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1.
The toxicity of organic plant extracts to Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) was assessed for three tropical plant species: branches, leaves, and seeds of Annona montana (Annonaceae), branches of Aristolochia paulistana (Aristolochiaceae), and leaves and branches of Casearia sylvestris (Salicaceae). The screening assay resulted that the extracts of A. montana seeds obtained with hexane (LC50?=?534.75 mg kg?1 and LT50?=?6.10 days) and with dichloromethane (LC50?=?424.67 mg kg?1 and LT50?=?5.03 days) were the most promising treatments, followed by the extract prepared from A. montana leaves with hexane (LC50?=?837.70 mg kg?1 and LT50?=?4.90 days). Moreover, extracts (at 1,500 mg kg?1) prepared from C. sylvestris branches with dichloromethane and A. paulistana with hexane caused significant mortality (37% and 41.5%, respectively) beyond sublethal effects on S. zeamais. Therefore, based on the biological assays, extraction yield, and evaluation of the chromatographic profile of the crude extracts by TLC, the hexane extract of A. montana seeds was selected and fractioned using liquid-liquid partitioning. The hydroalcoholic fraction caused mortality of 55.5%, significantly superior to dichloromethane fraction, which caused 35.5% of mortality. Chemical analyses (1H NMR, HPLC, and TLC) were performed, and the results showed the presence of alkaloids and acetogenins in both active fractions, which have been associated with bioactivity. Therefore, extracts prepared from A. montana seeds (especially) is an interesting source of new compounds with promising grain-protectant properties.  相似文献   

2.
The hydrolytic activity of a recombinant β-glycosidase from Dictyoglomus turgidum that specifically hydrolyzed the xylose at the C-6 position and the glucose in protopanaxatriol (PPT)-type ginsenosides followed the order Rf > Rg1 > Re > R1 > Rh1 > R2. The production of aglycone protopanaxatriol (APPT) from ginsenoside Rf was optimal at pH 6.0, 80 °C, 1 mg ml?1 Rf, and 10.6 U ml?1 enzyme. Under these conditions, D. turgidum β-glycosidase converted ginsenoside R1 to APPT with a molar conversion yield of 75.6 % and a productivity of 15 mg l?1 h?1 after 24 h by the transformation pathway of R1 → R2 → Rh1 → APPT, whereas the complete conversion of ginsenosides Rf and Rg1 to APPT was achieved with a productivity of 1,515 mg l?1 h?1 after 6.6 h by the pathways of Rf → Rh1 → APPT and Rg1 → Rh1 → APPT, respectively. In addition, D. turgidum β-glycosidase produced 0.54 mg ml?1 APPT from 2.29 mg ml?1 PPT-type ginsenosides of Panax ginseng root extract after 24 h, with a molar conversion yield of 43.2 % and a productivity of 23 mg l?1 h?1, and 0.62 mg ml?1 APPT from 1.35 mg ml?1 PPT-type ginsenosides of Panax notoginseng root extract after 20 h, with a molar conversion yield of 81.2 % and a productivity of 31 mg l?1 h?1. This is the first report on the APPT production from ginseng root extract. Moreover, the concentrations, yields, and productivities of APPT achieved in the present study are the highest reported to date.  相似文献   

3.
The effects of a bioinsecticide formulation based on extract of Annona squamosa L. (Annonaceae) containing 10,000 mg L?1 of acetogenin annonin as the main active ingredient were investigated against three primary pest species of stored grains in Brazil [maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), Mexican bean weevil Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae: Bruchinae), and cowpea weevil Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae: Bruchinae)] by means of residual contact bioassays. In a concentration-dependent manner, the annonin-based commercial bioinsecticide caused significant adult mortality of C. maculatus (LC50 = 6890 μL kg?1), S. zeamais (LC50 = 2781 μL kg?1), and Z. subfasciatus (LC50 = 2120 μL kg?1) after 120 h of residual contact exposure. In addition to acute toxicity, the tested bioinsecticide also promoted a significant reduction of the number of eggs laid by females of C. maculatus (EC50 = 5949.7 μL kg?1) and Z. subfasciatus (EC50 = 552.7 μL kg?1). Moreover, the bioinsecticide significantly reduced the number of emerged insects (F1 generation) of C. maculatus (EC50 = 2763.0 μL kg?1), S. zeamais (EC50 = 1380.8 μL kg?1), and Z. subfasciatus (EC50 = 561.5 μL kg?1). The bioinsecticide also reduced the percentage of damaged grains for the three pest species studied, and its grain-protectant properties are comparable to or superior in efficacy in relation to a diatomaceous earth-based insecticide (Insecto® at 1000 mg kg?1) used as a positive control. Thus, this standardized formulation has promising bioactivity against stored insect species and can be a useful component for IPM of stored grains in Brazil and elsewhere.  相似文献   

4.
Sublethal concentrations of chemical insecticides may cause changes in some behavioral characteristics of natural enemies such as functional responses. The residual effect of three synthetic insecticides including deltamethrin, fenvalerate and azadirachtin were studied on functional response of Habrobracon hebetor Say to Ephestia kuehniella Zeller larvae. Seven host densities (2, 4, 8, 16, 32, 64 and 96) were used during a 24 h period. The resulting data were appropriately fit to Type II functional response models in all treatments: (1) control (0.0916 h?1; and T h  = 0.2011 h); (2) deltamethrin (a = 0.0839 h?1; and T h  = 0.3560 h); (3) fenvalerate (a = 0.0808 h?1 and T h  = 0.3623 h); and (4) azadirachtin (a = 0.0900 h?1 and T h  = 0.2042 h). Maximum theoretical parasitism rate (T/T h ) was 119.34 estimated for control wasps. There was no significant difference between the values of attack rates (a and a + D a ) in all treatments while the handling time was statistically affected in female wasps treated with fenvalerate. Our findings will be useful in safe application of these insecticides in pest management programmes.  相似文献   

5.
The soybean looper Chrysodeixis includens (Lepidoptera: Noctuidae) is a pest of the soya bean, and increasing populations have been observed on several crops in Brazil. Control of this pest is accomplished using insecticides, particularly with new products recently launched in the market. The effectiveness of these insecticides against C. includens and their impact on natural enemies need further study. Therefore, this study aimed to determine the toxicity of nine insecticides for C. includens and their effects on the Blaptostethus pallescens. Toxicity was increased via the addition of an insecticide synergist, and behavioural changes in Blaptostethus pallescens, an anthocorid predator of C. includens, were assessed. Except for acephate, all other insecticides showed high toxicity to C. includens (mortality >80%). The estimated lethal time (LT50) for C. includens was shorter for methomyl, cartap and spinosad than others six insecticides tested in this work. Chlorantraniliprole, chlorfenapyr, deltamethrin, flubendiamide, indoxacarb and spinosad showed selectivity for the predator B. pallescens and exhibited a lower toxicity to the predator than to C. includens. The detoxifying enzymes monooxygenase and glutathione S‐transferase may be involved in the selectivity mechanisms of these insecticides for the predator based on the results obtained with the synergized insecticides. Only the insecticides cartap, indoxacarb and spinosad changed the behaviour of the predator B. pallescens. These three insecticides are repellent, and the predator avoids them. However, the predator tended to remain on the surface treated with flubendiamide longer. Our results suggest that the insecticides chlorfenapyr, chlorantraniliprole, flubendiamide, spinosad and indoxacarb are the most promising compounds for use against C. includens. These compounds also preserve populations of B. pallescens and allow more sustainable integrated pest management programmes.  相似文献   

6.
The organophosphate pesticide chlorpyrifos (CP) has been used extensively since the 1960s for insect control. However, its toxic effects on mammals and persistence in environment necessitate its removal from contaminated sites, biodegradation studies of CP-degrading microbes are therefore of immense importance. Samples from a Pakistani agricultural soil with an extensive history of CP application were used to prepare enrichment cultures using CP as sole carbon source for bacterial community analysis and isolation of CP metabolizing bacteria. Bacterial community analysis (denaturing gradient gel electrophoresis) revealed that the dominant genera enriched under these conditions were Pseudomonas, Acinetobacter and Stenotrophomonas, along with lower numbers of Sphingomonas, Agrobacterium and Burkholderia. Furthermore, it revealed that members of Bacteroidetes, Firmicutes, α- and γ-Proteobacteria and Actinobacteria were present at initial steps of enrichment whereas β-Proteobacteria appeared in later steps and only Proteobacteria were selected by enrichment culturing. However, when CP-degrading strains were isolated from this enrichment culture, the most active organisms were strains of Acinetobacter calcoaceticus, Pseudomonas mendocina and Pseudomonas aeruginosa. These strains degraded 6–7.4 mg L?1 day?1 of CP when cultivated in mineral medium, while the consortium of all four strains degraded 9.2 mg L?1 day?1 of CP (100 mg L?1). Addition of glucose as an additional C source increased the degradation capacity by 8–14 %. After inoculation of contaminated soil with CP (200 mg kg?1) disappearance rates were 3.83–4.30 mg kg?1 day?1 for individual strains and 4.76 mg kg?1 day?1 for the consortium. These results indicate that these organisms are involved in the degradation of CP in soil and represent valuable candidates for in situ bioremediation of contaminated soils and waters.  相似文献   

7.
8.
Glucosamine-6-phosphate (GlcN-6-P) synthase from Saccharomyces cerevisiae was expressed in Pichia pastoris SMD1168 GIVING maximum activity of 96 U ml?1 for the enzyme in the culture medium. By SDS-PAGE, the enzyme, a glycosylated protein, had an apparent molecular mass of 90 kDa. The enzyme was purified by gel exclusion chromatography to near homogeneity, with a 90 % yield and its properties were characterized. Optimal activities were at pH 5.5 and 55 °C, respectively, at which the highest specific activity was 6.8 U mg protein ?1. The enzyme was stable from pH 4.5 to 5.5 and from 45 to 60 °C. The Km and Vmax of the GlcN-6-P synthase towards d-fructose 6-phosphate were 2.8 mM and 6.9 μmol min?1 mg?1, respectively.  相似文献   

9.
Fusarium species isolated from Belgian maize were screened for their ability to produce fusarin C, fusaric acid, fumonisins B1 (FB1), FB2 and FB3 in maize grains. First, cultivation of Fusarium species in Myro liquid medium allowed overcoming the shortage of the standard of fusarin C on the market. All Fusarium verticillioides produced much higher contents of mycotoxins in Myro compared to Fusarium graminearum or Fusarium venenatum. The optimization of the LC-MS/MS method resulted in low limits of detection and quantification for fusarin C, fusaric acid, FB1, FB2 and FB3 determination in maize grains. Its application for screening the potential toxin production ability evidenced that the concentrations of the analytes were significantly increased at various levels when F. verticillioides strains were cultivated in maize grains and reached 441 mg kg?1 for fusaric acid, 74 mg kg?1 for fusarin C, 1,301 mg kg?1 for FB1, 367 mg kg?1 for FB2 and 753 mg kg?1 for FB3.  相似文献   

10.
Over-expression of the gene, mshA, coding for mycothiol glycosyl transferase improved the robustness of Corynebacterium glutamicum to various stresses. Intracellular mycothiol (MSH) content was increased by 114 % in WT(pXMJ19-mshA) compared to WT(pXMJ19). Survival rates increased by 44, 39, 90, 77, 131, 87, 52, 47, 57, 85 and 33 % as compared to WT(pXMJ19) under stress by H2O2 (40 mM), methylglyoxal (5.8 mM), erythromycin (0.08 mg ml?1), streptomycin (0.005 mg ml?1), Cd2+ (0.01 mM), Mn2+ (2 mM), formic acid (0.05 %), acetic acid (0.15 %), levulinic acid (0.25 %), furfural (7.2 mM), and ethanol (10 % v/v), respectively. Increased MSH content also decreased the concentration of reactive oxygen species in the presence of the above stresses. Our results may open a new avenue for enhancing robustness of industrial bacteria for production of commodity chemicals.  相似文献   

11.
Twenty local isolates of entomopathogenic fungi were determined for control of the larvae and adults of Culex quinquefasciatus. In a laboratory experiment, a Penicillium sp. CM-010 caused 100 % mortality of third-instar larvae within 2 h using a conidial suspension of 1 × 106 conidia ml?1. Its LC50 was 3 × 105 conidia ml?1, and the lethal time (LT50) was 1.06 h. Cloning and sequencing of its internal transcribed spacer region indicated that this Penicillium species is Penicillium citrinum (100 % identity in 434 bp). Mortality of the adult was highest with Aspergillus flavus CM-011 followed with Metarhizium anisopliae CKM-048 from 1 × 109 conidia ml?1. P. citrinum CM-010 at 1 × 106 conidia ml?1 killed 100 % larvae within 2 h while Bacillus thuringiensis var. israelensis at 5 ITU ml?1 required 24 h. This P. citrinum CM-010 also greatly reduced survival of C. quinquefasciatus larvae in an unreplicated field test. Light and transmission electron micrographs showed that the fungal conidia were ingested by the larvae and deposited in the gut. The metabolite patulin was produced by P. citrinum CM-010 instead of citrinin.  相似文献   

12.
Hypocryphalus mangiferae Stebbing is one of the most destructive insect pests of mango trees and is found to be associated with the transmission of causal organisms of mango sudden death disease. The present study was carried out to evaluate the toxicity of deltamethrin, bifenthrin, chlorpyrifos, emamectin benzoate, imidacloprid and spinosad in laboratory and field trials. Bioassay results showed that the toxicity of chlorpyrifos was significantly higher than deltamethrin but similar to bifenthrin. Deltamethrin and bifenthrin toxicity, however, increased significantly (P < 0.01) from day 1 to day 3. Spinosad was the least toxic compound while emamectin was the most toxic among new chemical insecticides tested, but its toxicity increased significantly from day 1 to day 5. Comparison of the efficacies of the insecticides using lethal times to produce 50% mortality (LT50) and 90% mortality (LT90) showed that the relative potencies of chlorpyrifos, emamectin, imidacloprid and spinosad were greater than bifenthrin and deltamethrin. The results of field trials showed the highest number of beetles emerged from the control twigs while significantly fewer beetles emerged from the twigs treated with bifenthrin (P < 0.05), which accounted for 12% for bifenthrin compared to that of the control. The present study demonstrated increased toxicities of systemic insecticides and chlorpyrifos compared to toxicities of deltamethrin and bifenthrin, suggesting these insecticides could be an alternative tool in a comprehensive H. mangiferae management program to eradicate the beetles from mango orchards.  相似文献   

13.
14.
Ginsenoside Rb2 was transformed by recombinant glycosidase (Bgp2) into ginsenosides Rd and 20(S)-Rg3. The bgp2 gene consists of 2,430 bp that encode 809 amino acids, and this gene has homology to the glycosyl hydrolase family 2 protein domain. SDS-PAGE was used to determine that the molecular mass of purified Bgp2 was 87 kDa. Using 0.1 mg ml?1 of enzyme in 20 mM sodium phosphate buffer at 40 °C and pH 7.0, 1.0 mg ml?1 ginsenoside Rb2 was transformed into 0.47 mg ml?1 ginsenoside 20(S)-Rg3 within 120 min, with a corresponding molar conversion yield of 65 %. Bgp2 hydrolyzed the ginsenoside Rb2 along the following pathway: Rb2 → Rd → 20(S)-Rg3. This is the first report of the biotransformation of ginsenoside Rb2 to ginsenoside 20(S)-Rg3 using the recombinant glycosidase.  相似文献   

15.
Callus cultures of the endemic South-African legume Cyclopia subternata were cultivated under varying light and temperature conditions to determine their influence on biomass growth and bioflavonoids accumulation. Experimental modifications of light included complete darkness, light of different spectral quality (white, red, blue and yellow) and ultraviolet C (UVC) irradiation. The calli were also subjected to elevated temperature or cold stress. Among the tested light regimes, cultivation under blue light resulted in the highest levels of hesperidin (H)—118.00 mg 100 g?1 dry weight (DW) on 28 days of experiment, as well as isoflavones: 7-O-β-glucosides of calycosin (CG), pseudobaptigenin (PG) and formononetin (FG)—28.74, 19.26 and 10.32 mg 100 g?1 DW, respectively, in 14-days old calli. UVC irradiation applied on 20 days stimulated the accumulation of H (204.14 mg 100 g?1 DW), CG (31.84 mg 100 g?1 DW) and PG (18.09 mg 100 g?1 DW) in 28 days culture by 140, 46 and 165 %, respectively, without negatively influencing callus growth. Low temperature (13 °C) increased CG content by over 1,500 % (235.29 mg 100 g?1 DW) when applied during the whole 28-days growth cycle, at the same time causing 95 % decrease in culture growth in comparison to reference calli maintained at 24 °C. On the contrary, elevated temperature (29 °C) applied during the second half of the culture period resulted in over 300 and 500 % increase in CG and PG content (61.76 and 58.89 mg 100 g?1, respectively) while maintaining relatively high biomass yield.  相似文献   

16.
A new serine protease with fibrinolytic activity from a marine invertebrate, Urechis unicinctus, was purified to electrophoretic homogeneity using column chromatography. SDS-PAGE of the purified enzyme showed a single polypeptide chain with MW ~20.8 kDa. Its N-terminal sequence was IIGGSQAAITSY. The purified enzyme, UFEIII, was stable at pH 6–10 below 60 °C with an optimum pH of 8.5 at approx. 55 °C. The enzyme activity was significantly inhibited by PMSF and SBTI suggesting that it was a serine protease. In fibrin plate assays, UFEIII was contained 1.46 × 10U (urokinase units) mg?1 total fibrinolytic activity, which consisted of 692 U mg?1 direct fibrinolytic activity and 769 U mg?1 plasminogen-activator activity. Km and Vmax values for azocasein were 1 mg ml?1 and 43 μg min?1 ml?1, respectively.  相似文献   

17.
A codon-optimized Escherichia coli appA phytase gene was synthesized and expressed in Pichia pastoris. Two residue substitutions (Q258N, Q349N) were sequentially introduced to enhance its glycosylation activity. Secretion of appA-Q258N/Q349N was approx. 0.3 mg ml?1 and enzyme activity reached 1,030 U ml?1. Purified appA-Q258N/Q349N had a specific activity of 3,137 U mg?1 with an MW of approx. 53 kDa. Compared with appA-WT, appA-Q258N/Q349N showed over 40 % enhancement in thermostability (85 °C for 10 min) and 4–5 °C increases in the melting temperatures (Tm). The Km and Kcat of appA-Q258N/Q349N were 0.43 mM and 3,058 s?1, respectively, which are similar with that of appA-WT. The mutant appA-Q258N/Q349N obtained in this study could be used for the large-scale commercial production of phytase.  相似文献   

18.
Biodegradation of pyridine by a novel bacterial strain, Rhizobium sp. NJUST18, was studied in batch experiments over a wide concentration range (from 100 to 1,000 mg l?1). Pyridine inhibited both growth of Rhizobium sp. NJUST18 and biodegradation of pyridine. The Haldane model could be fitted to the growth kinetics data well with the kinetic constants μ* = 0.1473 h?1, K s = 793.97 mg l?1, K i = 268.60 mg l?1 and S m = 461.80 mg l?1. The true μ max, calculated from μ*, was found to be 0.0332 h?1. Yield coefficient Y X/S depended on S i and reached a maximum of 0.51 g g?1 at S i of 600 mg l?1. V max was calculated by fitting the pyridine consumption data with the Gompertz model. V max increased with initial pyridine concentration up to 14.809 mg l?1 h?1. The q S values, calculated from $V_{ \hbox{max} }$ , were fitted with the Haldane equation, yielding q Smax = 0.1212 g g?1 h?1 and q* = 0.3874 g g?1 h?1 at S m′ = 507.83 mg l?1, K s′ = 558.03 mg l?1, and K i′ = 462.15 mg l?1. Inhibition constants for growth and degradation rate value were in the same range. Compared with other pyridine degraders, μ max and S m obtained for Rhizobium sp. NJUST18 were relatively high. High K i and K i′ values and extremely high K s and K s′ values indicated that NJUST18 was able to grow on pyridine within a wide concentration range, especially at relatively high concentrations.  相似文献   

19.
A rapid micropropagation system for Scabiosa tschiliensis Grunning, an ethnic medicinal plant, has been developed. Calluses were induced from leaf and petiole explants on Murashige and Skoog (MS) medium supplemented with 2.0 mg l?1 thidiazuron and 0.5 mg l?1 2,4-dicholorophenoxyacetic acid. In this medium, callus induction rate was about 94.05 %. Adventitious shoots developed from leaf (86.30 %) and petiole (83.33 %) calluses when cultured on MS medium containing 4.0 or 2.0 mg l?1 N6-benzyladenine (BA), respectively. Up to 73.85 % of the regenerated shoots formed complete plantlets on MS medium supplemented with 2.0 mg l?1 indole-3-butyric acid, with an average of 3.25 roots per shoot. Quantitative analysis of flavonoids showed that the phytochemical profiles of calluses and regenerated plants were similar to that of wild-type plants. The 2, 2-diphenyl-1-picrylhydrazyl assay revealed that the flavonoid extracts of calluses, adventitious shoots and wild-type plants had stronger antioxidant activities, the inhibitory concentrations being 23.944, 31.329 and 26.502 μg ml?1, respectively, where 50 % of DPPH was scavenged (IC50). Results showed that this perennial herb could be used as a potential source of new natural antioxidants.  相似文献   

20.
The cypress aphid (Cinara cupressi) is listed among the hundred most important invasive pests in the world. In Chile, it was first detected in 2003 and currently is present throughout the country. In the course of a survey of their natural enemies in Chile, three strains of entomopathogenic fungi were isolated. The isolates were identified and tested against the aphid in laboratory experiments. Two further entomopathogenic fungi (ARSEF 5126 and 5128), formulated in the mycoinsecticides Vertalec® and Mycotal®, were used as reference strains. The three Chilean isolates were identified genomically as Lecanicillium attenuatum and were pathogenic to third-instar nymphs. The isolate ARSEF 13279 yielded the lowest overall lethal concentration (LC50), 3 × 105 conidia ml?1 at four days post-inoculation, and the shortest lethal time (LT50), 3.7 days after inoculation with 106 conidia ml?1. The results indicate that the isolates have considerable potential as microbial control agents of the invasive cypress aphid.  相似文献   

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