Abstract:The somatic embryogenesis in plant is a very complicated and highly ordered process, which is regulated by many internal and external factors. Among them, gene expression and regulation are key factors. Genes encoding regulatory proteins, for example PLANT GROWTH ACTIVATOR, LEAFY COTYLEDON, BABY BOOM, SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE and PICKLE, interact with each other and form a complicated regulatory network. Recent progress on this regulatory network was reviewed on the basis of our study on the PLANT GROWTH ACTIVATOR 37 gene. In addition, future research perspectives on plant somatic embryogenesis were discussed.

Abstract:To study if Solanum nigrum hairy roots can be used for phytoremediation of Cd contamination, we investigated the effects of cadmium (Cd) alone, and in combination with different concentrations of CaCl2, on growth, activities of superoxide dismutase (SOD) and peroxidase (POD) and Cd absorption by hairy roots of S. nigrum L. var pauciflorum. The results showed that Cd concentrations of lower than 50 μmol/L enhanced the growth of hairy roots, while higher than 100 μmol/L inhibited growth and decreased the number of branched roots, also causing the root tips to become brown and shorter in length. In comparison with a control, the soluble protein content, the activities of SOD and POD in hairy roots cultures showed a trend of first increased and then gradually decreased, while the malondialdehyde (MDA) content significantly increased, when increasing the Cd concentrations. Cd concentration of 100 μmol/L or 300 μmol/L in combination with 10–30 mmol/L CaCl2 resulted in a decreased content of soluble protein and MDA in the hairy roots, but an enhanced SOD activity. The increased POD activities were observed when cultured in 100 μmol/L Cd and 10–30 mmol/L CaCl2 but decreased when cultured in 300 μmol/L Cd and 10–30 mmol/L CaCl2. Atomic Absorption Spectrometry determination showed that the Cd absorbed and by the hairy roots increased along with the increase of Cd concentration. The exogenous addition of 10–30 mmol/L CaCl2 could reduce the toxicity of Cd. This was achieved on one hand by reducing the absorption of Cd, on the other hand by decreasing the lipid peroxidation through regulating the activities of antioxidant enzymes SOD and POD in the hairy roots.

Abstract:Directed evolution of transcription factors can be employed to effectively improve the phenotypes which are controlled by multiple genetic loci. In this study, we used error-prone PCR for the directed evolution of SPT3, which is the component of yeast Spt-Ada-Gcn5-acetyltransferase (SAGA) complex responsible for the transcription of stress-related genes, and studied its effect on the improvement of ethanol tolerance. Mutant library was constructed by ligating the error-prone PCR products with a modified pYES2.0 plasmid, and the expression plasmids were subsequently transformed to yeast industrial strain Saccharomyces cerevisiae 4126. One mutant strain M25 showing superior growth in presence of 10% ethanol was selected. M25 produced 11.7% more ethanol than the control strain harboring the empty vector when 125 g/L glucose was used as substrate. This study revealed that SPT3 is an important transcription factor for the metabolic engineering of yeast ethanol tolerance.

Abstract:In order to clone and express alcohol dehydrogenase II (ADH2) gene from Saccharomyces cerevisiae in E. coli BL21 (DE3) efficiently, we extracted the total RNA as template and obtained ADH2 gene by RT-PCR and connected ADH2 gene to pTAT plasmids to gain recombinant expression plasmid pTAT-ADH2, then transformed this recombinant expression plasmid pTAT-ADH2 into E. coli BL21 (DE3). The recombinant was induced by IPTG to express ADH2. After purification, ADH2 activity was tested in vitro and toxicologic test was done in mouse. Sequence test showed that the acquired fragments exhibited 90% homology to ADH2 gene sequence from GenBank report. The target gene expressed efficiently and took up to approximant 50% of total protein by SDS-PAGE and band scanning analysis. The purified protein exhibited the identified activity through biochemical test and mouse toxicological test. As a result, the acquired ADH2 gene was highly homology to the published sequence and expressed at a high level in E. coli BL21 (DE3), more importantly, ADH2 proved to have ethanol dehydrogenase activity.

Abstract:Clostridium tyrobutyricum is suitable for simultaneous saccharification and fermentation of lignocellulosic. It can produce butyric acid, acetic acid as its main fermentation products from a wide variety of carbohydrates such as glucose, xylose, cellobiose and arabinose. In order to decrease acetic acid content and increase butyric acid content in C. tyrobutyricum, we replaced genes on the acetic acid fermentation pathway with genes on the butyric acid fermentation pathway. Three genes were selected. They were acetyl-CoA acetylrtansfers gene (thl) which is the key enzyme gene associated with acetic acid fermentation pathway from Clostridium acetobutylicum, erythromycin gene (em) from plasmid pIMP1 and phosphotransacetylase gene (pta) which is the key enzyme gene associated with butyric acid fermentation pathway from C. tyrobutyricum. We fused these genes with pUC19 to construct nonreplicative integrated plasmids pUC19-EPT. Then we transformed pUC19-EPT into C. tyrobutyricum through electroporation. The recombinant transformants grown on plates containing erythromycin were validated by PCR. A mutant whose pta gene was displaced by thl gene on the chromosome was selected. In the fermentation from glucose, the mutant’s yield of butyric acid is 0.47, increased by 34% compared with wild type; and the yield of acetic acid is 0.05, decreased by 29% compared with wild type.

Abstract:The kinetic mechanisms of two key enzymes in the biotransformation of glycerol to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae, glycerol dehydrogenase (GDH) and 1,3-propanediol oxidoreductase (PDOR), was characterized. Kinetics on initial velocity and product inhibition revealed that GDH and PDOR follow an ordered Bi-Bi sequential mechanism. Kinetic models for GDH and PDOR showed that the oxidation reaction catalyzed by GDH was the rate-limiting step in coupled enzymatic reaction when the GDH/PDOR was 1:1, and the NAD+ was the main form of coenzyme in the reaction. Knowledge about the kinetic mechanisms will be helpful to understand how these enzymes is regulated, which will be useful for further enzyme catalysis and metabolic engineering studies.

Abstract:An ammonium-tolerant mutant of Actinobacillus succinogenes, YZ25, was obtained in the medium containing 61?242 mmol/L NH4+ after DES mutagenesis. Succinic acid produced by the mutant YZ25 reached 32.68 g/L when the medium contains 50 g/L glucose and 121 mmol/L ammonium, which was increased by 180.5% compared with that of the parent strain. The effects of different ammonium salts on the growth of the mutant and its metabolic response to high ammonium concentrations were investigated. The results showed that low ammonium concentration could improve the specific growth rates of the mutants, while high ammonium concentration inhibited cell growth. The ammonia-nitrogen half-inhibition constants (Ki) for different ammonium salts were as follows: 215 mmol/L for (NH4)2SO4, 265 mmol/L for NH4HCO3, 235 mmol/L for NH4Cl, and 210 mmol/L for NH4NO3. The process of ammonium inhibition on the mutant YZ25 was investigated in 3.0 L stirred fermentor. When NH4OH was used to buffer the pH, cell growth was not inhibited. However, production of succinic acid and consumption of glucose gradually decreased when cells entered the stationary phase, and the glucose could not be utilized completely at the end of fermentation. The possible ammonium inhibition mechanism was discussed based on the metabolic pathway of A. succinogenes.

Abstract:Biomass carbohydrates assimilation and lipid accumulation by Mortierella isabellina M2 strain were investigated. Corn fiber hydrolysate was specially studied. The results showed M. isabellina M2 strain achieved growth and lipid accumulation while glucose, xylose, mannose and arabinose were introduced as single carbon source, respectively. When M. isabellina M2 strain was cultivated on corn fiber hydrolysate with 6% sugars concentration, the biomass reached 18.2 g/L, the lipid content of dry mycelia was 45.7%, and the lipid yield achieved 8.3 g/L. It provided a promising perspective for microbial oils production with biomass hydrolysates.

Abstract:We isolated the strain MBL13 with high collagenase productivity from the soil of piled up animal bones. It was identified as Bacillus cereus. We purified and characterized Bacillus cereus collagenase (BCC). The molecular weight of BCC was 38.0 kDa and the optimum temperature and pH for the enzyme activity were 40?C and 8.0 respectively. The enzyme was stable when the temperature was below 50?C, but only retained 10% activity when kept at 60?C for 1 h. The enzyme activity was stable between pH 7.0–8.5. Some metal ions such as Ca2+, Zn2+, Mg2+ enhanced the enzyme activity, and Cu2+ brought the obvious inhibition. In addition, EDTA and EGTA could inhibit the enzyme activity. We suggested that the purified enzyme was a member of the metalloproteases. Based on the experiment of substrate specificity, we found that the purified enzyme was bone collagenolytic protease, and had a much stronger capacity of hydrolysis for type I collagen than that for type II collagen and type III collagen. By BCC hydrolyzing bone collagen, we obtained polypeptides with different chain lengths. The comparative test indicated that the hydrolysis capacity of BBC was higher than that of standard type I collagenase. The results introduced a new strain and a novel collagenolytic protease for industrial enzyme.

Abstract:To obtain the pure and soluble P51 antigen of HIV-1 strain CN54, we transformed the Escherichia. coli strain BL21 codonplus-RIL with recombinant plasmid pTHioHisA51 which carries a gene encoding the Polymerase (Pol) P51 antigen of HIV-1 CN54 formerly, and induced protein expression by IPTG. We purified the recombinant protein with Chelating Sepharose FF-Ni and DEAE-Sepharose FF column chromatography, then renatured the recombinant protein by dialyzation. Purified protein was identified by Western blotting. We labeled and coated antigen P51 in a dual-antigen sandwich system, and tested it with serum samples from HIV-infected individuals. The results showed that P51 was expressed as inclusion body, and represented about 50% of total cellular protein. After purification and renaturation, the purity of P51 was up to 95%. Western blotting and sandwich ELISA demonstrated that recombinant P51 had good anti-HIV antibody specificity and sensitivity. The results suggested that recombinant HIV-1 P51 can be prepared as diagnostic reagent, and provides valuable support for HIV-1 detection and vaccine research.

Abstract:In order to get soluble TNF? receptor (sTNFR) II with good neutralizing activity against TNF?, we constructed the fusion gene sTNFRII-gAD, which encoded human sTNFR II and the globular domain of adiponectin (gAD), and then expressed it in mammalian cells and analyzed its anti-TNFα activity. First, sTNFRII cDNA was obtained by RT-PCR from the total RNA of human peripheral blood lymphocytes, and fused in frame with gAD gene. Then, the fusion gene sTNFRII-gAD was cloned into the expression vector pAAV2neo to result in the plasmid pAAV2neo-sTNFRII-gAD. By immunofluorescent staining with monoclonal antibody either against TNFRII or against adiponectin, we demonstrated that the pAAV2neo-sTNFRII-gAD-transiently-transfected BHK-21S cells were positive. To obtain G418-resistant BHK-21S/pAAV2neo-sTNFRII-gAD cells, we cultured the transfected BHK-21S cells above in 10% FBS containing DMEM media with 800 μg/mL G418 for 15 days, and changed the serum-containing culture media to a serum-free chemically defined media so as to change the cells culturing style from adhesion to suspension. 24 hours later, we harvested the supernatant of the culture for sTNFRII-gAD fusion protein characterization and anti-TNFα activity analysis. With monoclonal antibody either against TNFRII or against adiponectin, the Western blotting analysis showed that the sTNFRII-gAD fusion protein was expressed and existed as monomer, trimer and multimer forms in the supernatant. The bioactivity assay demonstrated that the sTNFRII-gAD fusion protein had the ability to neutralize TNFα so as to inhibit the cytotoxicity of TNFα on L929 cells. Put together, this study has laid the groundwork for large-scale preparation of sTNFRII-gAD fusion protein.

Abstract:TNFR-Fc is an important fusion protein that has great potential in therapeutic and diagnostic applications. We developed an efficient fed-batch process for GS-CHO cells to produce TNFR-Fc. The rationale of this fed-batch process relies on the supply of sufficient nutrients to meet the requirements of cell metabolism. The optimal feed medium was designed through ration design. A metabolically responsive feeding strategy was designed and dynamically adjusted based on the residual glucose concentration determined off-line. In this process, the maximal viable cell density and antibody concentration reached above 9.4×106 cells/mL and 207 mg/L, respectively. Compared with the batch process, the newly developed fed-batch process increased the cell yield by 3.4 fold and the final antibody concentration by 3 fold. This fed-batch process would therefore facilitate the production of therapeutic antibody by GS-CHO cells.

Abstract:A bioprocess intensification strategy that combines both elicitation and in situ absorption was developed to improve the production of taxuyunnanine C (Tc) in suspension culture of Taxus chinensis. When 100 μmol/L methyl jasmonate was added as an elicitor on Day 7, the Tc content and yield increased 3.6 and 3.3 times respectively, however the cell growth was reduced by 30%. Significant improvement in Tc yield was observed when an absorbent XAD-7 was added on different time of the culture period. The optimum Tc production was achieved when 100 g/L XAD-7 was added simultaneously with 100 μmol/L methyl jasmonate on Day 7. The maximum Tc yield of 477.4 mg/L was obtained on Day 21 of the culture, being 6.3-fold of the control and 1.9-fold of the 100 μmol/L methyl jasmonate treatment alone. In the combined treatment, 94% of the Tc produced were secreted outside of the cells and absorbed on XAD-7 absorbents. The results demonstrated that the process strategy combining elicitation and in situ absorption was effective to intensify the Tc biosynthesis via elicitation with the removal of product feedback inhibition via absorption, presenting a great potential in commercial applications.

Abstract:In an effort to generate a desired expression construct for making heart-specific expression transgenic zebrafish, a Tol2 plasmid, which can drive EGFP reporter gene specifically expressed in the heart, was modified using subcloning technology. An IRES fragment bearing multiple cloning site (MCS) was amplified directly from pIRES2-EGFP plasmid and was inserted between the CMLC2 promoter and EGFP fragment of the pDestTol2CG vector. This recombinant expression plasmid pTol2-CMLC2-IRES-EGFP can drive any interested gene specifically expressed in the zebrafish heart along with EGFP reporter gene. To test the effectiveness of this new expression plasmid, we constructed pTol2-CMLC2-RED-IRES-EGFP plasmid by inserting another reporter gene DsRed-Monome into MCS downstream of the CMLC2 promoter and injected this transgenic recombinant plasmid into one-cell stage embryos of zebrafish. Under fluorescence microscope, both the red fluorescence and the green fluorescence produced by pTol2-CMLC2-RED-IRES-EGFP were detected specifically in the heart tissue in the same expression pattern. This novel expression construct pTol2-CMLC2-IRES-EGFP will become an important tool for our research on identifying heart development candidate genes’ function using zebrafish as a model.

Abstract:Protozoan ciliates are a group of unicellular eukaryotes. The special characteristics of stop codons usage in termination of protein biosynthesis in ciliates cells makes them an ideal model to study the mechanism of stop codon recognition of polypeptides release factors. To localize the functional positions of biomolecules in ciliates cell, we constructed a macronuclear artificial chromosome containing a gene encoding red fluorescence protein (EoMAC_R) based on the structural characteristics of ciliates chromosome. Three factors, L11, eRF1a, and eRF3 that are involved in termination process of protein synthesis were colocalized in Euplotes octocarinatus cells by using novel EoMAC_R and the previously constructed EoMAC_G. The results indicated that protein synthesis mainly occurred inside the “C” shape macronucleus, suggesting that EoMAC could be a useful tool for localizing biomolecules in ciliates cell.

Abstract:This study was to acquire recombinant protein of von Willebrand factor cleaving protease (ADAMTS13, a disintegrin and metalloprotease with a thromboSpondin type 1 motifs 13), for further studies on its biological function in thrombosis and hemostasis. We transfected the Hela cells with the plasmid pSecTag-ADAMTS13 by lipofectamine. A positive cell cloning was selected by hygromycin-B. The recombinant protein was purified with Ni-NTA agarose column by gradient imidazole. The purity and immune activity of purified products were identified with SDS-PAGE and Western blotting respectively. We also measured the enzymatic activity of recombinant protein (rADAMTS13) by GST-His two-site ELISA assay. The results showed that we successfully constructed Hela cells ADAMTS2-4 which expressed high level of rADAMTS13. We received about 5.8 mg recombinant protein in culture supernantants per liter purified with Ni-NTA column. The protein formed a main lane at the position of 190 kDa with SDS-PAGE and reacted with polyclonal antibody against ADAMTS13 by Western blotting. The amount of rADAMTS13 activity was 6.4 U/mL, according to the normal plasma defined as 1 U/mL. In conclusion, rADAMTS13 protein had high purity, immune activity and good enzymatic activity, which could establish the experimental foundation for further research on biological function and mechanism of this unique metalloprotease.

Abstract:In order to research the bioactivity of kallistatin (Kal), we obtained the recombinant Kal using Pichia pastoris expression system. Kal cDNA was amplified from pAAV-Kal and inserted into pPIC9 vector to generate a recombinant vector of pPIC9-Kal. Then, pPIC9-Kal was linearized and transformed into Pichia pastoris strain GS115 (His4) by electroporation. The positive transformants were selected by MD plate and confirmed by PCR. High level of Kal was obtained in BMMY medium (pH 7.0) after 96 hours induction of 29?C and 2% methanol, with the highest yield of 14 mg/L in shake flask culture. Kal protein was purified from the supernatant with Phenyl Superose and Heparin Sepharose FF chromatograph. The recombinant Kal had a molecular weight of 58 kDa with 98% purity, showing by SDS-PAGE. Moreover, it had a high peroxidase activity (163±4) U/(mg?min), which could protect LX-2 cell against oxidation of H2O2. Recombinant Kal also effectively inhibited HUVEC proliferation. In this report, we successfully established the expression system using Pichia pastoris and obtained the bioactive recombinant human Kal. It lays a foundation for its further anti-cancer therapy.

Abstract:To produce TEM-116 extended-spectrum-beta-lactamase (ESBL) from recombinant bacteria in a cost-effective way, we purified and renatured the recombinant TEM-116 ESBL from the inclusion bodies by Ni2+-NTA affinity and gel filtration chromatography through subcloning the blaTEM-116 into expression vector pET28a(+), transforming into Escherichia coli BL21(DE3) and inducing with IPTG. We characterized the purified protein that had the molecular weight of 30 kDa and specific activity of 476 IU/mg. The recombinant TEM-116 ESBL showed higher efficiency in eliminating penicillin and cephalosporin in vitro and in vivo. Specifically, the recombinant TEM-116 ESBL could eliminate 7000 mg penicillin G (PG) when used at 10.0 IU in 1 L fermentation medium. When used at 320.0 IU, it could also degrade a mix of PG, ampicillin and cefazolin each at 200 mg in 1 L of urine. In milk, 1.0–2.5 IU of the recombinant enzyme could remove 80 U/L of PG. The recombinant enzyme was fully active at the temperature ranged from 4°C to 37°C. Furthermore, the recombinant enzyme used at 2.0×104–2.3×104 IU/(kg?bw) (body weight) eliminated 8.0×104–9.1×104 μg/(kg?bw) PG in mouse models in vivo. The recombinant TEM-116 ESBL has the potential as a tool enzyme in food and environmental protection to eliminate harmful residues of antibiotics.

Abstract:Spore coat proteins, such as CotB, CotC, CotG et al, are able to efficiently display exogenous protein on spore surface for preparing oral vaccines or enzymes. CotX is another structural protein of spore coats of Bacillus subtilis. To investigate whether CotX could carry target protein onto the spore surface, we constructed a recombinant integrative plasmid, designated as pJS749, which carries a recombinant cotX-gfp gene under the control of the cotX promoter. We transformed pJS749 into Bacillus subtilis 168(trp-), an α-amylase inactivated mutant DRJS749 was selected and confirmed to be a double crossover integrant, where cotX-gfp fragment was integrated into the chromosome. After induction of spore formation, significant green fluorescence was observed on spore surface of strain DRJS749 under fluorescent microcopy. This suggests that CotX is associated with the outer part of the coat. CotX can therefore be used as a molecular vehicle for spore surface display of exogenous proteins.

Abstract:A magnetic separator was used to separate magnetic bacteria based on their magnetotactic characteristics. Acidithiobacillus ferrooxidans, a bacterium that could synthesize intra-cellular nanometer magnetic particles, was investigated as an example. Strong magnetic and weak magnetic cells were separated and collected. On average, the number of the magnetic particles present in the strong magnetic cells is more than that of the weak magnetic cells. Moreover, semisolid-plate magnetophoresis showed that the magnetotaxis of strong magnetic cells was stronger than the weak magnetic cells. These results suggest that the magnetic separator can be used to isolate the magnetic bacteria, which will facilitate the research of magnetic bacteria.