[Objectives]The paper was to screen effective biocontrol strains against Meloidogyne incognita.[Methods]The effect of six bacterial strains sourced from the research group s strain library on the activity of second in...[Objectives]The paper was to screen effective biocontrol strains against Meloidogyne incognita.[Methods]The effect of six bacterial strains sourced from the research group s strain library on the activity of second instar larvae of M.incognita,as well as on egg hatching,was evaluated.[Results]The treatment of fermentation supernatant derived from the X-2 strain exhibited a pronounced lethal effect on M.incognita,with a corrected mortality rate reaching 97%within 72 h.Additionally,this treatment significantly inhibited egg hatching,achieving an inhibition rate of 94.69%at a 20-fold dilution.The strain was identified as Bacillus velezensis,belonging to the genus Bacillus,and was designated as RKN1111.[Conclusions]This study presents alternative strains and a theoretical framework for the biological control of M.incognita.展开更多
To investigate the characteristics of hydrogen production by a novel fermentative hydrogen-producing bacterial strain B49 (AF481148 in EMBL), batch experiments are conducted under different conditions. Hydrogen produc...To investigate the characteristics of hydrogen production by a novel fermentative hydrogen-producing bacterial strain B49 (AF481148 in EMBL), batch experiments are conducted under different conditions. Hydrogen production has a correlation with cell growth and the consumption of glucose and soluble protein. The optimum pH for cell growth is 4.5±0.15. At acidic pH 4.0±0.15, the bacteria has the maximum accumulated hydrogen volume of 2382 ml/L culture and the maximum hydrogen evolution rate of 339.9 ml/L culture·h with 1% glucose. The optimum temperature for cell growth and hydrogen production is 35℃. In addition, fermentative hydrogen-producing bacterial strain B49 can generate hydrogen from the decomposition of other organic substrates such as wheat, soybean, corn, and potato. Moreover, it can also produce hydrogen from molasses wastewater and brewage wastewater, and hydrogen yields are 137.9 ml H 2/g COD and 49.9 ml H 2/g COD, respectively.展开更多
Batch experiments were conducted to investigate the effects of magnesium on glucose metabolism, including growth and hydrogen-producing capacity of fermentative hydrogen-producing bacterial strain B49. These abilities...Batch experiments were conducted to investigate the effects of magnesium on glucose metabolism, including growth and hydrogen-producing capacity of fermentative hydrogen-producing bacterial strain B49. These abilities were enhanced with an increase in magnesium concentration. At the end of fermentation from （10 g/L） glucose, for 10 mg/L MgCl2·6H2O the cell growth in terms of optical density （OD） at 600nm was 0.46, the ratio of ethanol amount （mg/L） to acetate amount （mg/L） was 1.1, and the accumulated hydrogen volume was 934.9 mL H2/L culture; for 200 mg/L of MgCl2·6H2O OD600 nm was increased to 1.34. The accumulated hydrogen volume was increased to 2 360.5 mL H2/L culture, the ratio of ethanol amount （mg/L） to acetate amount （mg/L） was increased to 1.3 and polysaccharide was decreased to 2.5 mg/L. Moreover, the magnesium solution addition to the medium at different fermentation times affected hydrogen-producing ability. However, the later the addition time was postponed, the less the effect was on hydrogen evolution. Further experiments confirmed the enhancement was dependent on magnesium ions and not on the other inorganic ions such as SO42- or Cl-, which constituted the magnesium salts.展开更多
Environmental pollution with petroleum and petrochemical products such as diesel and used oils has been recognized as one of the most serious current problem in the world, especially in developing countries. These pet...Environmental pollution with petroleum and petrochemical products such as diesel and used oils has been recognized as one of the most serious current problem in the world, especially in developing countries. These petrochemical products devastate the soil, surface and underground waters and alter the microbial population at the polluted sites. Thus, the present work aims to optimize the biodegradation of diesel and two used oils (SAE 40 and SAE 50) by bacterial strains namely Acinetobacter S2 and Pseudomonas S7 using either nutrient factors (yeast extract, peptone or trace elements) or surfactants (tween 80 or Sodium Dodecyl Sulfate: SDS). The strains are incubated alone or together with the used oils or diesel supplemented or not with nutrient factors or surfactants for 14, 28, 42 and 56 days, respectively. For all the incubation period, the hydrocarbons degradation rates are determined by gravimetric assay. The results obtained show that nutrient factors increase significantly SAE 50 used oil biodegradation (p = 0.009). Similarly, tween 80 increases SAE 50 and SAE 40 used oils biodegradation but not diesel one. The results also show a significant difference between biodegradation rates at 14, 28, 42 and 56 days for all the hydro-carbons tested (p Acinetobacter S2 and Pseudomonas S7 increases the degradation over the one of the strains alone.展开更多
Cellulases are a group of enzymes that are used in many biotechnological processes. Since most of the enzymes synthesised by mesophilic microorganisms are unstable in industrial environments, it is necessary to direct...Cellulases are a group of enzymes that are used in many biotechnological processes. Since most of the enzymes synthesised by mesophilic microorganisms are unstable in industrial environments, it is necessary to direct research towards extremophile cellulolytic microorganisms because the enzymes synthesised by them are stable and active even in harsh physicochemical conditions. In the present investigation, our aim was to isolate and identify some microbial cellulolytic strains from a hypersaline lake located in Romania and to determine their optimal growth conditions. Of a total of 25 microbial strains isolated, only one extreme halotolerant bacterial strain was able to produce an endoglucanase. Based on molecular identification, we identified this cellulolytic strain as a species of Bacillus genus, most closely related to Bacillus zhangzhouensis. Optimal growth conditions were found to be at 15°C, pH 7.5 and 2 M NaCl. Endoglucanase activity of this bacterial strain is influenced by both salinity and temperature. The most significant endoglucanase activity was detected in the presence of 3 M NaCl, after 72 h of incubation at 15°C. In this situation, the amount of glucose released from a volume of 0.5 mL of 2% (w/v) carboxymethyl cellulose substrate is equivalent to 2.05 mg. In conclusion, this study represents the first preliminary characterization of a B. zhangzhouensis strain that has the ability to degrade cellulose and that demonstrates tolerance to high salt concentrations.展开更多
A set of near-isogenic rice lines withmonogenic resistance to bacterial blight weredeveloped by IRRI.The Cultivar IR24 wasused as the recurred parent.They wereevaluated with 6 races of Xanthomonascampestris pv.oryzae(...A set of near-isogenic rice lines withmonogenic resistance to bacterial blight weredeveloped by IRRI.The Cultivar IR24 wasused as the recurred parent.They wereevaluated with 6 races of Xanthomonascampestris pv.oryzae(Xco)in the Philip-pines at the maximum tillering and the bootingstages by ZHANG and MEW at IRRI in 1989.展开更多
Novel hierarchical flower-and nanorod-shaped ZnO nanoparticles with uniform morphological features were successfully synthesized through controlled precipitation method in aqueous media without using any surfactant or...Novel hierarchical flower-and nanorod-shaped ZnO nanoparticles with uniform morphological features were successfully synthesized through controlled precipitation method in aqueous media without using any surfactant or template.To elucidate the growth mechanism of the synthesized nanoparticles,the effects of pH,reaction time and temperature were studied systematically.Selected ZnO samples were then subjected to SEM,FT-IR and XRD analysis.XRD patterns confirmed well crystalline nature of the as-synthesized powders.Furthermore,synthesized nanoparticles(hierarchical flowers as ZnO-1 and nanorods as ZnO-2),as well as commercial ZnO(ZnO-Com),were then investigated for in-vitro evaluation of antibacterial activity against various bacterial strains of clinical importance.Results showed that ZnO-2 exhibited higher antibacterial activity to all tested strains than ZnO-1,while ZnO-Com showed no antibacterial response in the applied experimental conditions.In addition,ZnO concentration-dependent antibacterial study unfolded that size of inhibition zones increased significantly from^30 to 33 mm against Streptococcus mutans and from^28 to 30 mm against Escherichia coli with increasing ZnO-2 concentration from 0.25 to 0.75μg/μL.The present study,therefore,suggests that the application of synthesized ZnO nanoparticles as the antibacterial agent may be effective for inhibiting certain pathogenic bacteria in biomedical sides.展开更多
Astaxanthin is a value-added ketocarotenoid with great potential in nutraceutical and pharmaceutical industries.Genetic engineering of heterologous hosts for astaxanthin production has attracted great attention.In thi...Astaxanthin is a value-added ketocarotenoid with great potential in nutraceutical and pharmaceutical industries.Genetic engineering of heterologous hosts for astaxanthin production has attracted great attention.In this study,we assessed some key factors,including codon usage of the expressed genes,types of promoters,bacterial strains,and culture media,for engineered Escherichia coli to produce astaxanthin.The effect of codon usage was shown to be related to the types of promoters.E.coli DH5a was superior to other strains for astaxanthin production.Different culture media greatly affected the contents and yields of astaxanthin in engineered E.coli.When the expression cassette containing GadE promoter and its driving genes,HpCHY and CrBKT,was inserted into the plasmid pACCAR16DcrtX and expressed in E.coli DH5a,the engineered strain was able to produce 4.30±0.28 mg/g dry cell weight(DCW)or 24.16±2.03 mg/L of astaxanthin,which was a sevenfold or 40-fold increase over the initial production of 0.62±0.03 mg/g DCW or 0.61±0.05 mg/L.展开更多
Expanded granular sludge bed （EGSB） reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage （0 ...Expanded granular sludge bed （EGSB） reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage （0 - 24d） seeded with activated sludge, the butyric acid type-fermentation formed when the initial expanding rate, organic loading rate （OLR）, the initial redox potential （ORP） and hydraulic retention time （HRT） were 10%, 10.0 kg COD/（m^3·d）, -215 mV and 6.7 h, respectively. At the beginning of the second stage on day 25, the novel hydrogen-producing fermentative bacterial strain B49 （AF481148 in EMBL） were inoculated into the reactor under the condition of OLR 16. 0 kg COD/（m^3·d）, ORP and HRT about - 139 mV and 6.7 h, respectively, and then the reaction system transformed to ethanol-type fermentation gradually with the increase in OLR. When OLR, ORP and HRT were about 94.3 kg COD/（m^3·d）, -250 mV and 1.7 h, respectively, the system achieved the maximum hydrogen-producing rate of 282.6 mL H2/L reactor·h and hydrogen percentage of 51% -53% in the biogas.展开更多
A bacterial strain of the genus Pseudomonas aeruginosa was inoculated into a hydrocarbon culture medium and incubated for a definite period of time. The ability of the bacterial strain to biodegrade a hydrocarbon, viz...A bacterial strain of the genus Pseudomonas aeruginosa was inoculated into a hydrocarbon culture medium and incubated for a definite period of time. The ability of the bacterial strain to biodegrade a hydrocarbon, viz. n-hexadecane, was evaluated through determining the hexadecane concentration in the inoculated culture medium on a gas chromatograph (GC). The effect of pH value on the degrading ability of the bacterial isolate and the impact of temperature on microbial growth were also explored. Test results showed that Pseudomonas aeruginosa was markedly effective in biodegrading n-hexadecane. Furthermore, the ability of Pseudomonas aeruginosa to biodegrade n-hexadecane was different at various pH values. Pseudomonas aeruginosa provided excellent degrading ability at a pH value of 7.0. The microbial cells of Pseudomonas aeruginosa increased with an increasing incubation duration at temperatures ranging from 28 ℃ to 35 ℃, and an exponential phase of microbial growth was observed.展开更多
The internal mechanism of organizational learning and knowledge increase is very similar to the mechanism of biotic ferment, so we creatively use Knowledge Convening ＆ Fermenting Model （KCFM） to explain the origina...The internal mechanism of organizational learning and knowledge increase is very similar to the mechanism of biotic ferment, so we creatively use Knowledge Convening ＆ Fermenting Model （KCFM） to explain the origination and mechanism of knowledge increase, espec）ally clarifying that the original substance is the key factor to cause organizational learning and knowledge innovation, We also thoroughly analyze the helix process for knowledge bacterial strain to impel knowledge increase.展开更多
Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)are the most typical pathogenic bacteria with a significantly high risk of bio-contamination,widely existing in hospital and public places.Recent studies on a...Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)are the most typical pathogenic bacteria with a significantly high risk of bio-contamination,widely existing in hospital and public places.Recent studies on antibacterial materials and the related mechanisms have attracted more interests of researchers.However,the antibacterial behavior of materials is usually evaluated separately on the single bacterial strain,which is far from the practical condition.Actually,the interaction between the polymicrobial communities can promote the growing profile of bacteria,which may weaken the antibacterial effect of materials.In this work,a 420 copper-bearing martensitic stainless steel(420 CuSS)was studied with respect to its antibacterial activity and the underlying mechanism in a co-culturing infection model using both E.coli and S.au reus.Observed via plating and counting colony forming units(CFU),Cu releasing,and material characterization,420 CuSS was proved to present excellent antibacterial performance against the mixed bacteria with an approximately 99.4%of antibacterial rate.In addition,420 CuSS could effectively inhibit the biofilm formation on its surfaces,resulting from a synergistic antibacterial effect of Cu ions,Fe ions,reactive oxygen species(ROS),and proton consumption of bacteria.展开更多
Objective:To study the antibacterial activities of diethyl ether,toluene,ethanol and methanol extracts of red seaweeds such as Gracilaria crassa(G.crassa),Gracilaria folifera(G.folifera),Gracilaria debilis(G.debilis)a...Objective:To study the antibacterial activities of diethyl ether,toluene,ethanol and methanol extracts of red seaweeds such as Gracilaria crassa(G.crassa),Gracilaria folifera(G.folifera),Gracilaria debilis(G.debilis)and Gracilaria corticata.Methods:The crude extracts were tested against different types of Gram-positive and-negative bacterial strains and all the seaweed extracts were tested a broad spectrum of antibacterial activity.Antibacterial activity was made using paper disc diffusion method.Four organic solvents(diethyl ether,toluene,methanol and ethanol)were used separately in a Soxhlet apparatus for seven bacterial strains.Antibacterial activity of the known antibiotics such as chloramphenicol,streptomycin,kanamycin and ampicillin was determined by testing them against different test organisms.Results:The high antibacterial activity was noted in the extracts of G.crassa,G.folifera and G.debilis.However,G.crassa and G.debilis have good antibacterial activity.Pathogens like Bacillus subtilis and Escherichia coli were less susceptible to the methanol and diethyl ether extracts of G.folifera.The comparative study on the antibacterial activity was also made by using 200μg concentration of solvent extracts(diethyl ether,ethanol,toluene and methanol)and different five antibiotics such as chloramphenicol,streptomycin,kanamycin,amoxicillin and ampicillin.The bacterial strains tested were more sensitive to chloramphenicol,streptomycin,kanamycin,and ampicillin when compared to algal extracts.Conclusions:The present study proved that the extracts of G.crassa,G.folifera and G.debilis have high antibacterial activity.Although G.crassa and G.debilis showed good antibacterial activity,many known antibiotics are active against a few organisms individually.Hence,the extracts of seaweeds were active against all test organisms used and the activities were comparable to that of antibiotics and the seaweeds offer a feasible alternative for the development of new antibiotics.The results also suggest the need for a more dynamic search for pharmaceutically interesting substances from Indian seaweeds.展开更多
Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon （AOC） is an important parameter which determi...Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon （AOC） is an important parameter which determines the heterotrophic bacterial growth potential of water. Pseudomonas fluorescens P17 and Spirillum sp. NOX are widely used to measure AOC in drinking water. The AOC values of various reclaimed water samples determined by P 17 and NOX were compared with those determined by the new strains isolated from reclaimed water in this study. It showed that the conventional test strains were not suitable for AOC measurement of reclaimed water in certain cases. In addition to P17 and NOX, Stenotrophomonas sp. Z J2, Pseudomonas saponi- phila G3 and Enterobacter sp. G6, were selected as test strains for AOC measurement of reclaimed water. Key aspects of the bioassay including inoculum cell density, incubation temperature, incubation time and the pH of samples were evaluated for the newly selected test strains. Higher inoculum density （104 CFU.mL-1） and higher incubation temperature （25℃） could reduce the time required for the tests. The AOC results of various collected samples showed the advantages of the method proposed based on those five strains in evaluating the biologic stability of reclaimed water.展开更多
A bacterial strain, pcnb-21, capable of degrading pentaehloronitrobenzene （PCNB） under aerobic and anoxic conditions, was isolated from a long-term PCNB-polluted soil by an enrichment culture technique and identifie...A bacterial strain, pcnb-21, capable of degrading pentaehloronitrobenzene （PCNB） under aerobic and anoxic conditions, was isolated from a long-term PCNB-polluted soil by an enrichment culture technique and identified as Labrys portucalensis based upon its morphological, physiological and biochemical properties, as well as 16S rRNA gene sequence analysis. Effects of different factors, such as temperature and pH, on PCNB biodegradation were studied. Strain pcnb-21 efficiently degraded PCNB at temperatures from 20 to 30 ℃ and initial pH values from 4 to 7, which might be the first time that a Labrys strain was found capable of eflClciently degrading PC1NB. The degradation of PCNB was affected by oxygen, and the degradation decreased with increasing aeration. Exogenous electron donors such as glucose, lactic acid and succinic acid promoted the biodegradation of PCNB, while electron acceptors such as sodium nitrite, sodium sulfate, sodium nitrate and sodium sulfate inhibited PCNB biodegradation. The degradation of PCNB in sterile and non-sterile soils by a green fluorescent protein （GFP）-labeled strain, pcnb-21-gfp, was also studied. Cells of pcnb-21-gfp efficiently degraded 100 mg kg-1 PCNB in sterile and non-sterile soils and could not be detected after 42 days. Strain pcnb-21 might be useful in bioremediating PCNB-polluted soils and environment.展开更多
Glyphosate is an important organophosphonate herbicide used to eliminate grasses and herbaceous plants in many vegetation management situations.Its extensive use is causing environmental pollution,and consequently,the...Glyphosate is an important organophosphonate herbicide used to eliminate grasses and herbaceous plants in many vegetation management situations.Its extensive use is causing environmental pollution,and consequently,there is a need to remove it from the environment using an eco-friendly and cost-effective method.As a step to address this problem,a novel bacterial strain Comamonas odontotermitis F2,capable to utilize glyphosate as a carbon(C)and/or phosphorus(P)source,was isolated from a glyphostate-contaminated field soil in Australia and characterized.Response surface methodology(RSM)employing a 2^3 full factorial central composite design was used to optimize glyphosate degradation by C.odontotermitis P2 under various culture conditions.The strain C.odontotermitis P2 was proficient in degrading 1.5 g L^-1 glyphosate completely within 104 h.The optimal conditions for the degradation of glyphosate were found to be pH 7.4,29.9℃,and an inoculum density of 0.54 g L^-1,resulting in a maximum degradation of 90%.Sequencing of glyphosate oxidoreductase(GOX)and C-P lyase(phnJ)genes from C.odontotermitis P2 revealed 999c and 93%identities to already reported bacterial GOX and phnJ genes,respectively.The presence of these two genes in C.odontotermitis indicates its potential to degrade glyphosate through GOX and C-P lyase metabolic pathways.This study demonstrates the potential of C.odontotermitis P2 for efficient degradation of glyphosate,which can be exploited for remediation of glyphosate.展开更多
Six lactic acid bacterial （LAB） strains were isolated from traditionally fermented Xinjiang cheese and evaluated for functional and probiotic properties and potentials as starter cultures. The isolated six LAB strai...Six lactic acid bacterial （LAB） strains were isolated from traditionally fermented Xinjiang cheese and evaluated for functional and probiotic properties and potentials as starter cultures. The isolated six LAB strains com- prised Lactobacillus rhamnosus （one strain）, Lactobacillus helveticus （one strain）, and Enterococcus hirae （four strains）. All of the six strains were tolerant to acidic and bile salt conditions. Among which, the L. rhamnosus R4 strain showed more desirable antimicrobial, auto-aggregation, and hydrophobic activity. In addition, the strain L. rhamnosus R4 exhibited the highest level of free radical scavenging activity （53.78% of 1,1-dipheny1-2-picrylhydrazyl （DPPH） free radicals and 45.79% of hydroxyl radicals）. L. rhamnosus R4 also demonstrated cholesterol and triglyceride degrada- tion by 50.97% and 28.92%, respectively. To further examine the health-promoting effects of these LAB strains on host lifespan, Caenorhabditis elegans was used as an in vivo model. Worms fed LAB as a food source had significant differences in lifespan compared to those fed Escherichia coil OP50 （as a negative control）. Feeding of L. rhamnosus R4 extended the mean lifespan of C. elegans by up to 36.1% compared to that of the control. The results suggest that the strains isolated from Xinjiang fermented dairy products have high potential as starter cultures in the cheese industry.展开更多
基金Supported by Key R&D Project of Science&Technology Department of Ningxia Hui Autonomous Region(2021BBF02013)Post-doctoral Program of Hebei Province(2019003011)Hebei Province Innovation Ability Enhancement Plan Project(225676109H).
文摘[Objectives]The paper was to screen effective biocontrol strains against Meloidogyne incognita.[Methods]The effect of six bacterial strains sourced from the research group s strain library on the activity of second instar larvae of M.incognita,as well as on egg hatching,was evaluated.[Results]The treatment of fermentation supernatant derived from the X-2 strain exhibited a pronounced lethal effect on M.incognita,with a corrected mortality rate reaching 97%within 72 h.Additionally,this treatment significantly inhibited egg hatching,achieving an inhibition rate of 94.69%at a 20-fold dilution.The strain was identified as Bacillus velezensis,belonging to the genus Bacillus,and was designated as RKN1111.[Conclusions]This study presents alternative strains and a theoretical framework for the biological control of M.incognita.
文摘To investigate the characteristics of hydrogen production by a novel fermentative hydrogen-producing bacterial strain B49 (AF481148 in EMBL), batch experiments are conducted under different conditions. Hydrogen production has a correlation with cell growth and the consumption of glucose and soluble protein. The optimum pH for cell growth is 4.5±0.15. At acidic pH 4.0±0.15, the bacteria has the maximum accumulated hydrogen volume of 2382 ml/L culture and the maximum hydrogen evolution rate of 339.9 ml/L culture·h with 1% glucose. The optimum temperature for cell growth and hydrogen production is 35℃. In addition, fermentative hydrogen-producing bacterial strain B49 can generate hydrogen from the decomposition of other organic substrates such as wheat, soybean, corn, and potato. Moreover, it can also produce hydrogen from molasses wastewater and brewage wastewater, and hydrogen yields are 137.9 ml H 2/g COD and 49.9 ml H 2/g COD, respectively.
文摘Batch experiments were conducted to investigate the effects of magnesium on glucose metabolism, including growth and hydrogen-producing capacity of fermentative hydrogen-producing bacterial strain B49. These abilities were enhanced with an increase in magnesium concentration. At the end of fermentation from （10 g/L） glucose, for 10 mg/L MgCl2·6H2O the cell growth in terms of optical density （OD） at 600nm was 0.46, the ratio of ethanol amount （mg/L） to acetate amount （mg/L） was 1.1, and the accumulated hydrogen volume was 934.9 mL H2/L culture; for 200 mg/L of MgCl2·6H2O OD600 nm was increased to 1.34. The accumulated hydrogen volume was increased to 2 360.5 mL H2/L culture, the ratio of ethanol amount （mg/L） to acetate amount （mg/L） was increased to 1.3 and polysaccharide was decreased to 2.5 mg/L. Moreover, the magnesium solution addition to the medium at different fermentation times affected hydrogen-producing ability. However, the later the addition time was postponed, the less the effect was on hydrogen evolution. Further experiments confirmed the enhancement was dependent on magnesium ions and not on the other inorganic ions such as SO42- or Cl-, which constituted the magnesium salts.
文摘Environmental pollution with petroleum and petrochemical products such as diesel and used oils has been recognized as one of the most serious current problem in the world, especially in developing countries. These petrochemical products devastate the soil, surface and underground waters and alter the microbial population at the polluted sites. Thus, the present work aims to optimize the biodegradation of diesel and two used oils (SAE 40 and SAE 50) by bacterial strains namely Acinetobacter S2 and Pseudomonas S7 using either nutrient factors (yeast extract, peptone or trace elements) or surfactants (tween 80 or Sodium Dodecyl Sulfate: SDS). The strains are incubated alone or together with the used oils or diesel supplemented or not with nutrient factors or surfactants for 14, 28, 42 and 56 days, respectively. For all the incubation period, the hydrocarbons degradation rates are determined by gravimetric assay. The results obtained show that nutrient factors increase significantly SAE 50 used oil biodegradation (p = 0.009). Similarly, tween 80 increases SAE 50 and SAE 40 used oils biodegradation but not diesel one. The results also show a significant difference between biodegradation rates at 14, 28, 42 and 56 days for all the hydro-carbons tested (p Acinetobacter S2 and Pseudomonas S7 increases the degradation over the one of the strains alone.
文摘Cellulases are a group of enzymes that are used in many biotechnological processes. Since most of the enzymes synthesised by mesophilic microorganisms are unstable in industrial environments, it is necessary to direct research towards extremophile cellulolytic microorganisms because the enzymes synthesised by them are stable and active even in harsh physicochemical conditions. In the present investigation, our aim was to isolate and identify some microbial cellulolytic strains from a hypersaline lake located in Romania and to determine their optimal growth conditions. Of a total of 25 microbial strains isolated, only one extreme halotolerant bacterial strain was able to produce an endoglucanase. Based on molecular identification, we identified this cellulolytic strain as a species of Bacillus genus, most closely related to Bacillus zhangzhouensis. Optimal growth conditions were found to be at 15°C, pH 7.5 and 2 M NaCl. Endoglucanase activity of this bacterial strain is influenced by both salinity and temperature. The most significant endoglucanase activity was detected in the presence of 3 M NaCl, after 72 h of incubation at 15°C. In this situation, the amount of glucose released from a volume of 0.5 mL of 2% (w/v) carboxymethyl cellulose substrate is equivalent to 2.05 mg. In conclusion, this study represents the first preliminary characterization of a B. zhangzhouensis strain that has the ability to degrade cellulose and that demonstrates tolerance to high salt concentrations.
文摘A set of near-isogenic rice lines withmonogenic resistance to bacterial blight weredeveloped by IRRI.The Cultivar IR24 wasused as the recurred parent.They wereevaluated with 6 races of Xanthomonascampestris pv.oryzae(Xco)in the Philip-pines at the maximum tillering and the bootingstages by ZHANG and MEW at IRRI in 1989.
文摘Novel hierarchical flower-and nanorod-shaped ZnO nanoparticles with uniform morphological features were successfully synthesized through controlled precipitation method in aqueous media without using any surfactant or template.To elucidate the growth mechanism of the synthesized nanoparticles,the effects of pH,reaction time and temperature were studied systematically.Selected ZnO samples were then subjected to SEM,FT-IR and XRD analysis.XRD patterns confirmed well crystalline nature of the as-synthesized powders.Furthermore,synthesized nanoparticles(hierarchical flowers as ZnO-1 and nanorods as ZnO-2),as well as commercial ZnO(ZnO-Com),were then investigated for in-vitro evaluation of antibacterial activity against various bacterial strains of clinical importance.Results showed that ZnO-2 exhibited higher antibacterial activity to all tested strains than ZnO-1,while ZnO-Com showed no antibacterial response in the applied experimental conditions.In addition,ZnO concentration-dependent antibacterial study unfolded that size of inhibition zones increased significantly from^30 to 33 mm against Streptococcus mutans and from^28 to 30 mm against Escherichia coli with increasing ZnO-2 concentration from 0.25 to 0.75μg/μL.The present study,therefore,suggests that the application of synthesized ZnO nanoparticles as the antibacterial agent may be effective for inhibiting certain pathogenic bacteria in biomedical sides.
基金This study was supported by a research grant from Department of Economic Plants and Biotechnology,Yunnan Key Laboratory for Wild Plant Resources,Kunming Institute of Botany,Chinese Academy of Sciences.
文摘Astaxanthin is a value-added ketocarotenoid with great potential in nutraceutical and pharmaceutical industries.Genetic engineering of heterologous hosts for astaxanthin production has attracted great attention.In this study,we assessed some key factors,including codon usage of the expressed genes,types of promoters,bacterial strains,and culture media,for engineered Escherichia coli to produce astaxanthin.The effect of codon usage was shown to be related to the types of promoters.E.coli DH5a was superior to other strains for astaxanthin production.Different culture media greatly affected the contents and yields of astaxanthin in engineered E.coli.When the expression cassette containing GadE promoter and its driving genes,HpCHY and CrBKT,was inserted into the plasmid pACCAR16DcrtX and expressed in E.coli DH5a,the engineered strain was able to produce 4.30±0.28 mg/g dry cell weight(DCW)or 24.16±2.03 mg/L of astaxanthin,which was a sevenfold or 40-fold increase over the initial production of 0.62±0.03 mg/g DCW or 0.61±0.05 mg/L.
文摘Expanded granular sludge bed （EGSB） reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage （0 - 24d） seeded with activated sludge, the butyric acid type-fermentation formed when the initial expanding rate, organic loading rate （OLR）, the initial redox potential （ORP） and hydraulic retention time （HRT） were 10%, 10.0 kg COD/（m^3·d）, -215 mV and 6.7 h, respectively. At the beginning of the second stage on day 25, the novel hydrogen-producing fermentative bacterial strain B49 （AF481148 in EMBL） were inoculated into the reactor under the condition of OLR 16. 0 kg COD/（m^3·d）, ORP and HRT about - 139 mV and 6.7 h, respectively, and then the reaction system transformed to ethanol-type fermentation gradually with the increase in OLR. When OLR, ORP and HRT were about 94.3 kg COD/（m^3·d）, -250 mV and 1.7 h, respectively, the system achieved the maximum hydrogen-producing rate of 282.6 mL H2/L reactor·h and hydrogen percentage of 51% -53% in the biogas.
基金support provided by the National Natural Science Foundation of China (project No. 50975282)the Natural Science Foundation for Outstanding Youths, Chongqing, China (project No. CSTC,2008BA4037)
文摘A bacterial strain of the genus Pseudomonas aeruginosa was inoculated into a hydrocarbon culture medium and incubated for a definite period of time. The ability of the bacterial strain to biodegrade a hydrocarbon, viz. n-hexadecane, was evaluated through determining the hexadecane concentration in the inoculated culture medium on a gas chromatograph (GC). The effect of pH value on the degrading ability of the bacterial isolate and the impact of temperature on microbial growth were also explored. Test results showed that Pseudomonas aeruginosa was markedly effective in biodegrading n-hexadecane. Furthermore, the ability of Pseudomonas aeruginosa to biodegrade n-hexadecane was different at various pH values. Pseudomonas aeruginosa provided excellent degrading ability at a pH value of 7.0. The microbial cells of Pseudomonas aeruginosa increased with an increasing incubation duration at temperatures ranging from 28 ℃ to 35 ℃, and an exponential phase of microbial growth was observed.
基金This paper is supported by National Nature Science Foundation of China （NSFC） and Ph.D. research fund.
文摘The internal mechanism of organizational learning and knowledge increase is very similar to the mechanism of biotic ferment, so we creatively use Knowledge Convening ＆ Fermenting Model （KCFM） to explain the origination and mechanism of knowledge increase, espec）ally clarifying that the original substance is the key factor to cause organizational learning and knowledge innovation, We also thoroughly analyze the helix process for knowledge bacterial strain to impel knowledge increase.
基金financially supported by the National Natural Science Foundation of China(Nos.51101154,51631009,51672184,and 51371168)the National Basic Research Program of China(No.2012CB619101)National Key R&D Program of China(No.2020YFC1107400)。
文摘Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)are the most typical pathogenic bacteria with a significantly high risk of bio-contamination,widely existing in hospital and public places.Recent studies on antibacterial materials and the related mechanisms have attracted more interests of researchers.However,the antibacterial behavior of materials is usually evaluated separately on the single bacterial strain,which is far from the practical condition.Actually,the interaction between the polymicrobial communities can promote the growing profile of bacteria,which may weaken the antibacterial effect of materials.In this work,a 420 copper-bearing martensitic stainless steel(420 CuSS)was studied with respect to its antibacterial activity and the underlying mechanism in a co-culturing infection model using both E.coli and S.au reus.Observed via plating and counting colony forming units(CFU),Cu releasing,and material characterization,420 CuSS was proved to present excellent antibacterial performance against the mixed bacteria with an approximately 99.4%of antibacterial rate.In addition,420 CuSS could effectively inhibit the biofilm formation on its surfaces,resulting from a synergistic antibacterial effect of Cu ions,Fe ions,reactive oxygen species(ROS),and proton consumption of bacteria.
文摘Objective:To study the antibacterial activities of diethyl ether,toluene,ethanol and methanol extracts of red seaweeds such as Gracilaria crassa(G.crassa),Gracilaria folifera(G.folifera),Gracilaria debilis(G.debilis)and Gracilaria corticata.Methods:The crude extracts were tested against different types of Gram-positive and-negative bacterial strains and all the seaweed extracts were tested a broad spectrum of antibacterial activity.Antibacterial activity was made using paper disc diffusion method.Four organic solvents(diethyl ether,toluene,methanol and ethanol)were used separately in a Soxhlet apparatus for seven bacterial strains.Antibacterial activity of the known antibiotics such as chloramphenicol,streptomycin,kanamycin and ampicillin was determined by testing them against different test organisms.Results:The high antibacterial activity was noted in the extracts of G.crassa,G.folifera and G.debilis.However,G.crassa and G.debilis have good antibacterial activity.Pathogens like Bacillus subtilis and Escherichia coli were less susceptible to the methanol and diethyl ether extracts of G.folifera.The comparative study on the antibacterial activity was also made by using 200μg concentration of solvent extracts(diethyl ether,ethanol,toluene and methanol)and different five antibiotics such as chloramphenicol,streptomycin,kanamycin,amoxicillin and ampicillin.The bacterial strains tested were more sensitive to chloramphenicol,streptomycin,kanamycin,and ampicillin when compared to algal extracts.Conclusions:The present study proved that the extracts of G.crassa,G.folifera and G.debilis have high antibacterial activity.Although G.crassa and G.debilis showed good antibacterial activity,many known antibiotics are active against a few organisms individually.Hence,the extracts of seaweeds were active against all test organisms used and the activities were comparable to that of antibiotics and the seaweeds offer a feasible alternative for the development of new antibiotics.The results also suggest the need for a more dynamic search for pharmaceutically interesting substances from Indian seaweeds.
文摘Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon （AOC） is an important parameter which determines the heterotrophic bacterial growth potential of water. Pseudomonas fluorescens P17 and Spirillum sp. NOX are widely used to measure AOC in drinking water. The AOC values of various reclaimed water samples determined by P 17 and NOX were compared with those determined by the new strains isolated from reclaimed water in this study. It showed that the conventional test strains were not suitable for AOC measurement of reclaimed water in certain cases. In addition to P17 and NOX, Stenotrophomonas sp. Z J2, Pseudomonas saponi- phila G3 and Enterobacter sp. G6, were selected as test strains for AOC measurement of reclaimed water. Key aspects of the bioassay including inoculum cell density, incubation temperature, incubation time and the pH of samples were evaluated for the newly selected test strains. Higher inoculum density （104 CFU.mL-1） and higher incubation temperature （25℃） could reduce the time required for the tests. The AOC results of various collected samples showed the advantages of the method proposed based on those five strains in evaluating the biologic stability of reclaimed water.
基金Supported by the National High Technology Research and Development Program of China (No. 2007AA10Z405)the National Natu-ral Science Foundation of China (No. 31070100)the Key Technology R&D Program of Jiangsu Province,China (No. BE2008669)
文摘A bacterial strain, pcnb-21, capable of degrading pentaehloronitrobenzene （PCNB） under aerobic and anoxic conditions, was isolated from a long-term PCNB-polluted soil by an enrichment culture technique and identified as Labrys portucalensis based upon its morphological, physiological and biochemical properties, as well as 16S rRNA gene sequence analysis. Effects of different factors, such as temperature and pH, on PCNB biodegradation were studied. Strain pcnb-21 efficiently degraded PCNB at temperatures from 20 to 30 ℃ and initial pH values from 4 to 7, which might be the first time that a Labrys strain was found capable of eflClciently degrading PC1NB. The degradation of PCNB was affected by oxygen, and the degradation decreased with increasing aeration. Exogenous electron donors such as glucose, lactic acid and succinic acid promoted the biodegradation of PCNB, while electron acceptors such as sodium nitrite, sodium sulfate, sodium nitrate and sodium sulfate inhibited PCNB biodegradation. The degradation of PCNB in sterile and non-sterile soils by a green fluorescent protein （GFP）-labeled strain, pcnb-21-gfp, was also studied. Cells of pcnb-21-gfp efficiently degraded 100 mg kg-1 PCNB in sterile and non-sterile soils and could not be detected after 42 days. Strain pcnb-21 might be useful in bioremediating PCNB-polluted soils and environment.
基金We acknowledge Higher Education Commission (HEC), Islamabad, Pakistan, for providing financial support through International Research Support Initiative Program (IRSIP) to conduct this research at University of Sydney, Australia.
文摘Glyphosate is an important organophosphonate herbicide used to eliminate grasses and herbaceous plants in many vegetation management situations.Its extensive use is causing environmental pollution,and consequently,there is a need to remove it from the environment using an eco-friendly and cost-effective method.As a step to address this problem,a novel bacterial strain Comamonas odontotermitis F2,capable to utilize glyphosate as a carbon(C)and/or phosphorus(P)source,was isolated from a glyphostate-contaminated field soil in Australia and characterized.Response surface methodology(RSM)employing a 2^3 full factorial central composite design was used to optimize glyphosate degradation by C.odontotermitis P2 under various culture conditions.The strain C.odontotermitis P2 was proficient in degrading 1.5 g L^-1 glyphosate completely within 104 h.The optimal conditions for the degradation of glyphosate were found to be pH 7.4,29.9℃,and an inoculum density of 0.54 g L^-1,resulting in a maximum degradation of 90%.Sequencing of glyphosate oxidoreductase(GOX)and C-P lyase(phnJ)genes from C.odontotermitis P2 revealed 999c and 93%identities to already reported bacterial GOX and phnJ genes,respectively.The presence of these two genes in C.odontotermitis indicates its potential to degrade glyphosate through GOX and C-P lyase metabolic pathways.This study demonstrates the potential of C.odontotermitis P2 for efficient degradation of glyphosate,which can be exploited for remediation of glyphosate.
基金supported by the National Key Technology R&D Program of China(No.2012BAD33B08)the Zhejiang Provincial Natural Science Foundation of China(No.LY12B06006)+1 种基金the Research Program of Education Department of Zhejiang Province(No.Y201122061)the National Natural Science Foundation of China(No.20906060)
文摘Six lactic acid bacterial （LAB） strains were isolated from traditionally fermented Xinjiang cheese and evaluated for functional and probiotic properties and potentials as starter cultures. The isolated six LAB strains com- prised Lactobacillus rhamnosus （one strain）, Lactobacillus helveticus （one strain）, and Enterococcus hirae （four strains）. All of the six strains were tolerant to acidic and bile salt conditions. Among which, the L. rhamnosus R4 strain showed more desirable antimicrobial, auto-aggregation, and hydrophobic activity. In addition, the strain L. rhamnosus R4 exhibited the highest level of free radical scavenging activity （53.78% of 1,1-dipheny1-2-picrylhydrazyl （DPPH） free radicals and 45.79% of hydroxyl radicals）. L. rhamnosus R4 also demonstrated cholesterol and triglyceride degrada- tion by 50.97% and 28.92%, respectively. To further examine the health-promoting effects of these LAB strains on host lifespan, Caenorhabditis elegans was used as an in vivo model. Worms fed LAB as a food source had significant differences in lifespan compared to those fed Escherichia coil OP50 （as a negative control）. Feeding of L. rhamnosus R4 extended the mean lifespan of C. elegans by up to 36.1% compared to that of the control. The results suggest that the strains isolated from Xinjiang fermented dairy products have high potential as starter cultures in the cheese industry.
