Novel biosynthesis,characterization and bio-catalytic potential of green algae (Spirogyra hyalina) mediated silver nanomaterials

In recent years green nanotechnology gained significant importance to synthesize nanoparticles due to their cost effectiveness and biosafety. In the current study, silver nanoparticles were synthesized by using extract of Spirogyra hyalina as a capping and reducing agent. The synthesized nanoparticles were characterized by UV–Visible spectroscopy, Fourier transform infrared spectroscopy, Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractive analysis. Silver nanoparticles give a characteristic Surface Plasmon Resonance peak of 451 nm at 2.21 a.u (arbitrary unit). SEM micrograph revealed the spherical morphology and average grain size of 52.7 nm. Furthermore, antibacterial, antifungal, insecticidal, antioxidant and membrane damage activities were determined. The maximum antibacterial and antifungal activity was observed for Pseudomonas aeruginosa (18 ± 1.2 mm) and Fusarium solani (14.3 ± 0.6 mm), respectively. In membrane damage assay, Pseudomonas aeruginosa absorbed A₂₆₀ wavelength and gave maximum peak values of 0.286, 0.434 and 0.629 at 25, 35 and 45 µg/mL of silver nanoparticles. The membrane damage assay confirmed that nanoparticles are involved in bacterial cell membrane damage. At 500 ppm silver nanoparticles showed 30% mortality against Tribolium castaneum (a common grain pest). The silver nanoparticles also showed potent antioxidant activity and successfully scavenged the DPPH free radicals upto 53.43 ± 0.17, 43.26 ± 0.97, 31.39 ± 0.33, 24.62 ± 0.85, and 14.13 ± 0.12% at a concentration of 400, 200, 100, 50, and 25 µg/mL of nanoparticles, respectively. It is concluded that silver nanoparticles can easily be synthesized by using green algae Spirogyra hyalina as a capping and reducing agent. Silver nanoparticles showed potent biomedical activities and thus can be used for therapeutic applications invitro and invivo.     

Silver nanostructures prepared via novel green approach as an effective platform for biological and environmental applications

Silver nanoparticles play a significant role in biomedical sciences due to their unique properties allowing for their use as an effective sensing and remediation platform Herein, the green synthesis of silver nanostructures (Ag NSs), prepared via aqueous extract of waste Brassica oleracea leaves in the presence of silver nitrate solution (10^-4 M), is reported. The Ag NSs are fully characterized and their efficacy with respect to 4-nitrophenol reduction, glucose sensing, and microbes is determined. Visually, the color of silver nitrate containing solution altered from colorless to yellowish, then reddish grey, confirming the formation of Ag NSs. HRTEM and SEAD studies revealed the Ag NSs to have different morphologies (triangular, rod-shaped, hexagonal, etc., within a size range of 20–40 nm) with face-centered cubic (fcc) crystal structure. The Ag NSs possess high efficacy for nitrophenol reduction (<11 min and degradation efficiency of 98.2%), glucose sensing (LOD: 5.83 µM), and antimicrobial activity (E. coli and B. subtilis with clearance zones of 18.3 and 14 mm, respectively). Thus, the current study alludes towards the development of a cost-effective, sustainable, and efficient three-in-one platform for biomedical and environmental applications.     

Synthesis,characterization and evaluation of antimicrobial and cytotoxic activities of biogenic silver nanoparticles synthesized from <Emphasis Type="Italic">Streptomyces xinghaiensis</Emphasis> OF1 strain

We report synthesis of silver nanoparticles (AgNPs) from Streptomyces xinghaiensis OF1 strain, which were characterised by UV–Vis and Fourier transform infrared spectroscopy, Zeta sizer, Nano tracking analyser, and Transmission electron microscopy. The antimicrobial activity of AgNPs alone, and in combination with antibiotics was evaluated against bacteria, namely Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis, and yeasts viz., Candida albicans and Malassezia furfur by using micro-dilution method. The minimum inhibitory concentration (MIC) and minimum biocidal concentration of AgNPs against bacterial and yeast strains were determined. Synergistic effect of AgNPs in combination with antibacterial and antifungal antibiotics was determined by FIC index. In addition, MTT assay was performed to study cytotoxicity of AgNPs alone and in combination with antibiotics against mouse fibroblasts and HeLa cell line. Biogenic AgNPs were stable, spherical, small, polydispersed and capped with organic compounds. The variable antimicrobial activity of AgNPs was observed against tested bacteria and yeasts. The lowest MIC (16 µg ml^?1) of AgNPs was found against P. aeruginosa, followed by C. albicans and M. furfur (both 32 µg ml^?1), B. subtilis and E. coli (both 64 µg ml^?1), and then S. aureus and Klebsiella pneumoniae (256 µg ml^?1). The high synergistic effect of antibiotics in combination with AgNPs against tested strains was found. The in vitro cytotoxicity of AgNPs against mouse fibroblasts and cancer HeLa cell lines revealed a dose dependent potential. The IC₅₀ value of AgNPs was found in concentrations of 4 and 3.8 µg ml^?1, respectively. Combination of AgNPs and antibiotics significantly decreased concentrations of both antimicrobials used and retained their high antibacterial and antifungal activity. The synthesis of AgNPs using S. xinghaiensis OF1 strain is an eco-friendly, cheap and nontoxic method. The antimicrobial activity of AgNPs could result from their small size. Remarkable synergistic effect of antibiotics and AgNPs offer their valuable potential in nanomedicine for clinical application as a combined therapy in the future.     

Silver glyconanoparticles functionalized with sugars of sweet sorghum syrup as an antimicrobial agent

Bio-directed synthesis of metal nanoparticles is gaining importance due to their biocompatibility, low toxicity and eco-friendly nature. We used sweet sorghum syrup for a facile and cost-effective green synthesis of silver glyconanoparticles. Silver nanoparticles were formed due to reduction of silver ions when silver nitrate solution was treated with sorghum syrup solutions of different pH values. The nanoparticles were characterized by UV–vis, TEM (transmission electron microscopy), DLS (dynamic light scattering), EDAX (energy dispersive X-ray spectroscopy), FT-IR (fourier transform infrared spectroscopy) and XRD (X-ray diffraction spectroscopy). The silver glyconanoparticles exhibited a characteristic surface plasmon resonance around 385 nm. At pH 8.5, the nanoparticles were mono-dispersed and spherical in shape with average particle size of 11.2 nm. The XRD and SAED studies suggested that the nanoparticles were crystalline in nature. EDAX analysis showed the presence of elemental silver signal in the synthesized glyconanoparticles. FT-IR analysis revealed that glucose, fructose and sucrose present in sorghum syrup acted as capping ligands. Silver glyconanoparticles prepared at pH 8.5 had a zeta potential of ?28.9 mV and were anionic charged. They exhibited strong antimicrobial activity against Gram-positive, Gram-negative and different Candida species at MIC values ranging between 2 and 32 μg ml^?1. This is first report on sweet sorghum syrup sugars-derived silver glyconanoparticles with antimicrobial property.     

Development and characterization of a carvacrol nanoemulsion and evaluation of its antimicrobial activity against selected food-related pathogens

Carvacrol has been recognized as an efficient growth inhibitor of food pathogens. However, carvacrol oil is poorly water-soluble and can be oxidized, decomposed or evaporated when exposed to the air, light, or heat. To overcome these limitations, a carvacrol nanoemulsion was developed and its antimicrobial activity against food pathogens evaluated in this study. The nanoemulsion containing 3% carvacrol oil, 9% surfactants (HLB 11) and 88% water, presented good stability over a period of 90 days. In general, the carvacrol nanoemulsion (MIC: 256 µg ml⁻¹ for E. coli and Salmonella spp., 128 µg ml⁻¹ for Staphylococcus aureus and Pseudomonas aeruginosa) exhibited improved antimicrobial activity compared to the free oil. The carvacrol nanoemulsion additionally displayed bactericidal activity against Escherichia coli, P. aeruginosa and Salmonella spp. Therefore, the results of this study indicated that carvacrol oil nanoemulsions can potentially be incorporated into food formulations, wherein their efficacy for the prevention and control of microbial growth could be evaluated.     

Combination of antibiotics and chitin synthesis inhibitors for the control of Microcerotermes diversus (Isoptera: Termitidae)

The symbiotic microorganisms in the gut of termites play a key role in the digestion of cellulose and nitrogen metabolism. Therefore, disruption of these symbioses activity can open a door toward termite management. Thus, the current study aimed to exploit termite gut bacterial capacity in order to utilize it for efficient termite control. So, in the current study, gut bacteria of Microcerotermes diversus have been extracted, cultivated on both liquid and solid media, and screened with a range of antibiotics to find the most effective antibiotics. Results showed that chloramphenicol and nalidixic acid were the most effective antibiotics in preventing the colony unit formation of the gut bacteria amongst 16 antibiotics tested. Also, from two chitin synthesis inhibitors tested hexaflumuron with an LC₅₀ of 613.9 µg ml⁻¹ was more toxic than lufenuron with an LC₅₀ of 1414.5 µg ml⁻¹. Thus, two antibiotics (chloramphenicol and nalidixic acid) were used simultaneously with a sub-lethal concentration of hexaflumuron against the termite and a variety of factors such as wood consumption rate, running speed, body water content, and tunneling activity were evaluated under laboratory conditions. Results showed that the combination of these two antibiotics (chloramphenicol and nalidixic acid) with hexaflumuron caused a significant decrease in termite consumption rate, running speed, and tunneling behavior, but didn’t affect the body water contents of termites. These results suggest that using a combination of antibiotic/s and hexaflumuron is a promising management practice to get a suitable control measure for the studied termite.     

Antimicrobial activity and cytotoxicity trait of a bioactive peptide purified from Lactococcus garvieae subsp. bovis BSN307T

A bioactive peptide of 8595 Da was purified from the cell free supernatant of Lactococcus garvieae subsp. bovis BSN307^T. MALDI MS/MS peptide mapping and the data base search displayed no significant similarity to any reported antimicrobial peptide of LAB. This peptide at a dose concentration of 200 µg ml⁻¹ inhibited the growth of both Gram-positive and Gram-negative bacteria by 58–89% and a dose of 500 µg ml⁻¹ scavenged 50% of DPPH-free radicals generated. Interestingly, cytotoxicity assay demonstrated that 17 µg ml⁻¹ of peptide selectively inhibited 50% proliferation of mammalian cancer cell lines HeLa and MCF-7 whereas normal H9c2 cells remained unaffected. Fluorescent microscopic analysis after DAPI nuclear staining of HeLa cells showed characteristics of apoptosis and activation of caspase-3 was ascertained by caspase-3 fluorescence assay.     

Synergistic Impact of Phosphate Solubilizing Bacteria and Phosphorus Rates on Growth,Antioxidative Defense System,and Yield Characteristics of Upland Rice (Oryza sativa L.)

In the present study, we examined the synergistic effect of phosphate solubilizing bacteria (PSB) and the chemical phosphate on the growth, photosynthetic efficiency, phosphorus (P) uptake, antioxidant activity, and yield of upland rice. Three effective bacterial strains with potent P solubilizing activity viz., Bacillus licheniformis (688.18 µg ml^?1), Pantoea dispersa (570.90 µg ml^?1), and Staphylococcus sp. (551.81 µg ml^?1), were isolated from rice rhizosphere to study their impact on upland rice growth and yield under field conditions for two consecutive years. The experiment data revealed significant increments in shoot height, shoot dry weight, total chlorophyll, carotenoid, chlorophyll fluorescence (fv/fm), P uptake, antioxidant activity, and yield characteristics in upland rice treated with individual PSB or their consortia alone, compared to uninoculated control. However, the integrated use of PSB with 50% recommended P dose showed maximum increment in growth indices (21.25%, 21.86% increase in shoot length and 87.18%, 97.06% increase in shoot dry weight), P uptake (110.37%, 122.78% increase), and yield (50.58%, 35.64% increase) compared to uninoculated control for 2018 and 2019, respectively, indicating a reduction in the dependence of chemical P fertilizer by 50%. Therefore, it can be concluded that combined application of PSB and 50% recommended dose of chemical P can be implied for the sustainable cultivation of upland rice systems to give maximum benefits to the farmers and the environment.

     

Pharmacological properties of biogenically synthesized silver nanoparticles using endophyte Bacillus cereus extract of Berberis lyceum against oxidative stress and pathogenic multidrug-resistant bacteria

The emergence of multidrug resistance in pathogenic bacteria limits the utilization of available antibiotics. The development of alternate options to treat infectious diseases is the need of the day.The present study was aimed to synthesize, characterize and evaluate the bioactive properties of silver nanoparticles. Endophytic bacterium Bacillus cereus (MT193718) isolated from Berberis lycium was used to synthesize biocompatible silver nanoparticles. Antibacterial properties of AgNPs were evaluated against clinically isolated multidrug-resistant strains of Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae. AgNPs indicated significant antibacterial activity against S. aureus and K. pneumoniae fwith a zone of inhibition of 17 and 18 mm at a concentration of 1000 µg/ mL with minimum inhibitory concentration of 15.6 and 62.5 µg/mL respectively. Significant antioxidant activity with an IC50 value of 9.5 µg/mL was recorded. Biosynthesized AgNPs were found compatible with red blood cells at a concentration of 31.5 µg/ml with no clumping of erythrocytes. The study suggested that AgNPs synthesized by the endophytic bacterium Bacillus cereus are biologically active and can be used as antioxidant and antibacterial agents against drug-resistant bacteria.     

Sequential interactions of silver–silica nanocomposite (Ag–SiO2NC) with cell wall,metabolism and genetic stability of Pseudomonas aeruginosa,a multiple antibiotic‐resistant bacterium

The study was carried out to understand the effect of silver–silica nanocomposite (Ag–SiO₂NC) on the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, a multiple drug‐resistant bacterium. Bacterial sensitivity towards antibiotics and Ag–SiO₂NC was studied using standard disc diffusion and death rate assay, respectively. The effect of Ag–SiO₂NC on cell wall integrity was monitored using SDS assay and fatty acid profile analysis, while the effect on metabolism and genetic stability was assayed microscopically, using CTC viability staining and comet assay, respectively. Pseudomonas aeruginosa was found to be resistant to β‐lactamase, glycopeptidase, sulfonamide, quinolones, nitrofurantoin and macrolides classes of antibiotics. Complete mortality of the bacterium was achieved with 80 μg ml^?1 concentration of Ag–SiO₂NC. The cell wall integrity reduced with increasing time and reached a plateau of 70% in 110 min. Changes were also noticed in the proportion of fatty acids after the treatment. Inside the cytoplasm, a complete inhibition of electron transport system was achieved with 100 μg ml^?1 Ag–SiO₂NC, followed by DNA breakage. The study thus demonstrates that Ag–SiO₂NC invades the cytoplasm of the multiple drug‐resistant P. aeruginosa by impinging upon the cell wall integrity and kills the cells by interfering with electron transport chain and the genetic stability.

Significance and Impact of Study

Although the synthesis, structural characteristics and biofunction of silver nanoparticles are well understood, their application in antimicrobial therapy is still at its infancy as only a small number of microorganisms are tested to be sensitive to nanoparticles. A thorough knowledge of the mode of interaction of nanoparticles with bacteria at subcellular level is mandatory for any clinical application. The present study deals with the interactions of Ag–SiO2NC with the cell wall integrity, metabolism and genetic stability of Pseudomonas aeruginosa, which would contribute substantially in strengthening the therapeutic applications of silver nanoparticles.     

Heteroresistance to the model antimicrobial peptide polymyxin B in the emerging Neisseria meningitidis lineage 11.2 urethritis clade: mutations in the pilMNOPQ operon

Clusters of Neisseria meningitidis (Nm) urethritis among primarily heterosexual males in multiple US cities have been attributed to a unique non‐encapsulated meningococcal clade (the US Nm urethritis clade, US_NmUC) within the hypervirulent clonal complex 11. Resistance to antimicrobial peptides (AMPs) is a key feature of urogenital pathogenesis of the closely related species, Neisseria gonorrhoeae. The US_NmUC isolates were found to be highly resistant to the model AMP, polymyxin B (PmB, MICs 64–256 µg ml^–1). The isolates also demonstrated stable subpopulations of heteroresistant colonies that showed near total resistant to PmB (MICs 384–1024 µg ml^–1) and colistin (MIC 256 µg ml^–1) as well as enhanced LL‐37 resistance. This is the first observation of heteroresistance in N. meningitidis. Consistent with previous findings, overall PmB resistance in US_NmUC isolates was due to active Mtr efflux and LptA‐mediated lipid A modification. However, whole genome sequencing, variant analyses and directed mutagenesis revealed that the heteroresistance phenotypes and very high‐level AMP resistance were the result of point mutations and IS1655 element movement in the pilMNOPQ operon, encoding the type IV pilin biogenesis apparatus. Cross‐resistance to other classes of antibiotics was also observed in the heteroresistant colonies. High‐level resistance to AMPs may contribute to the pathogenesis of US_NmUC.     

Enhancement of production and activity of alkaline zinc metalloprotease from <Emphasis Type="Italic">Salinivibrio proteolyticus</Emphasis> using low intensity direct electric current and zinc nanoparticles

Objectives

To improve the production and activity of an alkaline zinc metalloprotease from Salinivibrio proteolyticus in response to ZnSO₄ (ionic and nanoparticle forms) and low intensity direct electric current (LIDC).

Results

A DC of 50 µA for 10 min increased enzyme production from 35 to 53 U ml^?1 when applied to the stationary phase bacterial cells. Zn²⁺ improved enzyme production better than zinc nanoparticles (52 vs. 43.5 U ml^?1). Zinc nanoparticles (0.5 mM) added to an enzyme reaction mixture containing casein (0.65 %) and 20 mM Tris/HCl buffer (pH 8) improved enzyme activity more than Zn²⁺ (42 vs. 36 U ml^?1).

Conclusion

LIDC exposure (50 µA, 10 min) to the stationary phase bacterial cells increases metalloprotease production in Salinivibrio. A low concentration of zinc nanoparticles (0.5 mM) increases maximum enzyme activity.

     

Antibiofilm and antifungal activities of medium-chain fatty acids against Candida albicans via mimicking of the quorum-sensing molecule farnesol

Candida biofilms are tolerant to conventional antifungal therapeutics and the host immune system. The transition of yeast cells to hyphae is considered a key step in C. albicans biofilm development, and this transition is inhibited by the quorum-sensing molecule farnesol. We hypothesized that fatty acids mimicking farnesol might influence hyphal and biofilm formation by C. albicans. Among 31 saturated and unsaturated fatty acids, six medium-chain saturated fatty acids, that is, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid and lauric acid, effectively inhibited C. albicans biofilm formation by more than 75% at 2 µg ml⁻¹ with MICs in the range 100–200 µg ml⁻¹. These six fatty acids at 2 µg ml⁻¹ and farnesol at 100 µg ml⁻¹ inhibited hyphal growth and cell aggregation. The addition of fatty acids to C. albicans cultures decreased the productions of farnesol and sterols. Furthermore, down-regulation of several hyphal and biofilm-related genes caused by heptanoic or nonanoic acid closely resembled the changes caused by farnesol. In addition, nonanoic acid, the most effective compound diminished C. albicans virulence in a Caenorhabditis elegans model. Our results suggest that medium-chain fatty acids inhibit more effectively hyphal growth and biofilm formation than farnesol.     

Antifungal activity of streptavidin C1 and C2 against pathogens causing Fusarium wilt

Fusarium wilt is caused by the soil-inhabiting fungus Fusarium oxysporum ff. spp. and is one of the most devastating plant diseases, resulting in losses and decreasing the quality and safety of agricultural crops. We recently reported the structures and biochemical properties of two biotin-binding proteins, streptavidin C1 and C2 (isolated from Streptomyces cinnamonensis strain KPP02129). In the present study, the potential of the biotin-binding proteins as antifungal agent for Fusarium wilt pathogens was investigated using recombinant streptavidin C1 and C2. The minimum inhibitory concentration of streptavidin C2 was found to be 16 µg ml^–1 for inhibiting the mycelial growth of F. oxysporum f.sp. cucumerinum and F. oxysporum f.sp. lycopersici, while that of streptavidin C1 was found to be 64 µg ml^–1. Compared with the nontreated control soil, the population density of F. oxysporum f.sp. lycopersici in the soil was reduced to 49·5% and 39·6% on treatment with streptavidin C1 (500 µg ml^–1) and C2 (500 µg ml^–1), respectively. A greenhouse experiment revealed that Fusarium wilt of tomato plants was completely inhibited on soil drenching using a 50-ml culture filtrate of the streptavidin-producing strain KPP02129.     

The Interactive Effect of Selenium and Farmyard Manure on Soil Microbial Activities,Yield and Selenium Accumulation by Wheat (Triticum aestivum L.) Grains

This study assessed the interactive effect of selenium (Se) and farmyard manure (FYM) on soil microbial activities, growth, yield, and Se accumulation by wheat grains. Preliminarily, the effect of Se (0–250 µg kg^?1 soil) and FYM (0–12.5 g kg^?1 soil) was assessed on soil microflora. Selenium exhibited an adverse impact on soil microflora; respiration was decreased at?≥?10 µg kg^?1 soil while dehydrogenase and urease activities were decreased at?≥?125 µg kg^?1 soil. At 250 µg Se kg^?1 soil, respiration, dehydrogenase and urease activities were decreased by 81, 40 and 35%, respectively, on unamended soil, and by 9, 47 and 22%, respectively, on FYM-amended soil. The subsequent plant experiments were conducted with same Se and FYM rates; one was harvested 42 days after sowing and other at crop maturity. The application of 125 µg Se kg^?1 and 12.5 g FYM kg^?1 soil improved seedling biomass by 12.6 and 22%, respectively, while their combined use lacked synergistic effect. Similarly, at maturity Se and FYM increased grain yield while their combined effect was not synergistic. The Se-induced suppression in microbial activities was not related to yield which was improved (11% at the highest rate in unamended soil) by Se application. Selenium application increased grain Se content in a rate-dependent manner, it increased from 0 to 1025 µg kg^?1 by applying 250 µg Se kg^?1 soil. Moreover, FYM application decreased Se accumulation in grains. It is concluded that FYM application increased soil microbial activities and yield but reduced grain Se accumulation in wheat on Se-applied soil.

     

Green synthesis of zinc oxide nanoparticles using Anoectochilus elatus,and their biomedical applications

Zinc and its derivatives requirement increased to enhance human immunity against the different pandemics, including covid-19. Green synthesis is an emerging field of research. Zinc oxide (ZnO) nanoparticles have been prepared from Anoectochilus elatus and characterized using absorption, vibrational and electron microscope analysis. They were carried for antibacterial, inflammatory control tendency, and potential antioxidant activities. The brine shrimp lethal assay tested the biologically derived nanomaterial toxicity and the lethal concentration (LC₅₀) is 599.79 µg/ml. The inhibition against the important disease-causing pathogens was measured against four-gram negative, gram-positive bacteria and two fungus pathogens. The nanomaterial exposed inhibition zone for gram-positive bacteria between 17 mm and 25 mm. The inhibition zone against gram-negative bacteria exists between 19 mm and 24 mm. The anti-inflammatory activity was assessed by inhibition of protein denaturation and protease inhibitory activity using nanomaterial. The antioxidant activity was examined using four assays for the therapeutic activities. The average size range of 60–80 nm nanoparticles has prepared and exposed the good biological activity between 50 µg/ml and 100 µg/ml. The comparative results of anti-inflammatory and antioxidant assay results with standards such as Aspirin and vitamin C exposed that two to three times higher concentrations are required for the fifty percent of inhibitions. The prepared low-cost nanoparticle has exhibited excellent biological activity without any side effects and may enhance immunity.     

Anticancer,antimicrobial, antioxidant,and catalytic activities of green-synthesized silver and gold nanoparticles using Bauhinia purpurea leaf extract

The synthesis of metal nanoparticles by green methods attained enormous attention in recent years due to its easiness, non-toxicity, and eco-friendly nature. In the present study, noble metal nanoparticles such as silver and gold were prepared using an aqueous leaf extract of a medicinal plant, Bauhinia purpurea. The leaf extract performed as both reducing and stabilizing agents for the development of nanoparticles. The formations of silver and gold nanoparticles were confirmed by observing the surface plasmon resonance peaks at 430 nm and 560 nm, respectively, in UV–Vis absorption spectrum. Various properties of nanoparticles were demonstrated using the characterization techniques such as FTIR, XRD, TEM, and EDX. The synthesized silver and gold nanoparticles had a momentous anticancer effect against lung carcinoma cell line A549 in a dose-dependent manner with IC₅₀ values of 27.97 µg/mL and 36.39 µg/mL, respectively. The antimicrobial studies of synthesized nanoparticles were carried out by agar well diffusion method against six microbial strains. Silver and gold nanoparticles were also showed high antioxidant potentials with IC₅₀ values of 42.37 µg/mL and 27.21 µg/mL, respectively; it was measured using DPPH assay. Additionally, the nanoparticles were observed to be good catalysts for the reduction of organic dyes.

     

Durability of rubberwood (Hevea brasiliensis) treated with peppermint oil,eucalyptus oil,and their main components

Anti-fungal activities of two essential oils (peppermint oil and eucalyptus oil) and their main components (menthol and eucalyptol, respectively) against molds (Aspergillus niger, Penicillium chrysogenum, and Penicillium sp.) and a white-rot decay fungus (Trametes versicolor) identified from rubberwood surfaces were investigated. The broth dilution method and the agar diffusion technique were employed to determine the minimal inhibitory concentration (MIC) and the minimal fungicidal concentration (MFC) using the concentration of substances between 100 and 800 μl ml^?1. Inhibitory effects of essential oils and their main components at the MICs against mold growth, fungal decay, and termite attack on rubberwood were further examined by means of the dip treatment method. It was found that MFC values against molds for all treatments examined were about 50–100 μl ml^?1 higher than MIC values. Peppermint oil and menthol exhibited high fungistatic and fungicidal activities, with MICs of 300 μl ml^?1 and 350 μl ml^?1, respectively, against the test molds and the decay fungus. Eucalyptus oil and eucalyptol were also effective against these microbes but at higher concentrations of 600 μl ml^?1 and 500 μl ml^?1, respectively. Only peppermint oil at the MIC was capable of providing a complete protection from mold growth on rubberwood for up to 12 weeks at storage conditions of 25 °C and 100% RH. Both peppermint oil and eucalyptus oil at the MICs showed moderate resistance to fungal decay and high resistance to termite attack.     

Performance of polymyxin B agar-based tests among carbapenem-resistant Enterobacterales

Therapeutic options for infections caused by Carbapenem-resistant Enterobacterales (CRE) are restricted and include polymyxins-centred schemes. Evaluation of in vitro susceptibility is difficult and time consuming. Agar-based methodologies are an alternative to broth microdilution (BMD) and we aimed to evaluate the accuracy of those methods among Enterobacterales. A total of 137 non-duplicated CRE were subjected to polymyxin B BMD, agar screening test (Mueller Hinton plates containing 3 µg ml⁻¹ of polymyxin B) and agar dilution (antibiotic serially diluted 0·25–64 µg ml⁻¹). CRE of 42·3% were resistant to polymyxin B (MICs range: 0·25–>64 µg ml⁻¹) and 16·8% presented borderline MICs. Sensitivity, specificity, PPV and NPV were 86·2, 98·7, 98 and 90·7% for screening test and 86·2, 97·5, 96·1 and 90·6% for agar dilution. ME was 0·73 and 1·5% for screening and agar dilution respectively; VME was 5·8% for both techniques. In general, agar-based methods had a good performance. As far as we know, this is the first study to propose an agar screening test using polymyxin B instead of colistin.     

Biodiesel synthesis from Chlorella vulgaris under effect of nitrogen limitation,intensity and quality light: estimation on the based fatty acids profiles

Cultures under nitrogen limitation for Chlorella vulgaris were kept under different light quality (white, blue, yellow and violet) at 70 and 140 µE m^?2 s^?1; to evaluate the effect on fatty acids profiles and biodiesel quality. The results showed a maximum biomass and cell density at 140 µE m^?2 s^?1 of: white light (0.69 g L^?1 and 6.5?×?10⁶ cells mL^?1, respectively) and blue light (0.65 g L^?1 and 8.0?×?10⁶ cells mL^?1, respectively); compared to violet and yellow light. The chlorophyll concentration (µg mg^?1 biomass dry weight) at 70 µE m^?2 s^?1 were in the order of light: white (25.61)?>?violet (17.10)?>?yellow (11.68)?>?blue (11.40) and, at 140 µE m^?2 s^?1 were: violet (23.64)?>?white (10.20)?>?yellow (9.66)?>?blue (7.99), suggesting the violet light stimulates the increase of chlorophyll a at higher intensity. The maximum lipid content (% w/w) were present under blue light (43.11), yellow (70.92) and violet (83.87) at 140 µE m^?2 s^?1. The different wavelengths did not have a negative effect on the quality of the biodiesel, however; violet light presented greater productivity and the indicators such as CFPP were related to the oxidative stability value and low PUFA content, leading biodiesel to good oxidative stability.