Isolation of Secondary Metabolites with Antimicrobial Activities from Bacillus amyloliquefaciens LWYZ003

The strain LWYZ003, which can restrain multiple pathogens, was screened from the sediment of the ocean and identified as Bacillus amyloliquefaciens. Large-scale fermentation and modern chromatographic separation technologies(macroporous resin column chromatography, silica gel column chromatography, thin-layer chromatography and high-performance liquid chromatography) were used to separate antimicrobial products from the fermentation broth of marine-derived Bacillus amyloliquefaciens LWYZ003. Bioactive-guided separation was used in the term of seeking antimicrobial products from the secondary metabolites of Bacillus amyloliquefaciens LWYZ003. As a result, two natural products cycloheximide( 1) and trehalose( 2) were obtained. Their structures were elucidated by Fourier transform infrared spectroscopy, high-resolution mass spectrometry, ~1 H and ^(13) C nuclear magnetic resonance analysis. In the cylinder plate method, compound 1 exhibited stronger antimicrobial activities than compound 2 against Micrococcus luteus, and also exhibited wider antimicrobial spectrum than compound 2. In conclusion, isolation of bioactive secondary metabolites from marine Bacillus sp. has enormous potentials in finding suitable antibiotics to inhibit multiple pathogens.

Computational fluid dynamics simulation of a novel bioreactor forsophorolipid production

This paper describes three-dimensional computational fluid dynamics(CFD) simulations of gas–liquid flow in a novel laboratory-scale bioreactor contained dual ventilation-pipe and double sieve-plate bioreactor(DVDSB)used for sophorolipid(SL) production. To evaluate the role of hydrodynamics in reactor design, the comparisons between conventional fed-batch fermenter and DVDSB on the hydrodynamic behavior are predicted by the CFD methods. Important hydrodynamic parameters of the gas–liquid two-phase system such as the liquid phase velocity field, turbulent kinetic energy and volume-averaged overall and time-averaged local gas holdups were simulated and analyzed in detail. The numerical results were also validated by experimental measurements of overall gas holdups. The yield of sophorolipids was significantly improved to 484 g·L^(-1)with a 320 h fermentation period in the new reactor.

Engineering Corynebacterium glutamicum for Geraniol Production

Geraniol is a monoterpenoid alcohol with various applications in food,cosmetics,and healthcare.Corynebacterium glutamicum is a potential platform for terpenoids production because it harbors the methylerythritol phosphate pathway.To engineer C.glutamicum to produce geraniol,two different truncated geraniol synthases (GESs) were respectively expressed,and strain LX02 expressing the truncated GESs from Valeriana officinalis (t Vo GES) produced 0.3 mg/L of geraniol.Then,three geranyl diphosphate synthases (GPPSs) were combinatorially co-expressed with t Vo GES to improve geraniol production.The amounts of produced geraniol were all higher than that produced by strain LX02.Strain LX03 co-expressing ERG20 F96W–N127W (ERG20 WW) and t Vo GES produced the highest amount,5.4 mg/L.Subsequently,the co-overexpression of1-deoxy-D-xylulose-5-phosphate synthase (dxs) and isopentenyl diphosphate isomerase (idi) further increased the production to 12.2 mg/L in strain LX03.Lastly,the production of geraniol was increased to 15.2 mg/L via fermentation optimization.To our knowledge,this is the first report on the engineering of C.glutamicum to produce geraniol and thus can serve as a reference for other monoterpenoid production studies.

Characterization and analysis of petrochemical wastewater through particle size distribution, biodegradability, and chemical composition

The centralized treatment method is a widely used form of wastewater treatment that tends to be less effective at removing toxic substances. Therefore, a detailed analysis of the composition of wastewater can provide important information for the design of an effective wastewater treatment process. The objective of this paper was to investigate particle size distribution(PSD), biodegradability, and the chemical composition of the petrochemical wastewater discharges. For this purpose, this project selected the petrochemical wastewater and treated wastewater of China National Offshore Oil Corporation Zhongjie Petrochemical Co, Ltd. as the analysis objects.The step-by-step filtration method, along with a molecular weight classification method, was selected to build the chemical oxygen demand(COD) and biochemical oxygen demand(BOD) fingerprints of petrochemical wastewater and treated wastewater. The results showed that the main pollutants were settleable particles in petrochemical wastewater, which contributed to over 54.85% of the total COD. The colloidal particles with particle sizes in the range of 450–1000 nm had the highest COD value in the treated wastewater, which contributed34.17% of the total COD of treated wastewater. The results of the BOD analysis showed that the soluble fractions were the main reason that treated wastewaters did not meet the treatment standards. Tests on the organic compounds in petrochemical wastewater found that there were mainly linear paraffins, branched paraffins, benzene series compounds, and some plasticizers in the influent of the petrochemical wastewater. The most abundant pollutants in treated petrochemical wastewater were the adjacent diisobutyl phthalate and the linear alkanes.Fourier transform infrared(FTIR) transmission spectroscopy analysis showed that the settleable particles of petrochemical wastewater and membrane bioreactor(MBR)-treated wastewater contained multiple types of organic substances. The results also indicated that removing the oil-settleable substances, the colloidal particles(450–1000 nm), and the soluble organics will be necessary for the treatment of petrochemical wastewater.

n-Hexadecane and pyrene biodegradation and metabolization by Rhodococcus sp. T1 isolated from oil contaminated soil

The high-molecular weight polycyclic aromatic hydrocarbons(PAHs) pyrene and typical long chain alkane nhexadecane are both difficult to degrade. In this study, n-hexadecane and pyrene degrading strain Rhodococcus sp. T1 was isolated from oil contaminated soil. Strain T1 could remove 90.81% n-hexadecane(2 vol%) and 42.79% pyrene(200 mg·L^(-1)) as a single carbon within 5 days, respectively. Comparatively, the degradation of pyrene increased to 60.63%, but the degradation of n-hexadecane decreased to 87.55% when these compounds were mixed. Additionally, identification and analysis of degradation metabolites of Rhodococcus sp. T1 in the above experiments showed that there were significant changes in alanine, methylamine, citric acid and heptadecanoic acid between sole and dual substrate degradation. The optimal conditions for degradation were then determined based on analysis of the pH, salinity, additional nutrient sources and liquid surface activity.Under the optimal conditions of pH 7.0, 35 °C, 0.5% NaCl, 5 mg·L^(-1) of yeast extract and 90 mg·L^(-1) of surfactant,the degradation increased in single or dual carbon sources. To our knowledge, this is the first study to discuss metabolite changes in Rhodococcus sp. T1 using sole substrate and dual substrate to enhance the long-chain alkanes and PAHs degradation potential.

The Combinatorial Biosynthesis of＂Unnatural＂ Products with Polyketides

Polyketides have been widely used clinically due to their significant biological activities, but the needed structural and functional diversity cannot be achieved by common chemical synthetic methods. The tool of combinatorial biosynthesis provides the possibility to produce "unnatural" natural drugs, which has achieved initial success. This paper provides an overview for the strategies of combinatorial biosynthesis in producing the structural and functional diversity of polyketides, including the redesign of metabolic flow, polyketide synthase(PKS) engineering, and PKS post-translational modification. Although encouraging progress has been made in the last decade, challenges still exist regarding the rational combinatorial biosynthesis of polyketides. In this review, the perspectives of polyketide combinatorial biosynthesis are also discussed.

Fed-Batch Fermentation for Spinosad Production in an Improved Reactor

As a kind of aerobic bacteria, Saccharopolyspora spinosa exhibits a high demand for oxygen. In the fermentation process, the methods of increasing ventilation and improving agitation speed are usually adopted to achieve higher values of dissolved oxygen. These methods decrease the efficiency of spinosad biosynthesis. In this study, an improved reactor was designed to solve these problems. The exhaust gas reflux device, impellers, and baffles were improved. Furthermore, we established the kinetic models for the cell growth, substrate consumption and spinosad generation in batch fermentation process. The simulation results were in good agreement with the experimental data. Spinosad production reached 583.86 mg/L after employing the suitable feeding strategy by fed-batch fermentation in the improved reactor, whereas it was only 157.01 mg/L before optimization. The method described can provide insight to strengthen spinosad production and can be extended to the culturing process of filamentous aerobic bacteria. © 2017 Tianjin University and Springer-Verlag Berlin Heidelberg

Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient(0-0.4043 g/g)in surface(5-10 cm)and subsurface(35-40 cm)petroleum-contaminated soil samples from the Dagang Oilfield,China.Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods,the bacterial diversity of the soil was studied.Subsequently,the environmental parameters were measured to analyze its relationship with the community variation.Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils,but no differences were observed in different depths of petroleum-contaminated soil.Meanwhile,many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties.Total petroleum hydrocarbon,total organic carbon,and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils.Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Research of 1,3-Dihydroxyacetone Production by Overexpressing Glycerol Transporter and Glycerol Dehydrogenase

1,3-Dihydroxyacetone (DHA), a natural ketose, is widely used in the chemical, cosmetic, and pharmaceutical industries. The current method for DHA production is Gluconobacter oxydans ( G. oxydans ) fermentation, but the high concentration of glycerol in the fermentation broth inhibits cells growth. To overcome this obstacle, in this study, we overexpressed the glycerol transporter (GlpFp) by the use of promoters P tufB , P gmr , P glp1 , and P glp2 in G. oxydans 621H. The results show that the glycerol tolerances of strains overexpressing G lpF were all much better than that of the control strain. The glycerol dehydrogenase gene (G dh) was overexpressed by the promoters P tufB and P gdh , which increased the DHA titer by 12.7% compared with that of the control group. When G lpF and Gdh genes were co-overexpressed in G. oxydans 621H, the OD600 value of the engineered strains all increased, but the DHA titers decreased in di erent degrees, as compared with strains that overexpressed only G dh . This study provides a reference for future research on DHA production.

OsBLS6.2:A rice bacterial leaf streak resistance gene identified by GWAS and RNA-seq

Bacterial leaf streak(BLS),caused by Xanthomonas oryzae pv.oryzicola(Xoc),is a bacterial disease affecting rice production in Asia and Africa,whose severity is expected to increase with climate change.Identification of new quantitative-trait loci(QTL)or resistance genes for BLS resistance is essential for developing resistant rice.A genome-wide association study to identify QTL associated with BLS resistance was conducted using phenotypic and genotypic data from 429 rice accessions.Of 47 QTL identified,45 were novel and two co-localized with previously reported QTL or genes conferring BLS resistance.qBLS6.2 on chromosome 6 explained the greatest phenotypic variation.Combined analysis of differential expression and annotations of predicted genes near qBLS6.2 based on haplotype and disease phenotype identified OsBLS6.2(LOC_Os06g02960)as a candidate gene for qBLS6.2.OsBLS6.2 knockout plants showed higher resistance to Xoc than wild-type plants.Many other candidate genes for resistance to Xoc were identified.

Molecular Simulation and Catalytic Active Sites Identification of Dammarenediol-Ⅱ Synthase

Squalene and oxidosqualene cyclizations are regarded as the most complex chemical reactions in the nature,which can achieve protonation,deprotonation,a sequence of hydride and methyl migration. Dammarenediol-Ⅱ synthase（ DS）,as a kind of 2,3-oxidosqualene-triterpene cyclase,catalyses2,3-oxidosqualene to form dammarenediol-Ⅱ. To assess the three-dimensional（ 3 D） structure and catalytic active sites of dammarenediol-Ⅱ synthase,utilizing the homology modeling method,3 D models of DS were established in the Modeller9 v14 software and I-TASSER server. With the highest sequence identity with DS,human oxidosqualene cyclase 3 D models（ PDB： 1 W6K and 1 W6J） were chosen as templates. Through further evaluation and optimization,an optimal DS model was obtained consequently. Then several putative catalytic active sites were found through the molecular docking simulation between DS model and product dammarenediol-Ⅱ by using Autodock 4. 2. Finally,site-directed mutants of DS were expressed in Saccharomyces cerevisiae,a significant decrease of the yield of dammarenediol-Ⅱ is achieved,which verified the significance of these putative active sites.

Phase transition of multi-component(TiZrVNb)C ceramics—Part II:From single phase to multiple phases via adjusting V content

To address the relatively mediocre mechanical properties of single-phase multi-component carbide ceramics,a phase transition from a single phase to multiple phases was proposed to achieve superior mechanical properties.A series of(TiZrV_(x)Nb)C_(0.8) ceramics with different V contents were fabricated by spark plasma sintering(SPS).The influence of the V content on the phase composition,microstructural evolution,and mechanical properties was investigated in detail.The transition behavior from a single phase to multiple phases is discovered and discussed.The formation of the Zr-rich phase and Zr-poor phase can be attributed to the increase in lattice distortion and mixed enthalpy caused by the addition of V.A nanometer lamellar structure with a semi-coherent interface obtained via in situ decomposition is reported for the first time in multi-component carbide ceramics.The semi-coherent interfaces with high dislocation density and strain concentration effectively improve the mechanical properties,grain refinement,and multi-phase formation.The optimal comprehensive mechanical properties of the Vickers hardness(26.3 GPa),flexural strength(369 MPa),and fracture toughness(3.1 MPa·m^(1/2))were achieved for the sample with 20 mol%V.

Phase transition of multi-component(TiZrVNb)C ceramics—Part I:Phase decomposition induced by carbon content

Phase decomposition can effectively enhance the mechanical properties of carbide ceramics and can overcome the difficulty of enhancing the mechanical properties of single-phase multicomponent carbide ceramics.In this work,a series of nonstoichiometric(TiZrVNb)Cx ceramics were prepared by spark plasma sintering(SPS)at different temperatures.The effects of the carbon content on the phase composition,microstructure evolution,and mechanical properties were investigated in detail.Phase decomposition occurred with decreasing carbon content.Two different solid solutions of(Ti,V)-rich and Zr-rich phases formed from the decomposition of equimolar single-phase solid solutions,namely,the Zr-poor phase and Zr-rich phase,respectively.The distribution of Nb element is relatively uniform.The semicoherent interfaces between the Zr-poor phase and the Zr-rich phase can harden and strengthen effectively under the synergistic effect of grain refinement.Ceramics with phase decomposition structures have apparent advantages compared to single-phase high-entropy carbides.This work provides an important train of thought for the microstructure tailoring and properties optimization of multi-component carbide ceramics.

Densification,microstructure and mechanical properties of multicomponent(TiZrHfNbTaMo)C ceramic prepared by pressureless sintering

A multicomponent(TiZrHfNbTaMo)C ceramic has been fabricated by pressureless sintering at temperatures from 2100℃to 2500℃,using an equimolar multicomponent carbide powder synthesized by carbothermal reduction as the starting material.Influence of sintering temperature on densification,microstructure and mechanical properties of the ceramics was investigated.The relative density increases with increasing sintering temperature,and a nearly fully dense sample is achieved by pressureless sintering at 2500℃.Average grain size increases from 3.7 to 15.2μm with increasing sintering temperature from 2300 to 2500℃.The(TiZrHfNbTaMo)C ceramic sintered at 2400℃exhibits a single phase fcc structure with homogeneous chemical composition,an average grain size of 7.0μm and a relative density of96.5%,while its measured hardness is 33.2 GPa at 100 mN and 23.2 GPa at 9.8 N.

Low thermal conductivity of dense(TiZrHfVNbTa)C_(x) high-entropy carbides by tailoring carbon stoichiometry

Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a major obstacle to its application in an ultra-high-temperature insulation system.In this work,the low thermal conductivity of dense(TiZrHfVNbTa)Cx(x=0.6-1)high-entropy carbides has been realized by adjusting the carbon stoichiometry.The thermal conductivity gradually decreases from 10.6 W·m^(−1)·K^(−1) at room temperature to 6.4 W·m^(−1)·K^(−1) with carbon vacancies increasing.Due to enhanced scattering of phonons and electrons by the carbon vacancies,nearly full-dense(97.9%)(TiZrHfVNbTa)C_(0.6) possesses low thermal conductivity of 6.4 W·m^(−1)·K^(−1),thermal diffusivity of 2.3 mm^(2)·s^(−1),as well as electrical resistivity of 165.5μΩ·cm.The thermal conductivity of(TiZrHfVNbTa)C_(0.6) is lower than that of other quaternary and quinary high-entropy carbide ceramics,even if taking the difference of porosity into account in some cases,which is mainly attributed to compositional complexity and carbon vacancies.This provides a promising route to reduce the thermal conductivity of high-entropy carbides by increasing the number of metallic elements and carbon vacancies.