Ziduo Liu

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

Are you Ziduo Liu?

Claim your profile

Publications (61)165.74 Total impact

  • [Show abstract] [Hide abstract]
    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.
    International journal of biological macromolecules 07/2015; DOI:10.1016/j.ijbiomac.2015.07.045 · 3.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    International Journal of Biological Macromolecules 05/2015; 79. DOI:10.1016/j.ijbiomac.2015.05.030 · 3.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    PLoS ONE 05/2015; 10(5):e0110809. DOI:10.1371/journal.pone.0110809 · 3.23 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Journal of Molecular Catalysis B Enzymatic 04/2015; 117. DOI:10.1016/j.molcatb.2015.04.006 · 2.75 Impact Factor
  • Source
    Lin Chen · Junpeng Chen · Ashok Kumar · Ziduo Liu
    [Show abstract] [Hide abstract]
    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.
    International journal of biological macromolecules 04/2015; 78. DOI:10.1016/j.ijbiomac.2015.04.017 · 3.10 Impact Factor
  • Junjie Huang · Lin Chen · Nan Hu · Wei Jiang · Gaobing Wu · Ziduo Liu
    [Show abstract] [Hide abstract]
    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.
    Annals of Microbiology 01/2015; 65(3). DOI:10.1007/s13213-014-1008-7 · 1.04 Impact Factor
  • Gaobing Wu · Yongjun Qin · Qipeng Cheng · Ziduo Liu
    Journal of Molecular Catalysis B Enzymatic 12/2014; 110. DOI:10.1016/j.molcatb.2014.08.023 · 2.75 Impact Factor
  • Source
    Wei Jiang · Lin Chen · Shaohui Yuan · Bin Li · Ziduo Liu
    [Show abstract] [Hide abstract]
    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.
    BMC Biotechnology 11/2014; 14(1):93. DOI:10.1186/s12896-014-0093-9 · 2.59 Impact Factor
  • Shaohui Yuan · Wei Jiang · Lin Chen · Yiming Guo · Ziduo Liu
    [Show abstract] [Hide abstract]
    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.
    Journal of Molecular Catalysis B Enzymatic 11/2014; 109:17-23. DOI:10.1016/j.molcatb.2014.07.013 · 2.75 Impact Factor
  • Shanshan Zhang · Gaobing Wu · Shiyu Feng · Ziduo Liu
    [Show abstract] [Hide abstract]
    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.
    Enzyme and Microbial Technology 10/2014; 64-65:11-6. DOI:10.1016/j.enzmictec.2014.06.003 · 2.97 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Cellular and Molecular Life Sciences CMLS 09/2014; 72(5). DOI:10.1007/s00018-014-1726-9 · 5.86 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Enzyme and Microbial Technology 09/2014; DOI:10.1016/j.enzmictec.2014.02.010 · 2.97 Impact Factor
  • Source
    Sen Yang · Qing Li · Yang Gao · Longyu Zheng · Ziduo Liu
    [Show abstract] [Hide abstract]
    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.
    Renewable Energy 06/2014; 66:222–227. DOI:10.1016/j.renene.2013.11.076 · 3.36 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Journal of Molecular Catalysis B Enzymatic 06/2014; 104. DOI:10.1016/j.molcatb.2014.03.001 · 2.75 Impact Factor
  • Lu Li · Jiawen Zhu · Kui Yang · Zhuofei Xu · Ziduo Liu · Rui Zhou
    [Show abstract] [Hide abstract]
    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.
    The Journal of Microbiology 04/2014; 52(6). DOI:10.1007/s12275-014-3456-y · 1.53 Impact Factor
  • Haibo Xu · Yongjun Qin · Zongqing Huang · Ziduo Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel gene (BmelA) (1323 bp) encoding an α-galactosidase of 440 amino acids was cloned from the deep-sea bacterium Bacillus megaterium and the protein was expressed in Escherichia coli BL21 (DE3) with an estimated molecular mass of about 45 kDa by SDS-PAGE. The enzyme belongs to glycoside hydrolase family 4, with the highest identity (74%) to α-galactosidase Mel4A from Bacillus halodurans among the characterized α-galactosidases. The recombinant BmelA displayed its maximum activity at 35 °C and pH 8.5-9.0 in 50 mM Tris-HCl buffer, and could hydrolyze different substrates with the Km values against p-nitrophenyl-α-D-galactopyranoside (pNP-α-Gal), raffinose and stachyose being 1.02 ± 0.02, 2.24 ± 0.11 and 3.42 ± 0.17 mM, respectively. Besides, 4 mutants (I38 V, I38A, I38F and Q84A) were obtained by site-directed mutagenesis based on molecular modeling and sequence alignment. The kinetic analysis indicated that mutants I38 V and I38A exhibited a 1.7- and 1.4-fold increase over the wild type enzyme in catalytic efficiency (kcat/Km) against pNP-α-Gal, respectively, while mutant I38F showed a 3.5-fold decrease against pNP-α-Gal and mutant Q84A almost completely lost its activity. All the results suggest that I38 and Q84 sites play a vital role in enzyme activity probably due to their steric and polar effects on the predicted “tunnel” structure and NAD+ binding to the enzyme.
    Enzyme and Microbial Technology 03/2014; 56. DOI:10.1016/j.enzmictec.2014.01.004 · 2.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new xylanase gene (xynA) from the marine microorganism Zunongwangia profunda was identified to encode 374 amino acid residues. Its product (XynA) showed the highest identity (42.78 %) with a xylanase from Bacillus sp. SN5 among the characterized xylanases. XynA exhibited the highest activity at pH 6.5 and 30 °C, retaining 23 and 38 % of the optimal activity at 0 and 5 °C, respectively. XynA was not only cold active, but also halophilic, and both its activity and thermostability could be significantly increased by NaCl, showing the highest activity (180 % of the activity) at 3 M NaCl and retaining nearly 100 % activity at 5 M NaCl, compared to the absence of NaCl. In the presence of 3 M NaCl, the k cat/K m value of XynA exhibited a 3.41-fold increase for beechwood xylan compared to no added NaCl, and the residual activity of XynA increased from 23 % (no added NaCl) to 58 % after 1 h incubation at 45 °C. This may be the first report concerning a cold-adapted xylanase from a non-halophilic species that displays the highest activity at a NaCl concentration range from 3 to 5 M. The features of cold activity and salt tolerance suggest the potential application of XynA in the food industry and bioethanol production from marine seaweeds.
    Extremophiles 01/2014; 18(2). DOI:10.1007/s00792-014-0629-x · 2.17 Impact Factor
  • Sen Yang · Ziduo Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: Swine manure may cause environmental pollution and resource waste if not handled properly on pig farms. In this paper, the technology for pig manure biodegradation and biodiesel production using Chrysomya megacephala (Fabricius) is described. About 700 kg of fresh pig manure (73% moisture) can be converted within one week into 18.2 kg dried larvae biomass containing about 21.11% oil in a pilot plant. The properties of the oil extracted from the larvae meal treated with three different drying methods were compared, indicating that the drying method may affect the properties of feedstock oil. The acid value (1.9 mg KOH/g), iodine value (86.3 gI/100 g), melt point (3.1 °C) and peroxide value (0.08 meq/kg) of the oil extracted from the larvae treated with both boiling water and oven-drying were superior to the values of the larvae treated with either oven-drying or sun-drying directly. The main fatty acids of the swine manure C. megacephala larvae oil were found to be composed of palmitic acid (36.91%), oleic acid (27.67%), palmitoleic acid (10.89%) and linoleic acid (9.49%). Most of the properties of the biodiesel converted from the feedstock oil by alkaline-catalyst transesterification met the EN 14214 standard in terms of density (0.89 g/cm3), viscosity (5.1 mm2/s), ester content (96.6%), flash point (138 °C), cetane number (56), water content (0.02%) and acid value (0.28 mg KOH/g). This study suggests that the swine manure-grown C. megacephala larvae could be a feasible feedstock for a large-scale biodiesel production.
    Applied Energy 01/2014; 113:385-391. DOI:10.1016/j.apenergy.2013.07.056 · 5.61 Impact Factor
  • Yongjun Qin · Zongqing Huang · Ziduo Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel gene (amyZ) encoding a cold-active and salt-tolerant α-amylase (AmyZ) was cloned from marine bacterium Zunongwangia profunda (MCCC 1A01486) and the protein was expressed in Escherichia coli. The gene has a length of 1785 bp and encodes an α-amylase of 594 amino acids with an estimated molecular mass of 66 kDa by SDS-PAGE. The enzyme belongs to glycoside hydrolase family 13 and shows the highest identity (25 %) to the characterized α-amylase TVA II from thermoactinomyces vulgaris R-47. The recombinant α-amylase showed the maximum activity at 35 °C and pH 7.0, and retained about 39 % activity at 0 °C. AmyZ displayed extreme salt tolerance, with the highest activity at 1.5 M NaCl and 93 % activity even at 4 M NaCl. The catalytic efficiency (k cat/K m) of AmyZ increased from 115.51 (with 0 M NaCl) to 143.30 ml mg(-1) s(-1) (with 1.5 M NaCl) at 35 °C and pH 7.0, using soluble starch as substrate. Besides, the thermostability of the enzyme was significantly improved in the presence of 1.5 M NaCl or 1 mM CaCl2. AmyZ is one of the very few α-amylases that tolerate both high salinity and low temperatures, making it a potential candidate for research in basic and applied biology.
    Extremophiles 12/2013; 18(2). DOI:10.1007/s00792-013-0614-9 · 2.17 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel esterase gene, estB, was cloned from the marine microorganism Alcanivorax dieselolei B-5(T) and overexpressed in E. coli DE3 (BL21). The expressed protein EstB with a predicted molecular weight of 45.1 kDa had a distinct catalytic triad (Ser(211)-Trp(353)-Gln(385)) and the classical consensus motif conserved in most lipases and esterases Gly(209)-X-Ser(211)-X-Gly(213). EstB showed very low similarity to any known proteins and displayed the highest similarity to the hypothetical protein (46 %) from Rhodococcus jostii RHA1. EstB showed the optimal activity around pH 8.5 and 20 °C and was identified to be extremely cold-adaptative retaining more than 95 % activity between 0 and 10 °C. The values of kinetic parameters on p-NP caproate (K m, K cat and K cat/K m) were 0.15 mM, 0.54 × 10(3) s(-1) and 3.6 × 10(3) s(-1) mM(-1), respectively. In addition, EstB showed remarkable stability in several studied organic solvents and detergents of high concentrations with the retention of more than 70 % activity after treatment for 30 min. The cold activity and its tolerance towards organic solvents made it a promising biocatalyst for industrial applications under extreme conditions.
    Extremophiles 12/2013; 18(2). DOI:10.1007/s00792-013-0612-y · 2.17 Impact Factor