Dairong Qiao

Sichuan University, Hua-yang, Sichuan, China

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Publications (37)46.85 Total impact

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    ABSTRACT: Agar is a polysaccharide extracted from the cell walls of some macro-algaes. Among the reported agarases, most of them come from marine environment. In order to better understand different sources of agarases, it is important to search new non-marine native ones. In this study, seven agar-degrading bacteria were first isolated from the tissues of plants, belonging to three genera, i.e., Paenibacillus sp., Pseudomonas sp., and Klebsiella sp. Among them, the genus Klebsiella was first reported to have agarolytic ability and the genus Pseudomonas was first isolated from non-marine environment with agarase activity. Besides, seven strains were characterized by investigating the growth and agarase production in the presence of various polysaccharides. The results showed that they could grow on several polysaccharides such as araban, carrageenan, chitin, starch, and xylan. Besides, they could also produce agarase in the presence of different polysaccharides other than agar. Extracellular agarases from seven strains were further analyzed by SDS-PAGE combined with activity staining and estimated to be 75 kDa which has great difference from most reported agarases.
    Current microbiology. 10/2014;
  • Applied Catalysis A General 05/2014; 478:175–185. · 3.41 Impact Factor
  • Shu Zhang, Yu Cao, Li Xie, Dairong Qiao, Yi Cao
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    ABSTRACT: Superoxide dismutases (SOD) are able to remove the superoxide anion free radicals produced by environmental stress and thereby protect cells from being injured by reactive oxygen species. However, SOD is unable to transduce automatically across cell membranes. Protein transduction domains (PTDs) are peptides able to mediate protein delivery into cells and were first observed in the HIV‑1 Tat protein. In the present study, PTD (RKKRRQRRR) was fused to Dunaliella salina (Ds)MnSOD to form PTD‑DsMnSOD. This was inserted into pET32a to construct the recombinant plasmid pET32a‑PTD‑DsMnSOD and transduced into E. coli BL21(DE3) to obtain purified PTD‑DsMnSOD proteins. Liposome‑encapsulated proteins are also able to cross cell membranes. In this study, DsMnSOD proteins were purified and encapsulated by liposomes. The obtained MnSOD, PTD‑MnSOD and liposome MnSOD were used to protect human umbilical vein endothelial cells (HUVECs) from injury under oxygen pressure. A cell counting kit 8 was used to test the survival rate of HUVECs and results indicated that the protective effect of MnSOD was limited compared with that of PTD‑MnSOD and liposome MnSOD. Thus, PTD and liposomes exhibited improved effects when MnSOD was present in cells.
    Molecular Medicine Reports 04/2014; 9(4):1427-33. · 1.17 Impact Factor
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    ABSTRACT: In order to improve the expression of heat-resistant xylanase XYNB from Aspergillus niger SCTCC 400264, XynB has been cloned into Pichia pastoris secretary vector pPIC9K. The XynB production of recombinant P. pastoris was four times as E. coli, the Vmax and specific activity of XynB reached 2547.7μmol/mg and 4757 U/mg, respectively. And the XynB still had 74% residual enzyme activity after 30 minute-heat treatment at 80 °C. The van der Waals force analysis in XYNB (ACN89393 and AAS67299), there is one more oxygen radicals in AAS67299 in their catalytic site, indicating that the local cavity is much more free, and it is more optimal for substrate binding, affinity reaction, and proton transfer etc, and eventually increasing enzyme activity. The H-bonds analysis of XYNB indicated that there are two more H-bonds in 33rd Ser of XYNB ( AAS67299) than 33rd Ala(ACN89393 ), two H-bonds between Ser70 and Asp67.
    Journal of Microbiology and Biotechnology 01/2014; · 1.40 Impact Factor
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    ABSTRACT: Triacylglyceride (TAG) and carbohydrate are potential feedstock for biofuels production. In this study, a two-stage process was applied for enhancing TAG/carbohydrate production in the selected microalgae - Neochloris oleoabundans HK-129. In stage I, effects of nitrogen, light intensity and iron on cell growth were investigated, and the highest biomass productivity of 292.83±5.83mg/L/d was achieved. In stage II, different nitrogen-starvation periods, light intensities and iron concentrations were employed to trigger accumulation of TAG and carbohydrate. The culture under 2-day N-starvation, 200μmol/m(2)/s light intensity and 0.037mM Fe(3+) concentration produced the maximum TAG and carbohydrate productivity of 51.58mg/L/d and 90.70mg/L/d, respectively. Nitrogen starvation period and light intensity had marked effects on TAG/carbohydrate accumulation and fatty acids profile, compared to iron concentration. The microalgal lipid was mainly composed of C16/C18 fatty acids (90.02%), saturated fatty acids (29.82%), and monounsaturated fatty acids (32.67%), which is suitable for biodiesel synthesis.
    Bioresource Technology 01/2014; 155C:204-212. · 5.04 Impact Factor
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    ABSTRACT: Agar is a polysaccharide polymer material, generally extracted from seaweed. Most agar degradation strains were isolated from seawater. In order to find new species resources and novel agarase from soil, an agar-degrading bacterium Paenibacillus sp. SSG-1 was isolated from soil. Agarase SSG-1a was purified to homogeneity by 30.2 fold with a yield of 4.8% through ammonium sulfate precipitation, DEAE FF chromatography and native-PAGE separation. The tandem mass spectrometry (MS/MS) results indicated that purified SSG-1a should be a novel β-agarase. The molecular mass of SSG-1a was estimated to be 77 kDa. The optimal temperature and pH for SSG-1a were 50°C and pH 6.0, respectively. Moreover, SSG-1a was stable in pH range of 4.0–10.0 and at temperature up to 40°C. It could hydrolyze the β-1,4 linkage of agarose to produce neoagarohexaose (95 mol%) and neoagarooctaose (5 mol%). Metal ion Mn2+ and reducing reagents (β-Me and DTT) could increase its activity by 150% and 60%, respectively.
    Journal of Bioscience and Bioengineering 01/2014; · 1.74 Impact Factor
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    ABSTRACT: We collected flies from Chengdu Shuangliu International Airport to examine for the presence of bacteria and to determine the sensitivity patterns of those bacteria. A total of 1,228 flies were collected from 6 sites around Chengdu Shuangliu International Airport from April to September 2011. The predominant species was Chrysomya megacephala (n=276, 22.5%). Antimicrobial-resistant gram-negative enteric bacteria (n=48) were isolated from flies using MacConkey agar supplemented with cephalothin (20 microg/ml). These were identified as Escherichia coli (n=37), Klebsiella pneumoniae (n=6), Pseudomonas aeruginosa (n=3) and Aeromonas hydrophila (n=2). All isolated bacteria were tested for resistance to 21 commonly used antimicrobials: amoxicillin (100%), ticarcillin (100%), cephalothin (100%), cefuroxime (100%), ceftazidime 1 (93.8%), piperacillin (93.8%), cefotaxime (89.6%), ticarcillin-clavulanate (81.3%), trimethoprim-sulfamethoxazole (62.5%), ciprofloxacin (54.2%), gentamicin (45.8%), cefepime (39.6%), tobramycin (39.6%), ceftazidime (22.9%), cefoxitin (16.7%), amikacin (16.7%), netilmicin (14.6%), amoxicillin-clavulanate (6.3%) and piperacillin-tazobactam (2.1%). No resistance to meropenem or imipenem was observed. Antibiotic resistance genes among the isolated bacteria were analyzed for by polymerase chain reaction. Thirty of the 48 bacteria with resistance (62.5%) possessed the blaTEM gene.
    The Southeast Asian journal of tropical medicine and public health 11/2013; 44(6):988-96. · 0.61 Impact Factor
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    ABSTRACT: A general model of the catalytic mechanism for 5-enolpyruvylshikimate-3-phosphate synthase (EPSPs) has already been proposed. But whether shikimate-3-phosphate (S3P) alone can cause EPSPs' conformation changes, and whether the binding site of phosphoenolpyruvate (PEP) and glyphosate is the same are still in debate. In this paper, DsaroA gene amplified and cloned from Dunaliella salina (our laboratory's early study) was used for DsEPSPs expression and purification. Then the DsEPSP conformation changes as it bind with different substrates were detected by fluorimetry. The results show that we obtained the DsEPSPs by prokaryotic expression and purification, and the S3P binding with DsEPSPs alone cannot cause DsEPSPs to form "close" conformation directly. However, when S3P exits, DsEPSPs did have a trend to change to the "close" conformation. Then the "close" conformation can be formed completely with the addition of phosphoenolpyruvate (PEP) or glyphosate. The inorganic phosphorus can help S3P to induce two domains of DsEPSPs to form "close" conformation. Besides, when DsEPSPs binds with S3P, in 295 nm, only the intensity of emission peak decreases, however, in 280 nm, not only the peak intensity reduces but also the blue-shift phenomenon takes place. The reason for blue-shift phenomenon was the distribution of aromatic amino acids in EPSPs. EPSPs is a good target for novel antibiotics and herbicides, because of shikimic acid pathway is only present in plants and microorganisms, completely absent in mammals, fish, birds, reptiles, and insects. The results demonstrate that the binding of substrates to EPSPs causes a conformational change from an open form to a closed form, that might be important for designing of novel antimicrobial and herbicidal agents that block closure of the enzyme.
    Journal of Basic Microbiology 09/2013; · 1.20 Impact Factor
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    ABSTRACT: Dunaliella salina, a unicellular green alga, has the potential to grow in hypersaline environments via one of its gene products, superoxide dismutase (SOD). The superoxide radicals (O2 (-) ) produced by environmental stresses can cause damage to cells, and SOD catalyzes the turnover of such free radicals to protect cells. In this study, the gene coding for SOD in D. salina was cloned and the product was further identified and characterized. The open reading frame of this gene was 651 bp long, encoding for 217 amino acids. According to the sequence alignment using BLAST, native polyacrylamide electrophoresis for SOD activity analysis, and atomic absorption spectroscopy analysis, this protein belongs to the manganese-containing superoxide dismutase (MnSOD) family. Complementation analysis, performed by introducing plasmids carrying an inducible version of the D. salina gene encoding for MnSOD into an SOD-deficient mutant of E.coli, revealed that this gene could not only complement the defects in SOD activity, but was also capable of providing a stronger tolerance to restrictive growth conditions, such as high salt and prolonged UV exposure, compared to the tolerance of wild-type strains.
    Journal of Basic Microbiology 05/2013; · 1.20 Impact Factor
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    ABSTRACT: Despite recent advances in our understanding of the importance of protein surface properties for protein thermostability,there are seldom studies on multi-factors rational design strategy, so a more scientific, simple and effective rational strategy is urgent for protein engineering. Here, we first attempted to use a three-factors rational design strategy combining three common structural features, protein flexibility, protein surface, and salt bridges. Escherichia coli AppA phytase was used as a model enzyme to improve its thermostability. Moreover, the structure and enzyme features of the thermostable mutants designed by our strategy were analyzed roundly. For the single mutants, two (Q206E and Y311K), in five exhibited thermostable property with a higher success rate of prediction (40 %). For the multiple mutants, the themostable sites were combined with another site, I427L, we obtained by directed evolution, Q206E/I427L, Y311K/I427L, and Q206E/Y311K/I427L, all exhibited thermostable property. The Y311K/I427L doubled thermostability (61.7 %, and was compared to 30.97 % after being heated at 80 °C for 10 min) and catalytic efficiency (4.46 was compared to 2.37) improved more than the wild-type AppA phytase almost without hampering catalytic activity. These multi-factors of rational design strategy can be applied practically as a thermostabilization strategy instead of the conventional single-factor approach.
    Journal of Industrial Microbiology 03/2013; · 1.80 Impact Factor
  • Yuzhi Miao, Hui Xu, Baojin Fei, Dairong Qiao, Yi Cao
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    ABSTRACT: The major objective of this study was to engineer lactic acid bacteria to produce the enzyme phytase from a gene native to Bacillus subtilis GYPB04. The phytase gene (phyC) of B. subtilis GYPB04 was cloned into the plasmid pMG36e for expression in Lactococcus lactis. The enzyme activity in L. lactis cultured in GM17 broth was 20.25 U/mL at 36°C. The expressed phytase was characterized as active in a pH range of 2.0-9.0 at a temperature range of 20-80°C, with an optimum pH of 5.5-6.5 and temperature of 60°C. When cultured in food-grade milk broth, the transformed L. lactis grew to an OD600 nm value of 1.05 and had a phytase yield of 13.58 U/mL. In same broth under optimized conditions for cell growth and phytase production, the transformant reached an OD600 nm value of 1.68 and a phytase yield of 42.12 U/mL, representing approximately 1.6-fold and 3.1-fold increases, respectively, compared to growth in natural milk broth. Fermentation was scaled to 5 L under optimized conditions, and product analysis revealed a final OD600 nm value of 1.89 and an extracellular enzyme activity of 24.23 U/mL. The results of this study may be used in the dairy fermentation industry for the development of functional, healthy yogurts and other fermented dairy foods that provide both active phytase and viable probiotics to the consumer.
    Journal of Bioscience and Bioengineering 02/2013; · 1.74 Impact Factor
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    ABSTRACT: In order to study on the relationship between Escherichia coli AppA phytase's thermostability and salt bridges, and indicate an effective technical route of which factor to think about and where to modify at AppA for enhancing its thermostability, a salt bridge subtraction mutant E31Q and a salt bridge addition mutant Q307D were constructed by site-directed mutagenesis. The residual activities of the wild-type AppA phytase, E31Q and Q307D were 31.42%, 17.46%, and 40.57%, respectively, after being heated at 80°C for 10 min. The salt bridge subtraction mutant E31Q showed 13.96% thermostability decreasement, and the salt bridge addition mutant Q307D showed 9.15% thermostability enhancement than the wild-type both without the pH and temperature optimum changed. It proved salt bridges play a key role in E. coli AppA phytase's thermostability and the α/β-domain of AppA may be sensitive to heat. Salt bridges and the α/β-domain of AppA should have high priority to think about to enhance AppA's thermostability for commercial application. Besides, molecular dynamics simulation was used for salt bridges analysis.
    Journal of Bioscience and Bioengineering 01/2013; · 1.74 Impact Factor
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    ABSTRACT: Based on the strategy of changing pH-stability profiles by altering pKa values of catalytic residues, rational protein engineering was applied to improve alkalophilic adaptation of Aspergillus niger endoxylanase XynB. Computational predictions and molecular modeling were carried out using PROPKA server and SWISS-MODEL server, respectively. Three endoxylanase mutant of S108V, N151E, and Q178R, in which the pKa values of either catalytic glutamate residues shifted, were generated. In agreement with expectation, the variant of Q178R improved alkalophilic performances. The mutant Q178R raised the optimum pH of XynB from 5.5 to 6.0 and retained 37% of the maximum activity at pH 8.0. Interestingly, the pKa values of Glu84 and Glu175 in Q178R are 7.91 and 6.32, respectively. The pKa of Glu175 is lower than that of Glu84, as opposed to the fact that the pKa of Glu84 is lower than that of Glu175 in other GH11 xylanases. It indicated that Glu175 may convert into a nucleophile residue and Glu84 into an acid/base residue.
    Journal of Bioscience and Bioengineering 01/2013; · 1.74 Impact Factor
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    ABSTRACT: Due to our previous research, mainly the thermostable mutants Q307D, Y311K, and I427L, we conjectured that Escherichia coli AppA phytase's C-terminal plays an important role in its thermostability, and AppA begins to collapse from the C-terminal when at a higher temperature. So here we constructed C-lose mutant to prove it. The residual activities of the wild-type AppA phytase and C-lose were 31.42 and 70.49 %, respectively, after being heated at 80 °C for 10 min. The C-terminal deletion mutant C-lose showed 39.07 % thermostability enhancement than the wild-type both without the pH and temperature optimum changed. It proved the C-lose plays a key role in E. coli AppA phytase's thermostability.
    Current Microbiology 12/2012; · 1.52 Impact Factor
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    ABSTRACT: Xylanase is one of the most important hemicellulases in industry. However, its low thermostability limits its applications. In this study, one thermostable xylanase-producing strain 400264 was obtained from screening 11 Aspergillus niger strains (producing thermotolerant xylanase), and the optimum temperature of crude xylanase extracted from it was 55°C. Original activity of the crude xylanase is 64% at 60°C and 55% at 85°C with an incubation time of 30 min, respectively. After the expression of recombinant xylanase gene (xynA/xynB), the XYNB (xylanase B) showed higher thermostability than XYNA (xylanase A). Recombinant enzyme XYNB retained 94% of its activity for 10 min at 85°C, while XYNA with no activity left. Site-directed mutagenesis was performed to replace Ala33 of XYNB by Ser33 resulting 19% decrease in enzyme activity after incubating at 85°C for 30 min. It suggested that the Ala33 residue may have a certain effect on the thermophilic adaptation of xylanase.
    Current Microbiology 01/2011; 62(1):242-8. · 1.52 Impact Factor
  • Rui Zhao, Yu Cao, Hui Xu, Linfeng Lv, Dairong Qiao, Yi Cao
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    ABSTRACT: The unicellular green alga Dunaliella salina (Dunal) Teodor. is a novel model photosynthetic eukaryote for studying photosystems, high salinity acclimation, and carotenoid accumulation. In spite of such significance, there have been limited studies on the Dunaliella genome transcriptome and proteome. To further investigate D. salina, a cDNA library was constructed and sequenced. Here, we present the analysis of the 2,282 expressed sequence tags (ESTs) generated together with 3,990 ESTs from dbEST. A total of 4,148 unique sequences (UniSeqs) were identified, of which 56.1% had sequence similarity with Uniprot entries, suggesting that a large number of unique genes may be harbored by Dunaliella. Additionally, protein family domains were identified to further characterize these sequences. Then, we also compared EST sequences with different complete eukaryotic genomes from several animals, plants, and fungi. We observed notable differences between D. salina and other organisms. This EST collection and its annotation provided a significant resource for basic and applied research on D. salina and laid the foundation for a systematic analysis of the transcriptome basis of green algae development and diversification.
    Journal of Phycology 01/2011; 47(6). · 2.24 Impact Factor
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    ABSTRACT: His(354) and His(358), two highly conserved histidines in Xenopus laevis (6-4) photolyase [equivalent to His(401) and His(405), in Dunaliella salina (6-4) photolyase], are critical for photoreactivation. They act as a base and an acid, respectively. However, the remaining high repair activity when the pH value is higher than the pKa of histidine suggests the involvement of other basic amino acids in photoreactivation. According to the results of in vivo enzyme assay and three-dimension structural model of Dunaliella salina (6-4) photolyase we hypothesized that Lys(281) might be involved in the photoreactivation over the pH range from 10.0 to 11.0. To test this, we generated two mutant forms of the (6-4) photolyase, K281G and K281R mutant, by overlap extension polymerase chain reaction, and performed the enzyme assay with these mutants. From these results we conclude that the Lys(281), which is highly conserved in (6-4) photolyases, participates in the photoreactivation and acts as an acid to donate a proton to His(401) when the environmental pH is higher than the pKa value of histidine.
    Current Microbiology 01/2011; 62(1):146-51. · 1.52 Impact Factor
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    ABSTRACT: The analysis of individual gene product should enable to clarify the role of a particular enzyme in a complex xylanase system of A. niger. The two genes encoding precursors of co-produced endo-1,4-β-D-xylanases, xynA1 and xynB, were isolated from Aspergillus niger SCTCC 400264 (SCTCC, China) by using RT-PCR technique and then successfully expressed in Escherichia coli BL21. The nucleotide sequences of the xynA1 and xynB genes revealed that they were only 52.5% homology to each other. Characterization of the recombinant enzymes revealed the different properties: the specific activity of recombinant XYNA1 was 16.58 U/mg compared to 1201.7 U/mg for recombinant XYNB; The optimum temperature and pH of the recombinant XYNA1 were 35 °C and 3.0, respectively, whereas the corresponding values for the recombinant XYNB were 55 °C and 5.0, respectively; The recombinant XYNB showed much more thermostability than recombinant XYNA1; The recombinant XYNB showed 94% of maximal activity after incubating in water for 60 min at 60 °C compared to no activity for recombinant XYNA1. Various metal ions had different effects on activity between the two recombinant xylanases.
    Brazilian Journal of Microbiology 07/2010; 41(3):778-86. · 0.76 Impact Factor
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    ABSTRACT: In order to improve the thermostability of Escherichia coli AppA phytase, Error-prone PCR was used to randomize mutagenesis appA gene, and a gene mutation library was constructed. A mutant I408L was selected from the library by the method of high-throughput screening with 4-methyl-umbelliferylphosphate (4-MUP). The appA gene of the mutant was cloned and expressed in E. coli Origami (DE3). The recombinant protein was purified by Ni-affinity chromatography, and the enzymatic features were analyzed. The results indicated that AppA phytase activities of mutant I408L and wild-type (WT) strain remained at 51.3 and 28%, respectively, after treatment at 85°C for 5 min. It means that the thermostability enhancement of AppA phytase I408L was 23.3% more as compared with WT. The K (m) of both phytase were 0.18 and 0.25 mM, respectively, which indicated that the catalyzing efficiency of I408L was improved. AppA phytase of mutant I408L showed a significant enhancement against trypsin, which was nearly three times compared with WT. In addition, AppA phytase of mutant could be activated by Mg(2+) and Mn(2+); in contrast, it could be inhibited by Ca(2+), Co(2+), Cu(2+), and K(+) in varying degrees, and the enzymatic activity was almost lost the presence of Fe(3+) and Zn(2+). It appears that screening thermotolerant phytase of E. coli by high throughput screening with a fluorescence substrate is a fast, simple, and effective method. The mutant I408L obtained in this study could be used for the large-scale commercial production of phytase.
    Current Microbiology 03/2010; 61(4):267-73. · 1.52 Impact Factor
  • Chinese Journal of Appplied Environmental Biology. 01/2010; 16(1):18-22.

Publication Stats

58 Citations
46.85 Total Impact Points


  • 2004–2014
    • Sichuan University
      • • College of Life Sciences
      • • Key Laboratory of Bio-resource and Eco-environment (MOE)
      Hua-yang, Sichuan, China
  • 2013
    • Sichuan Normal University
      Hua-yang, Sichuan, China