07 h−1) and 500 rpm resulted in the highest carbon utilization into alginate (25%). Quantitative real-time polymerase chain reaction was used to determine the transcription level of six genes involved in alginate polymerization and depolymerization. In chemostat cultures at 0.07 h−1, the gene expression was affected by changes in the agitation rate. By increasing the agitation rate from 400 to 600 rpm, the algE7 gene expression decreased tenfold, whereas alyA1, algL and alyA2 gene expression increased between 1.5 and 2.8 times under similar conditions evaluated. Chemostat at 0.07 h−1 showed a highest alginate molecular weight (580 kDa) at 500 rpm whereas similar molecular weights (480 kDa) were obtained at 400 and 600 rpm. The highest molecular weight was not explained by changes in the expression of alg8 and alg44 (genes involved in alginate polymerization). Nonetheless, a different expression pattern observed for lyases could explain the highest alginate molecular weight obtained. Overall, the results suggest that the control of alginate molecular weight in A. vinelandii cells growing in continuous mode is determined by a balance between the gene expression of intracellular and extracellular lyases in response to oxygen availability. These findings better our understanding of the biosynthesis of bacterial alginate and help us progress toward obtain tailor-made alginates.

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Section: Resultscontrasting

confidence: 53%

Evaluation of Gene Expression and Alginate Production in Response to Oxygen Transfer in Continuous Culture of Azotobacter vinelandii

et al. 2014

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“…In order to neutralize the potential effects of lipopolysaccharide found in low levels in Schistosoma- recombinant antigens, polymyxin B was added to cell cultures every 12 h according to an established protocol [14]. …”

Section: Methodsologymentioning

confidence: 99%

<b><i>Schistosoma</i></b> Antigens Downmodulate the in vitro Inflammatory Response in Individuals Infected with Human T Cell Lymphotropic Virus Type 1

Lima

Santos

Oliveira

et al. 2013

Neuroimmunomodulation

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Human T cell lymphotropic virus type 1 (HTLV-1) is the causal agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). While the immune response to HTLV-1 infection is polarized to the Th1-type, chronic helminth infections drive the Th2- and T regulatory-type, and are able to downregulate the inflammatory response in some autoimmune diseases. Objective: To evaluate whether Schistosoma spp. antigens alter the in vitro cytokine response in HTLV-1 infection. Methods: The recombinant Schistosoma antigens Sm29 and ShTSP2 (tetraspanin) and PIII, a fraction of the Schistosoma mansoni adult worm antigen were added to peripheral blood mononuclear cell (PBMC) cultures of HTLV-1-infected individuals and the levels of interferon (IFN)-γ and interleukin (IL)-10 in the supernatants were measured using the ELISA sandwich technique. Results: Compared to the levels of cytokine in nonstimulated cultures, the levels of IFN-γ were reduced in 50, 47 and 50% of patients by the presence of Sm29, ShTsp2 and PIII, respectively. The downregulation of IFN-γ production in the presence of Sm29 antigen was observed mainly in subjects who had lower basal levels of this cytokine. The levels of IL-10, however, increased by the addition of the three antigens in the cultures in 74, 62 and 44% of individuals, respectively. In addition, there was a decrease in the ratio of IFN-γ/IL-10 levels in cultures stimulated with Sm29 and ShTSP2 when compared to nonstimulated ones. Conclusions: The Schistosoma spp. antigens used in this study were able to downmodulate IFN-γ production in vitro in HTLV-1 infection. This may be associated with the increased levels of IL-10 induced by the antigens.

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“…High-temperature-active or -stable enzymes are more favorable than mesophilic counterparts, since high temperatures enhance the mass transfer rate, reduce the substrate viscosity, and reduce the risk of contamination (8,9). For example, thermophilic xylanases are applied in bioconversion processes and pulp bleaching, during which a variety of high-temperature treatments are used prior to or simultaneously with enzyme treatment.…”

mentioning

confidence: 99%

Thermostability Improvement of a Streptomyces Xylanase by Introducing Proline and Glutamic Acid Residues

Wang

Luo

Tian

et al. 2014

Appl Environ Microbiol

102

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cProtein engineering is commonly used to improve the robustness of enzymes for activity and stability at high temperatures. In this study, we identified four residues expected to affect the thermostability of Streptomyces sp. strain S9 xylanase XynAS9 through multiple-sequence analysis (MSA) and molecular dynamic simulations (MDS). Site-directed mutagenesis was employed to construct five mutants by replacing these residues with proline or glutamic acid (V81P, G82E, V81P/G82E, D185P/S186E, and V81P/G82E/ D185P/S186E), and the mutant and wild-type enzymes were expressed in Pichia pastoris. Compared to the wild-type XynAS9, all five mutant enzymes showed improved thermal properties. The activity and stability assays, including circular dichroism and differential scanning calorimetry, showed that the mutations at positions 81 and 82 increased the thermal performance more than the mutations at positions 185 and 186. The mutants with combined substitutions (V81P/G82E and V81P/G82E/D185P/ S186E) showed the most pronounced shifts in temperature optima, about 17°C upward, and their half-lives for thermal inactivation at 70°C and melting temperatures were increased by >9 times and approximately 7.0°C, respectively. The mutation combination of V81P and G82E in adjacent positions more than doubled the effect of single mutations. Both mutation regions were at the end of long secondary-structure elements and probably rigidified the local structure. MDS indicated that a long loop region after positions 81 and 82 located at the end of the inner ␤-barrel was prone to unfold. The rigidified main chain and filling of a groove by the mutations on the bottom of the active site canyon may stabilize the mutants and thus improve their thermostability.

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Untitled

Cited by 203 publications

References 16 publications

Evaluation of Gene Expression and Alginate Production in Response to Oxygen Transfer in Continuous Culture of Azotobacter vinelandii

Evaluation of Gene Expression and Alginate Production in Response to Oxygen Transfer in Continuous Culture of Azotobacter vinelandii

<b><i>Schistosoma</i></b> Antigens Downmodulate the in vitro Inflammatory Response in Individuals Infected with Human T Cell Lymphotropic Virus Type 1

Thermostability Improvement of a Streptomyces Xylanase by Introducing Proline and Glutamic Acid Residues

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