Antimicrobial activity of endophytic fungi associated with halophytic species Salsola vermiculata

Endophytic fungi are known for their production of bioactive compounds with antibacterial and antifungal activity. In this study, an evaluation of the antibacterial and antifungal activity of endophytic fungi isolated from Salsola vermiculata, a halophyte species collected from Chott el Hodna, M'sila (Algeria) was carried out. The eleven isolated endophytic fungi were identified as belonging to the genera Alternaria sp., Aureobasidium sp., Phoma sp., Chrysosporium sp., Fusarium sp., Aspergillus sp., Papulaspora sp., Ulocladium sp., Humicola sp. and Pencillium sp. The antimicrobial activity of endophyte isolates was tested against phytopathogenic fungi and pathogenic bacteria using the dual culture and the agar plug diffusion methods respectively. The higher percentage inhibition of 79% was obtained by the isolate Penicillium sp. 1 against Fusarium oxysporum f.sp. ciccri. All isolated endophytic fungi showed antibacterial activity against at least one pathogenic bacterium, the greatest effect was obtained by Fusarium sp. against Pseudomonas aeruginosa ATCC 27853 and Bacillus cereus ATCC 10876 with inhibition zones of 26.33 and 25.33 mm respectively. After the comparison of the means of the zones of inhibition, the isolate Chrysosporium sp. was the most active against all pathogenic bacteria with average inhibition zones of 20.55 mm. DOI: http://dx.doi.org/10.5281/zenodo.703603

Broad antibacterial spectrum of endophytic fungi isolated from halophyte Suaeda fruticosa in Algeria

The purpose of this work was to isolate and evaluate the antimicrobial potential of endophytic fungi isolated from Suaeda fruticosa. Endophytic isolates were identified at the genus level. The genera Fusarium (33.33%), Phoma (26.67%), Penicillium (13.33%), and Aspergillus (13.33%) were more prevalent, while Trichoderma genus (6.67%) was less common. The isolated fungal endophytes were screened for their potential antifungal and antibacterial activities. Most isolates showed different levels of inhibitory activity against at least one of the pathogens. The best inhibition percentages were those obtained by Penicillium sp. 1; 74, 71, 65, and 47% against Fusarium oxysporum f.sp. albedinis, Fusarium oxysporum f.p. ciccri, Fusarium solani var. coeruleum and Phytophthora infestans respectively. Regarding antibacterial activity, the zones of inhibition ranged from 0 to 25.5 mm. Fusarium isolates and Phoma sp. 4 showed the greatest antibacterial activity, the highest activity was observed with Fusarium sp.5 and Fusarium sp. 1, which gave zones of inhibition of 25.5 and 22.5 mm respectively against B. cereus ATCC 10876. Gram-positive bacteria were more sensitive to endophyte isolates than Gram-negative bacteria. From the results of the present work, it is possible to conclude that endophytic fungi isolated from Suaeda fruticosa could be a promising source of bioactive compounds and deserve further study. DOI: http://dx.doi.org/10.5281/zenodo.702827

Indirect adaptive fuzzy finite time synergetic control for power systems

Introduction. Budget constraints in a world ravenous for electrical power have led utility companies to operate generating stations with full power and sometimes at the limit of stability. In such drastic conditions the occurrence of any contingency or disturbance may lead to a critical situation starting with poorly damped oscillations followed by loss of synchronism and power system instability. In the past decades, the utilization of supplementary excitation control signals for improving power system stability has received much attention. Power system stabilizers (PSS) are used to generate supplementary control signals for the excitation system in order to damp low-frequency oscillations caused by load disturbances or short-circuit faults. Problem. Adaptive power system stabilizers have been proposed to adequately deal with a wide range of operating conditions, but they suffer from the major drawback of requiring parameter model identification, state observation and on-line feedback gain computation. Power systems are nonlinear systems, with configurations and parameters that fluctuate with time that which require a fully nonlinear model and an adaptive control scheme for a practical operating environment. A new nonlinear adaptive fuzzy approach based on synergetic control theory which has been developed for nonlinear power system stabilizers to overcome above mentioned problems. Aim. Synergetic control theory has been successfully applied in the design of power system stabilizers is a most promising robust control technique relying on the same principle of invariance found in sliding mode control, but without its chattering drawback. In most of its applications, synergetic control law was designed based on an asymptotic stability analysis and the system trajectories evolve to a specified attractor reaching the equilibrium in an infinite time. In this paper an indirect finite time adaptive fuzzy synergetic power system stabilizer for damping local and inter-area modes of oscillations for power systems is presented. Methodology. The proposed controller design is based on an adaptive fuzzy control combining a synergetic control theory with a finite-time attractor and Lyapunov synthesis. Enhancing existing adaptive fuzzy synergetic power system stabilizer, where fuzzy systems are used to approximate unknown system dynamics and robust synergetic control for only providing asymptotic stability of the closed-loop system, the proposed technique procures finite time convergence property in the derivation of the continuous synergetic control law. Analytical proofs for finite time convergence are presented confirming that the proposed adaptive scheme can guarantee that system signals are bounded and finite time stability obtained. Results. The performance of the proposed stabilizer is evaluated for a single machine infinite bus system and for a multi machine power system under different type of disturbances. Simulation results are compared to those obtained with a conventional adaptive fuzzy synergetic controller.Вступ. Бюджетні обмеження у світі, жадібному до електроенергії, змушують комунальні підприємства експлуатувати станції, що генерують, на повну потужність, а іноді і на межі стабільності. У таких різких умовах виникнення будь-якої позаштатної ситуації або збурення може призвести до виникнення критичної ситуації, що починається з погано згасаючих коливань з подальшою втратою синхронізму та нестійкістю енергосистеми. В останні десятиліття велика увага приділялася використанню додаткових сигналів, керуючих збудження, для підвищення стійкості енергосистеми. Стабілізатори енергосистеми (СЕС) служать для вироблення додаткових сигналів керування системою збудження з метою гасіння низькочастотних коливань, спричинених збуреннями навантаження або короткими замиканнями. Проблема. Адаптивні стабілізатори енергосистем були запропоновані для того, щоб адекватно справлятися з широким діапазоном робочих умов, але вони страждають від основного недоліку, що полягає в необхідності ідентифікації моделі параметрів, спостереження за станом та обчислення коефіцієнта посилення зворотного зв'язку в режимі реального часу. Енергетичні системи є нелінійними системами з конфігураціями та параметрами, які змінюються з часом, що потребує повністю нелінійної моделі та схеми адаптивного управління для практичного операційного середовища. Новий нелінійний адаптивно-нечіткий підхід, заснований на синергетичній теорії управління, розроблений для нелінійних стабілізаторів енергосистем для подолання вищезазначених проблем. Мета. Теорія синергетичного управління успішно застосовувалася під час проєктування стабілізаторів енергосистем. Це найбільш перспективний надійний метод управління, заснований на тому ж принципі інваріантності, що і в ковзному режимі управління, але без його недоліку, пов'язаного з вібрацією. У більшості своїх програм синергетичний закон управління був розроблений на основі аналізу асимптотичної стійкості, і траєкторії системи еволюціонують до заданого атрактора, що досягає рівноваги за нескінченний час. У статті подано непрямий адаптивний нечіткий синергетичний стабілізатор енергосистеми з кінцевим часом для гасіння локальних та міжзонових мод коливань енергосистем. Методологія. Пропонована конструкція регулятора заснована на адаптивному нечіткому управлінні, що поєднує синергетичну теорію управління з атрактором кінцевого часу та синтезом Ляпунова. Удосконалюючи існуючий стабілізатор адаптивної нечіткої синергетичної енергосистеми, де нечіткі системи використовуються для апроксимації динаміки невідомої системи та надійного синергетичного управління тільки для забезпечення асимптотичної стійкості замкнутої системи, запропонований метод забезпечує властивість збіжності за кінцевий час при виведенні безперервного синергетичного закону керування. Наведено аналітичні докази збіжності за кінцевий час, що підтверджують, що запропонована адаптивна схема може гарантувати обмеженість сигналів системи та отримання стійкості за кінцевий час. Результати. Працездатність пропонованого стабілізатора оцінюється для одномашинної системи з нескінченними шинами і багатомашинної енергосистеми при різних типах збурень. Результати моделювання порівнюються з результатами, отриманими за допомогою звичайного нечіткого адаптивного синергетичного регулятора

Antimicrobial activity of potato Rhizospheric Pseudomonas chlororaphis subsp. aureofaciens from Sétif Algeria

Aims: This study was assessed to demonstrate the antimicrobial activity in vitro of an identified fluorescent Pseudomonas strain characterized for its capacity to produce phenazine compounds. Methodology: First Pseudomonas chlororaphis subsp aureofaciens was inoculated on Nutrient Broth supplemented with Yeast Extract (NBY) and with glucose at a final concentration of 2%, after incubation the filtered culture was acidified with HCl to pH 2. The solution was extracted twice with the same volume of ethyl-acetate. The organic supernatants were combined, dried over anhydrous Na2SO4, and evaporated to dryness. The crude extract was resuspended in methanol and tested for antimicrobial activity. Antimicrobial activity was determined (i) by disc diffusion technique for bacteria and (ii) using serial dilution technique in soft PDA for fungi. Secondly the antifungal activity of the bacterial strain was tested against several phytopathogenic fungi in dual culture. Results: The studied strain has an important activity against the phytopathogenic bacteria and fungi tested. Among the tested fungi Fusarium oxysporum f. sp. albedinis is the most sensitive to the actions of this Pseudomonas, where the inhibition rate reached 77.78%. The less sensitive one was Pythium ultimum with a rate of 55.56%. While for pathogenic bacteria only Salmonella enteridis was sensitive to the tested strain. Conclusion: Pseudomonas chlororaphis subsp aureofaciens showed appreciable antagonistic activity, in vitro, against special forms of Fusarium oxysporum and the tested phytopathogenic bacteria

Bacteriocins contributing in Rhizospheric competition among Fluorescent Pseudomonads

Aims: To examine the production of bacteriocins through the study of a group of rhizospheric Pseudomonas isolates already known to produce metabolites that are antagonistic to fungi. Methodology: Fourteen rhizospheric strains of fluorescent Pseudomonads spp., were tested as well as two referenced strains Pseudomonas protogens CHA0 and Pseudomonas aureofaciens 30-84, for their ability to produce induced bacteriocins. The induction is carried out first by UV light, and secondly by mitomycin C. Results: In addition to the reference strains, six isolates were found to produce bactericidal substances after UV light induction against Pseudomonas target bacteria but also against other genera (Escherichia and Staphylococcus). Producing strains were treated with mitomycin C, and then lysed with chloroform. Analysis of the lysates by trypsin and freezing treatments, suggests that the active compounds are of high molecular weight. Conclusion: It is therefore suggested that these bacteria could be good competitors for their introduction as biocontrol agents

Antimicrobial and Antioxidant Activities of Flavonoids Extracted from Pistacia lentiscus L., Leaves

Increasingly, the flavonoids becoming the subject of biomedical researches, and many groups have isolated and identified the structures of flavonoids possessing important biological activities. This assess investigates the antimicrobial fight and the antioxidant strengths of flavonoids extracted from Pistacia lentiscus L. leaves.  The extract was first analyzed for its phenolic content, then the flavonoids were tested for their antimicrobial capacities by the method of diffusion against fourteen bacteria, two fungi and one yeast. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of flavonoids were determined using the dilution method on solid medium, however, the antioxidant activity was evaluated through the ability of the extract to scavenge DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals and the reducing power essay. The results indicate that flavonoids extract contain other phenolics groups. On the other side, the Antibacterial tests exhibited different activities depending on the strains. Unlike, the MIC and the MBC showed that the flavonoids extract showed a best activity against Candida albicans and Vibrio cholerae. Concerning antioxidant activity, the results indicate a moderate capacity of the flavonoid extract. These preliminary results may justify the use of this plant in the treatment of some diseases and may be exploited for therapeutic purposes. Keywords: Antimicrobial, Antioxidant, Pistacia lentiscus, flavonoids, MIC, MBC

IN VITRO EVALUATION OF BIOLOGICAL ACTIVITIES OF PISTACIA LENTISCUS AQUEOUS EXTRACT

Objective: The aim of this study was to study the antioxidant potential and the antibacterial activity of leaves aqueous extract of Pistacia Lentiscus as well as the protective effect of this extract against the haemolysis in hypotonic condition, in oxidative stress and in the existence of saponin injury.Methods: We studied the antioxidant capacity through the DPPH assay, H2O2 scavenging activity, Ferric-reducing power (FRAP) assay, total antioxidant assay and the antibacterial activity using the disc diffusion method. We also investigated the haemolytic activity with the spectrophotometric method.Results: The result showed that the aqueous extract had a good antioxidant capacity, which was calculated as IC50. IC50 of the aqueous extract was found to be 9.89±0.7µg/ml for DPPH scavenging, 200±18.02µg/ml for H2O2 scavenging assay, 54.06±12.66µg/ml for Ferric-reducing power (FRAP) and 500±22.3 µg/ml for total antioxidant capacity. The aqueous extract also inhibited the growth of the tested bacterial strains with a maximum inhibition zone of 30.33±5.5 mm observed on Pseudomonas aeruginosa for wood-seed and a moderate activity against all other strain. The haemolytic analysis showed that the aqueous extract is not toxic for the human erythrocytes and protects them against the oxidative and osmotic stress and also against saponin injury.Conclusion: The results of our study suggest that the aqueous extract of leaves of Pistacia lentiscus possess potent anti-haemolytic activity, are a good source of natural antioxidant.Â

Indirect adaptive fuzzy finite time synergetic control for power systems

Introduction. Budget constraints in a world ravenous for electrical power have led utility companies to operate generating stations with full power and sometimes at the limit of stability. In such drastic conditions the occurrence of any contingency or disturbance may lead to a critical situation starting with poorly damped oscillations followed by loss of synchronism and power system instability. In the past decades, the utilization of supplementary excitation control signals for improving power system stability has received much attention. Power system stabilizers (PSS) are used to generate supplementary control signals for the excitation system in order to damp low-frequency oscillations caused by load disturbances or short-circuit faults. Problem. Adaptive power system stabilizers have been proposed to adequately deal with a wide range of operating conditions, but they suffer from the major drawback of requiring parameter model identification, state observation and on-line feedback gain computation. Power systems are nonlinear systems, with configurations and parameters that fluctuate with time that which require a fully nonlinear model and an adaptive control scheme for a practical operating environment. A new nonlinear adaptive fuzzy approach based on synergetic control theory which has been developed for nonlinear power system stabilizers to overcome above mentioned problems. Aim. Synergetic control theory has been successfully applied in the design of power system stabilizers is a most promising robust control technique relying on the same principle of invariance found in sliding mode control, but without its chattering drawback. In most of its applications, synergetic control law was designed based on an asymptotic stability analysis and the system trajectories evolve to a specified attractor reaching the equilibrium in an infinite time. In this paper an indirect finite time adaptive fuzzy synergetic power system stabilizer for damping local and inter-area modes of oscillations for power systems is presented. Methodology. The proposed controller design is based on an adaptive fuzzy control combining a synergetic control theory with a finite-time attractor and Lyapunov synthesis. Enhancing existing adaptive fuzzy synergetic power system stabilizer, where fuzzy systems are used to approximate unknown system dynamics and robust synergetic control for only providing asymptotic stability of the closed-loop system, the proposed technique procures finite time convergence property in the derivation of the continuous synergetic control law. Analytical proofs for finite time convergence are presented confirming that the proposed adaptive scheme can guarantee that system signals are bounded and finite time stability obtained. Results. The performance of the proposed stabilizer is evaluated for a single machine infinite bus system and for a multi machine power system under different type of disturbances. Simulation results are compared to those obtained with a conventional adaptive fuzzy synergetic controller

Chemical composition and antibacterial activity of Algerian propolis against fish pathogenic bacteria

Five different varieties of propolis from four sites from Sétif region (East of Algeria) (Babor, Setif; Ain-Abbassa and El-Hamma), and one site from the center of Algeria (Tizi-Ouzou) were chemically analysed by gas chromatography-mass spectrometry. One hundred and two compounds were identified including aromatic acids, linear hydrocarbons and their acids, terpenes and alcaloïdes. Furthermore, the in vitro bacteriostatic and bactericidal activities of the aqueous extracts were evaluated against one Gram positive (Bacillus subtilis, used as probiotics in aquaculture) and two Gram negative (Vibrio anguillarum and Vibrio harveyi, pathogenic for fish) bacteria. The obtained results showed that all aqueous extracts of propolis inhibit the growth of B. Subtilis while the growth inhibition of fish pathogens was achieved when using higher propolis concentrations. These antibacterial properties would warrant further studies on the clinical applications of propolis in aquaculture field. Keywords: Bactericidal activity; Chemical characterization; Propolis; Vibrio