Ziduo Liu

Huazhong Agricultural University, Wu-han-shih, Hubei, China

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Publications (66)174.91 Total impact

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    ABSTRACT: A novel cold active esterase, EstLiu was cloned from the marine bacterium Zunongwangia profunda, overexpressed in E. coli BL21 (DE3) and purified by glutathione-S transferase (GST) affinity chromatography. The mature esterase EstLiu sequence encodes a protein of 273 amino acids residues, with a predicted molecular weight of 30 KDa and containing the classical pentapeptidase motif from position 156 to 160 with the catalytic triad Ser158-Asp211-His243. Although, EstLiu showed 64% similarity with the hypothetical esterase from Chryseobacterium sp. StRB126 (WP_045498424), phylogenetic analysis showed it had no similarity with any of the established family of lipases/esterases, suggesting that it could be considered as a new family. The purified enzyme showed broad substrate specificity with the highest hydrolytic activity against p-nitrophenyl butyrate (C4). EstLiu showed remarkable activity (75%) at 0 °Cand the optimal activity at pH 8.0 and 30 °C with good thermostability and quickened inactivation above 60 °C. EstLiu retained 81, 103, 67 and 78% of its original activity at 50% (v/v) in ethanol, isopropanol, DMSO and ethylene glycol, respectively. In the presence of Tween 20, Tween 80 and Triton X-100, EstLiu showed 88, 100 and 117% of relative activity. It is also co-factor independent. The high activity at low temperature and desirable stability in organic solvents and salts of this novel family esterase represents a good evidence of novel biocatalyst. Overall, this novel enzyme showed better activity than previously reported esterases in extreme reaction conditions and could promote the reaction in both aqueous and non-aqueous conditions, indicating its great potential for industrial applications.
    No preview · Article · Apr 2016 · Enzyme and Microbial Technology
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    ABSTRACT: Glycine oxidase (GO) has great potential for use in biosensors, industrial catalysis and agricultural biotechnology. In this study, a novel GO (BliGO) from a marine bacteria Bacillus licheniformis was cloned and characterized. BliGO showed 62% similarity to the well-studied GO from B. subtilis. The optimal activity of BliGO was observed at pH 8.5 and 40 °C. Interestingly, BliGO retained 60% of the maximum activity at 0 °C, suggesting it is a cold-adapted enzyme. The kinetic parameters on glyphosate (Km, kcat and kcat/Km) of BliGO were 11.22 mM, 0.08 s−1, and 0.01 mM−1 s−1, respectively. To improve the catalytic activity to glyphosate, the BliGO was engineered by directed evolution. With error-prone PCR and two rounds of DNA shuffling, the most evolved mutant SCF-4 was obtained from 45,000 colonies, which showed 7.1- and 8-fold increase of affinity (1.58 mM) and catalytic efficiency (0.08 mM−1 s−1) to glyphosate, respectively. In contrast, its activity to glycine (the natural substrate of GO) decreased by 113-fold. Structure modeling and site-directed mutation study indicated that Ser51 in SCF-4 involved in the binding of enzyme with glyphosate and played a crucial role in the improvement of catalytic efficiency.
    No preview · Article · Jan 2016 · Enzyme and Microbial Technology
  • Zhong Zou · Sunrui Chen · Ziduo Liu · Meilin Jin
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    ABSTRACT: A novel strain of H3N8 influenza virus was isolated from domestic pigeons during the avian influenza virus (AIV) surveillance in wet markets in Anhui, China, during 2013. The virus was characterized by whole-genome sequencing with subsequent genetic comparison and phylogenetic analysis. Phylogenetic analysis revealed that the NA gene of AIV mapped to the North American lineage, and the remaining seven genes belong to a Eurasian lineage. These findings indicated that this H3N8 virus is a novel nature reassortant virus. Comparison of the hemagglutinin amino acid sequences indicated 9 substitutions. One substitution caused the loss of a potential glycosylation site, and six substitutions were not previously observed in avian H3 isolates. Q226 and T228 at the receptor binding sites suggested that Anhui-08 preferentially binds to a-2,3-linked sialic acid receptors, and the cleavage site sequence showed a low pathogenic feature. Animal experiments further confirmed that A/pigeon/Anhui/08/2013 (H3N8) is low or in pigeons. The results improve our understanding of these viruses as they evolve and also provide important information to aid ongoing risk assessment analyses because these zoonotic influenza viruses continue to circulate and adapt to new hosts.
    No preview · Article · Nov 2015 · Virus Genes
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    ABSTRACT: A cbd gene was cloned into the C-terminal region of a lip gene from Geobacillus stearothermophilus. The native lipase (43.5kDa) and CBD-Lip fusion protein (60.2kDa) were purified to homogeneity by SDS-PAGE. A highly stable cellulosic nanogel was prepared by controlled hydrolysis of microcrystalline cellulose onto which the CBD-lip fusion protein was immobilized through bio-affinity based binding. The nanogel-bound lipase showed optimum activity at 55°C, and it remains stable and active at pH 10-10.5. Furthermore, the immobilized lipase showed an over two-fold increase of relative activity in the presence of DMSO, isopropanol, isoamyl alcohol and n-butanol, but a mild activity decrease at a low concentration of methanol and ethanol. The immobilized biocatalyst retained ∼50% activity after eight repetitive hydrolytic cycles. Enzyme kinetic studies of the immobilized lipase showed a 1.24 fold increase in Vmax and 5.25 fold increase in kcat towards p-NPP hydrolysis. Additionally, the nanogel bound lipase was tested to synthesize a biodiesel ester, ethyl oleate in DMSO. Kinetic analysis showed the km 100.5±4.3mmol and Vmax 0.19±0.015mmolmin(-1) at varied oleic acid concentration. Also, the values of km and Vmax at varying concentration of ethanol were observed to be 95.9±13.9mmol and 0.22±0.013mmolmin(-1) respectively. The maximum yield of ethyl oleate 111.2±1.24mM was obtained under optimized reaction conditions in organic medium. These results suggest that this immobilized biocatalyst can be used as an efficient tool for the biotransformation reactions on an industrial scale.
    No preview · Article · Nov 2015 · Colloids and surfaces B: Biointerfaces
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    ABSTRACT: Nematodes are known to be harmful to various crops, vegetables, plants and insects. The present study reports that, chitin upregulates the activity of chitinase (20%) and nematicidal potential (15%) of Pseudomonas aeruginosa. The chitinase gene (pachi) from P. aeruginosa was cloned, and its nematicidal activity of pachi protein against Caenorhabditis elegans was studied. The mortality rate induced by pachi increased by 6.3-fold when in association with Cry21Aa from Bacillus thuringiensis. Pachi efficiently killed C. elegans in its native state (LC50 = 387.3 ± 31.7 μg/ml), as well as in association with Cry21Aa (LC50 = 30.9 ± 4.1 μg/ml), by degrading the cuticle, egg shell and intestine in a relatively short time period of 24 h. To explore the nematidal potential of chitinase, six fusion proteins were constructed using gene engineering techniques. The CHACry showed higher activity against C. elegans than others owing to its high solubility. Notably, the CHACry showed a synergistic factor of 4.1 versus 3.5 a mixture [1:1] of pachi and Cry21Aa. The present study has identified eco-friendly biological routes (e.g., mixed proteins, fusion proteins) with potent nematicidal activity, which not only can help to prevent major crop losses but also strengthen the agro-economy and increase gross crop yield.
    Full-text · Article · Sep 2015 · Scientific Reports
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    ABSTRACT: Lipolytic enzymes with unique physico-chemical characteristics are gaining more attention for their immense industrial importance. In this study, a novel lipolytic enzyme (Est11) was cloned from the genomic library of a marine bacterium Psychrobacter pacificensis. The enzyme was expressed in Eschrichia coli and purified to homogeneity with molecular mass of 32.9 kDa. The recombinant Est11 was able to hydrolyze short chain esters (C2 to C8) and displayed an optimum activity against butyrate ester (C4). The optimal temperature and pH were 25 (o)C and 7.5, respectively. Est11 retained more than 70% of its original activity at 10°C, suggesting that it was a cold-active esterase. The enzyme was highly active and stable at high concentration of NaCl (5M). Further, incubation with ethanol, isopropanol, propanediol, DMSO, acetonitrile and glycerol rendered remarkable positive effects on Est11 activity. Typically, even at the concentration of 30% (v/v), ethanol, DMSO and propanediol increased Est11 activity by 1.3, 2.0 and 2.4-folds, respectively. This new robust enzyme with remarkable properties like cold-adaptability, exceptional tolerance to salt and organic solvents provides us a promising candidate to meet the needs of some harsh industrial processes. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Jul 2015 · International journal of biological macromolecules
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    ABSTRACT: Glyphosate is a broad spectrum herbicide widely used throughout the world, and it could be degraded by glycine oxidase (GO) through C-N bond cleavage. For a better understanding of the structure-function relationship and improving the activity of B3S1 (GO from Bacillus cereus), DNA shuffling was performed. A mutant B4S7 (TheKm,Vmax, kcat and kcat/Km values on glyphosate were 0.1mM, 0.002401mMmin(-1), 3.62min(-1) and 36.2mM(-1)min(-1), respectively. The four parameters on glycine were 50.34mM, 0.001983mMmin(-1), 2.18min(-1) and 0.04mM(-1)min(-1), respectively) was obtained from 10,000 clones, which presented a 3.9-fold increase of the specificity constant (the kcat/Km ratio between glyphosate and glycine) compared with B3S1. Especially, the Km value of B4S7 to glyphosate was much less than those of the reported GO. Structure modeling and molecular docking indicated that the novel mutation point F247S was close to the active site of the enzyme. To identify the role of the site, the remaining 19 amino acids were introduced into the site by site-saturation mutagenesis. The result showed that compared with B3S1, the specificity constant of mutant F247S and F247R increased 0.64-fold and 1.04-fold, respectively. While the specificity constant of mutant F247E decreased 2.01-fold. Therefore, the site 247 plays a crucial role in regulating the substrate specificity. This study provides new information on the structure-function relationship of glycine oxidase and the development of glyphosate-tolerant crops. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · May 2015 · International Journal of Biological Macromolecules
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    ABSTRACT: The accumulation of a considerable quantity of gibberellin fermentation residue (GFR) during gibberellic acid A3 (GA3) production not only results in the waste of many resources, but also poses a potential hazard to the environment, indicating that the safe treatment of GFR has become an urgent issue for GA3 industry. The key to recycle GFR is converting it into an available resource and removing the GA3 residue. To this end, we established a co-bioconversion process in this study using house fly larvae (HFL) and microbes (Corynebacterium variabile) to convert GFR into insect biomass and organic fertilizer. About 85.5% GA3 in the GFR was removed under the following optimized solid-state fermentation conditions: 60% GFR, 40% rice straw powder, pH 8.5 and 6 days at 26°C. A total of 371g housefly larvae meal and 2,064g digested residue were bio-converted from 3,500g raw GFR mixture contaning1, 400g rice straw in the unit of (calculated) dry matter. HFL meal derived from GFR contained 56.4% protein, 21.6% fat, and several essential amino acids, suggesting that it is a potential alternative animal feed protein source. Additionally, the digested GFR could be utilized as an organic fertilizer with a content of 3.2% total nitrogen, 2.0% inorganic phosphorus, 1.3% potassium and 91.5% organic matter. This novel GFR bio-conversion method can mitigate potential environmental pollution and recycle the waste resources.
    Full-text · Article · May 2015 · PLoS ONE
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    ABSTRACT: Based a genomic library constructed, a novel alkaline serine protease gene (Bvsp) (963 bp) was cloned from a marine bacterium Bacillus vallismortis, encoding 320 amino acid residue with a deduced molecular mass of 34.4 kDa. Amino acid sequence analysis found that Bvsp shared highest identity (72%) to a previously reported protease. The Bvsp enzyme showed the optimal activity at pH 6.5 and 54 °C, and was stable over pH 6-10 and 40-60 °C. The activity of the enzyme could be activated by metal ions such as Ca2+, Mg2+, Zn2+ and Ba2+, especially, in the presence of 30 mmol l−1 Ca2+, reaching 5100 U·mg−1, 13 fold that of the control. In addition, Bvsp could degrade directly on cross-linked fibrin at an activity of 3863 U·mg−1, it is not a plasminogen activator. Bvsp could also digest Aα- and Bβ-chains readily, but the γ-chain of fibrinogen slowly. Therefore Bvsp may have the potential to control cardiovascular diseases.
    No preview · Article · Apr 2015 · Journal of Molecular Catalysis B Enzymatic
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    Lin Chen · Junpeng Chen · Ashok Kumar · Ziduo Liu
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    ABSTRACT: Chitinase, an important enzyme in chitin-degrading, have extensive biophysiological functions and immense potential applications. Here, a chitinase gene pachi was cloned from Pseudomonas aeruginosa and overexpressed in E. coli (DE3). The structural analysis showed that chitinase pachi consists of catalytic domain (CHC), chitin binding domain (CBD) and both of these are linked by connective domain (FN3). In this study, Pachi displayed optimal activity at temperature 65°C and pH 6.5. To understand the structural and functional relationship of chitin-binding domain with catalytic domain, two mutants, CHA (without CBD) and CBD+FN3-pachi with additional CBD have been constructed. Though the results showed that the two mutants have similar characteristics with Pachi, it is interesting to note that the deficiency of CBD caused an increase in expression level as well as solubility of the CHA. Moreover, the catalytic efficiency of CHA was increased 1.26-fold and substrate affinity in the absence of CBD was decreased 1.85-fold. Thus, the improved solubility and activity of CHA by domain deficiency is an interesting pathway to study the relationship of structure and function of chitinase and support its potential use in commercial applications. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · Apr 2015 · International journal of biological macromolecules
  • Junjie Huang · Lin Chen · Nan Hu · Wei Jiang · Gaobing Wu · Ziduo Liu
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    ABSTRACT: The current L-serine production relies mainly on cellular or enzymatic conversion from the precursor glycine plus a C1 compound. To date, only several reports have been published on L-serine production from glycine and methanol by methylotrophic bacteria with the serine pathway. This work aimed to isolate a novel serine hydroxymethyltransferase (SHMT) from the methanol-using Arthrobacter sp. and use it for L-serine production with the enzymatic conversion method. Here, A novel glyA gene was isolated from the methanol-using Arthrobacter sp. by thermal asymmetric interlaced PCR (TAIL-PCR), encoding a serine hydroxymethyltransferase (SHMT) with 440 amino acids, belonging to the α-family of fold type I, and pyridoxal-5-phosphate (PLP) dependent enzymes. The enzyme was stable in weakly alkali conditions, showing the optimal activity at pH 7.8 and 45 °C, and a 2.75-fold increase in activity over the corresponding enzyme of Escherichia coli. Two methods (resting cells reaction and enzymatic conversion) were employed to produce serine. Using glycine (133 mM) and formaldehyde (13.3 mM) as substrates to produce serine by enzymatic reaction, 93.6 mM L-serine was obtained with a 70.4 % molar conversion rate from glycine to L-serine. Thus, the characteristics of this novel strain and its enzyme suggest that it has the potential for further research and industrial use.
    No preview · Article · Jan 2015 · Annals of Microbiology
  • Gaobing Wu · Yongjun Qin · Qipeng Cheng · Ziduo Liu
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    ABSTRACT: A novel gene (amyZ2) encoding an alkali-stable and salt-tolerant α-amylase from marine bacteriumZunongwangia profunda (MCCC 1A01486) was cloned and expressed in Escherichia coli. The gene (1446 bp)encodes a polypeptide with a predicted N-terminal signal peptide consisting of 24 amino acids and amature α-amylase of 457 amino acids (AmyZ2). The estimated molecular mass of AmyZ2 was 50 kDaby SDS-PAGE. AmyZ2 belongs to glycoside hydrolase family 13 and shares the highest identity (45%)with the characterized α-amylase from Pyrocoocus woesei (PDB id: 1MWO). The purified enzyme showedthe maximum activity at 50°C, pH 7.0, and retained approximately 143 and 126% initial activity after 5days of incubation (25°C) at pH 10.0 and 11.0, respectively, indicating its alkali stability. In addition, ithad a salinity-tolerance range of 05 M NaCl with a salt optimum at 2 M (138% initial activity), retainingmore than 130% initial activity at 0.52.5 M and about 100% activity at 3.5 M NaCl. AmyZ2 was relativelystable in 04 M NaCl and its thermostability was significantly improved by the pre-incubation of enzymesolution with 2 M NaCl at 50°C for 3 h, which led to a 53.6-fold increase in the residual activity. The Km and kcat values of AmyZ2 were 11.71 mg ml?1and 1449.43 s?1, and the catalytic efficiency (kcat/Km) was123.78 ml mg?1s?1. AmyZ2 exhibited a specific activity of 1662.4 U/mg toward soluble starch. The salt-tolerance and extreme alkali-stability of AmyZ2 suggests its potential applications in harsh industrialprocesses.
    No preview · Article · Dec 2014 · Journal of Molecular Catalysis B Enzymatic
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    Wei Jiang · Lin Chen · Shaohui Yuan · Bin Li · Ziduo Liu
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    ABSTRACT: Background Serine hydroxymethyltransferase (SHMT) is the key enzyme in L-serine enzymatic production, suggesting the importance of obtaining a SHMT with high activity.ResultsHere, a novel SHMT gene, glyA, was obtained through degenerate oligonucleotide-primed PCR and encoded a novel SHMT with 54.3% similarity to the known SHMT from Escherichia coli. The obtained protein AnSHMT showed the optimal activity at 40°C and pH 7.5, and was more stable in weakly alkali conditions (pH 6.5-8.5) than Hyphomicrobium methylovorum¿s SHMT (pH 6.0-7.5), In order to improve the catalytic efficiency of the wild type, the site-directed mutagenesis based on sequences alignment and bioinformatics prediction, was used and the catalytic efficiency of the mutant I249L was found to be 2.78-fold higher than that of the wild-type, with the replacement of isoleucine by leucine at the 249 position.Conclusions This research provides useful information about the interesting site, and the application of DOP-PCR in cloning a novel glyA gene.
    Preview · Article · Nov 2014 · BMC Biotechnology
  • Shaohui Yuan · Wei Jiang · Lin Chen · Yiming Guo · Ziduo Liu
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    ABSTRACT: A novel glyA gene from the marine bacterium Alcanivorax sp. was cloned and expressed in Escherichia coli BL21 (DE3). The recombinant glyA encodes a polypeptide of 418 amino acids, which was designated as AdSHMT that shows the highest identity (70%) with a SHMT from Shewanella algae. The purified enzyme showed a single band at about 45 kDa by SDS-PAGE analysis. It was found that AdSHMT exhibited the maximal activity at 50 °C and pH 7.0. The Km, Vmax, and Kcat values of AdSHMT against dl-threo-3-phenylserine were calculated to be 0.097 mol/L, 3.255 μmol/min/mg and 2.451/s, respectively. More importantly, RP-HPLC detection showed that the AdSHMT achieved an 88.37% molecular conversion rate in catalyzing glycine to l-serine, with the final concentration of l-serine being 353.15 mM in the reaction at 35 °C and 22nd hour when the initial concentration of the substrate (glycine) was 0.399 M. The molecular conversion rate of the AdSHMT from the Alcanivorax sp. was 1.26-fold that of the EcSHMT from the E. coli, which is currently applied in industrial production. Therefore, AdSHMT has the potential for industrial applications due to its high enzymatic conversion rate.
    No preview · Article · Nov 2014 · Journal of Molecular Catalysis B Enzymatic
  • Shanshan Zhang · Gaobing Wu · Shiyu Feng · Ziduo Liu
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    ABSTRACT: A 1.020-bp esterase gene, estQ, encoding for a protein of 339 amino acids, was cloned from Aspergillus fumigatus and expressed in E. coli. EstQ exhibited the optimal activity around 40°C and pH 9.0. In order to obtain more thermostable esterases, three mutants (A134T, V160T, A134T-V160T) were constructed by site-directed mutagenesis and also characterized for further research. Compared to A134T and V160T displaying their optimum activity at 40°C, A134T-V160T exhibited a 5°C higher optimal temperature and a longer half-life more than 24 times than that of WT at 50°C. All the mutants displayed favorable effects on thermostability and retained 53-76% activity after pre-incubation for 30min at 45°C, about 20-40% higher than that of the WT. With an increase in Km of the three mutants, a decrease in catalytic efficiency in kcat/Km was observed in mutant V160T and A134T-V160T against p-nitrophenyl butyrate. Homology models of WT and A134T-V160T were built to understand the structure-function relationship. The analysis results showed that the improved thermostability may be due to the favorable interaction and additional hydrogen bonds formed in the mutants by substitution of hydrophobic residues with hydrophilic residues. This study provide useful theoretical reference for enzyme evolution in vitro.
    No preview · Article · Oct 2014 · Enzyme and Microbial Technology
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    ABSTRACT: NS2 from influenza A virus mediates Crm1-dependent vRNP nuclear export through interaction with Crm1. However, even though the nuclear export signal 1 (NES1) of NS2 does not play a requisite role in NS2–Crm1 interaction, there is no doubt that NES1 is crucial for vRNP nuclear export. While the mechanism of the NES1 is still unclear, it is speculated that certain host partners might mediate the NES1 function through their interaction with NES1. In the present study, chromodomain-helicase-DNA-binding protein 3 (CHD3) was identified as a novel host nuclear protein for locating NS2 and Crm1 on dense chromatin for NS2 and Crm1-dependent vRNP nuclear export. CHD3 was confirmed to interact with NES1 in NS2, and a disruption to this interaction by mutation in NES1 significantly delayed viral vRNPs export and viral propagation. Further, the knockdown of CHD3 would affect the propagation of the wild-type virus but not the mutant with the weakened NS2–CHD3 interaction. Therefore, this study demonstrates that NES1 is required for maximal binding of NS2 to CHD3, and that the NS2–CHD3 interaction on the dense chromatin contributed to the NS2-mediated vRNP nuclear export. Electronic supplementary material The online version of this article (doi:10.1007/s00018-014-1726-9) contains supplementary material, which is available to authorized users.
    Preview · Article · Sep 2014 · Cellular and Molecular Life Sciences CMLS
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    ABSTRACT: The 5-enolpyruvylshikimate - 3-phosphate synthase (EPSPS) is a key enzyme in the aromatic amino acid biosynthetic pathway in microorganisms and plants, which catalyzes the formation of 5-enolpyruvylshikimate-3-phosphate (EPSP) from shikimate-3-phosphate (S3P) and phosphoenolpyruvate (PEP). In this study, a novel AroA-encoding gene was identified from the deep sea bacterium Alcanivorax sp. L27 through screening the genomic library and termed as AroAA.sp. A phylogenetic analysis revealed that AroAA.sp (1,317 bp and 438 amino acids) is a class II AroA. This enzyme exhibited considerable activity between pH 5.5 and pH 8.0 and notable activity at low temperatures. The KM for PEP and IC50 [glyphosate] values (the concentration of glyphosate that inhibited enzyme activity by 50%) of AroAA.sp were 78 μM and 1.5 mM, respectively. Furthermore, site-directed mutagenesis revealed that the G100A mutant had a 30-fold increase in the IC50 [glyphosate] value; while the L105P mutant showed only 20% catalytic activity compared to wild-type AroAA.sp. The specific activity of the wild-type AroAA.sp, the G100A mutant and the L105P mutant were 7.78 U/mg, 7.26 U/mg and 1.76 U/mg, respectively. This is the first report showing that the G100A mutant of AroA displays considerably improved glyphosate resistance and demonstrates that Leu105 is essential for the enzyme's activity.
    No preview · Article · Sep 2014 · Enzyme and Microbial Technology
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    Sen Yang · Qing Li · Yang Gao · Longyu Zheng · Ziduo Liu
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    ABSTRACT: Although biodiesel is a sustainable and renewable diesel fuel, the current feedstock predominantly from edible oils limits the economic feasibility of biodiesel production and thus the development of a cost-effective non-food feedstock is really essential. In this study, approximately 21.6% of crude grease was extracted from housefly (Musca domestica L.) larvae reared on swine manure, and the extracted grease was evaluated for biodiesel production concerning the variables affecting the yield of acid-catalyzed production of methyl esters and the properties of the housefly larvae-based biodiesel. The optimized process of 8:1 methanol/grease (mol/mol) with 2 vol% H2SO4 reacted at 70 °C for 2 h resulted in a 95.7% conversion rate from free fatty acid (FFA) into methyl esters. A 90.3% conversion rate of triglycerides (crude grease) to its esters was obtained from alkaline trans-esterification using sodium hydroxide as catalyst. The major fatty acid components of this larvae grease were palmitic (29.1%), oleic (23.3%), palmitoletic (17.4%) and linoleic (17.2%). The housefly larvae-based biodiesel has reached the ASTM D6751-10 standard in density (881 kg/m3), viscosity (5.64 mm2/s), ester content (96.8%), flash point (145 °C), and cetane number (52). These findings suggest that the grease derived from swine manure-grown housefly larvae can be a feasible non-food feedstock for biodiesel production.
    Full-text · Article · Jun 2014 · Renewable Energy
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    ABSTRACT: Phosphinothricin (PPT) is a kind of non-selective, environmentally friendly herbicide. PPT-tolerance genes are vital in both plant biotechnology as selectable markers and the development of transgenic herbicide-resistant crops. However, there are no other well-identified and commercially available PPT-resistance genes for use in plant genetic engineering besides two PPT N-acetyltransferase genes, which known as pat and bar derived from Streptomyces sp. Here, we isolated a novel PPT N-acetyltransferase gene from PPT-resistant marine bacteria, Rhodococcus sp. strain YM12. The gene, designated as RePAT, encoded a protein (RePAT) of 162 amino acids, which showed 37% identity with that of PAT proteins. Key kinetic constants of RePAT were determined (Km = 0.076 mM, Kcat= 131 min−1) using PPT as a substrate, the enzyme retained considerable activity at pH 8.0 and had an optimum temperature of 35 °C. Interestingly, it possessed over 50% of its maximal activity at temperature conditions between 0 and 10 °C, suggesting that this enzyme is able to protect crop against PPT injury in cold environment. These results illustrated that RePAT could be a new resource for herbicide detoxification by transgenic crops.
    No preview · Article · Jun 2014 · Journal of Molecular Catalysis B Enzymatic
  • Lu Li · Jiawen Zhu · Kui Yang · Zhuofei Xu · Ziduo Liu · Rui Zhou
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    ABSTRACT: Actinobacillus pleuropneumoniae is an important porcine respiratory pathogen causing great economic losses in the pig industry worldwide. Oxygen deprivation is a stress that A. pleuropneumoniae will encounter during both early infection and the later, persistent stage. To understand modulation of A. pleuropneumoniae gene expression in response to the stress caused by anaerobic conditions, gene expression profiles under anaerobic and aerobic conditions were compared in this study. The microarray results showed that 631 genes (27.7% of the total ORFs) were differentially expressed in anaerobic conditions. Many genes encoding proteins involved in glycolysis, carbon source uptake systems, pyruvate metabolism, fermentation and the electron respiration transport chain were up-regulated. These changes led to an increased amount of pyruvate, lactate, ethanol and acetate in the bacterial cells as confirmed by metabolite detection. Genes encoding proteins involved in cell surface structures, especially biofilm formation, peptidoglycan biosynthesis and lipopolysaccharide biosynthesis were up-regulated as well. Biofilm formation was significantly enhanced under anaerobic conditions. These results indicate that induction of central metabolism is important for basic survival of A. pleuropneumoniae after a shift to an anaerobic environment. Enhanced biofilm formation may contribute to the persistence of this pathogen in the damaged anaerobic host tissue and also in the early colonization stage. These discoveries give new insights into adaptation mechanisms of A. pleuropneumoniae in response to environmental stress.
    No preview · Article · Apr 2014 · The Journal of Microbiology