Proficient mycogenic synthesis of silver nanoparticles by soil derived fungus Aspergillus melleus SSS-10 with cytotoxic and antibacterial potency.

The present study aimed at evaluating the extracellular synthesis of silver nanoparticles by soil fungus Aspergillus melleus SSS-10 for antibacterial and cytotoxic activity. In this study, the formation of silver nanoparticles (AgNPs) was estimated by the colour change in cell free extract from pale yellow to golden yellow after 24 h of the reaction. UV-Vis study showed the absorbance maxima at 410 nm. Tauc plot analysis revealed the band gap energy as 2.34 eV. Dynamic Light Scattering (DLS) data revealed polydisperse anisotropic silver nanoparticles with average hydrodynamic diameter of 92.006 nm. Zeta potential of - 19.6 mV provided evidence of stable silver nanoparticles. X-ray diffraction (XRD) analysis revealed four prominent Bragg peaks corresponding to (111), (200), (220) and (311) planes characteristic of silver (Ag) in FCC structural configuration. Average crystallite size was found to be 87.3 nm from Scherrer equation. Scanning Electron Microscope (SEM) analysis revealed irregular morphology of silver nanoparticles. EDS analysis displayed characteristic energy peaks of silver from 2.72 keV to 3.52 keV confirming the presence of silver nanoparticles. Biosynthesized AgNPs exhibited strong cytotoxic potential on MG-63 cells. AgNPs also showed antibacterial activity against both Staphylococcus aureus and Escherichia coli. In conclusion, this study provides a platform to explore the utility of fungal mediated silver nanoparticles synthesized for various pharmaceutical and cosmeceutical applications.

Antioxidant and Anti-inflammatory Metabolites of a Soil-Derived Fungus Aspergillus arcoverdensis SSSIHL-01.

Soil houses a vast array of microbial diversity. Cultured soil microbes have been a good source of many commercial drugs. In the present study, a fungal culture (SSSIHL-01) isolated from soil has been identified as Aspergillus arcoverdensis through morphology and ITS gene sequence. Extracellular culture extract and mycelial extract of the strain SSSIHL-01 were obtained using specific conditions and were evaluated for antioxidant and anti-inflammatory activities. Culture extract at 700 µg/mL concentration, showed strong DPPH free radical scavenging capacity with 95.06% comparable with the standard ascorbic acid. At 1 mg/mL concentration, mycelial extract inhibited heat induced Bovine Serum Albumin denaturation of about 31.54% compared to that of 51% produced by the standard diclofenac sodium. Chemical profiling of both the culture and mycelial extracts were investigated using gas chromatography-mass spectrometry. Some of the major compounds identified from the culture extract were 2,4-ditert-butylphenol, 1-heptacosanol, 1-octadecene, 1-nonadecene that are known to be antioxidative. Mycelial extract presented some major compounds such as ethyl linoleate, oleic acid, n-hexadecanoic acid and ethyl palmitate that are reported to exhibit anti-inflammatory activity. Thus, our study highlights the significance of Aspergillus arcoverdensis as an effective producer of antioxidant and anti-inflammatory compounds for future utility in pharmaceutical and cosmeceutical applications.

Dye reduction-based electron-transfer activity monitoring assay for assessing microbial electron transfer activity of microbial fuel cell inocula.

Microbial fuel cells (MFC) utilize microbes as catalysts to convert chemical energy to electricity. Inocula used for MFC operation must therefore contain active microbial population. The dye reduction-based electron-transfer activity monitoring (DREAM) assay was employed to evaluate different inocula used in MFCs for their microbial bioelectrical activity. The assay utilizes the redox property of Methylene Blue to undergo color change from blue to colorless state upon microbial reduction. The extent of Methylene Blue reduction was denoted as the DREAM assay coefficient. DREAM assay was initially performed on a microbial culture along with the growth curve and estimation of colony forming units (CFUs). DREAM coefficient correlated to the CFU/mL obtained over time as growth progressed. The assay was then extended to water samples (domestic sewage, lake and a man-made pond) serving as inocula in MFCs. Domestic wastewater gave the highest DREAM coefficient (0.300 ± 0.05), followed by pond (0.224 ± 0.07) and lake (0.157 ± 0.04) water samples. Power density obtained conformed to the DREAM coefficient values, with the three samples generating power densities of 46.45 ± 5.1, 36.12 ± 3.2 and 25.08 ± 4.3 mW/m2 respectively. We have also studied the role of addition of various carbon sources and their concentrations towards improving the sensitivity of the assay. The DREAM assay is a rapid, easy-to-perform and cost-effective method to assess inocula for their suitability as anolytes in terms of electron transfer potential in MFCs.

Screening sediment samples used as anolytes in microbial fuel cells for microbial electron transfer activity using DREAM assay.

OBJECTIVE: The dye reduction-based electron-transfer activity monitoring (DREAM) assay was employed to screen sediment and wastewater samples functioning as anolytes in a microbial fuel cell (MFC) for their microbial electron transfer activity. RESULTS: Electron transfer to redox dyes from microbial activity reduced the dyes and the resulting extent of reduction was measured as DREAM assay coefficient. Methylene blue was decolourised, while resazurin underwent florigenic change from blue to pink to colourless upon formation of resorufin and dihydroxyresorufin. DREAM assay coefficient conformed to power density obtained in the MFC. A correlation was observed between chemical oxygen demand of the sample and the DREAM coefficient (+ 0.934) and also between DREAM coefficient and power density generated (+ 0.976). Highest DREAM coefficient and power density was observed for activated sludge. CONCLUSIONS: The DREAM assay is a rapid, sensitive and low-cost method to assess microbial electron transfer activity for inocula used as anolytes in a MFC.

An improvised microtiter dish biofilm assay for non-invasive biofilm detection on microbial fuel cell anodes and studying biofilm growth conditions.

Microbial life is predominantly observed as biofilms, which are a sessile aggregation of microbial cells formed in response to stress conditions. The microtiter dish biofilm formation assay is one of the most important methods of studying biofilm formation. In this study, the assay has been improvised to allow easy detection of biofilm formation on different substrata. The method has then been used to study growth conditions that affect biofilm formation, viz., the effect of pH, temperature, shaking conditions, and the carbon source provided. Glass, cellulose acetate, and carbon cloth materials were used as substrata to study biofilm development under the above conditions. The method was then extended to determine biofilm formation on the anodes of a microbial fuel cell in order to study the effect of biofilm formation on power production. A high correlation was observed between biofilm formation and power density (r = 0.951). When the electrode containing a biofilm was replaced with another electrode without biofilm, the average power density dropped from 59.55 to 5.76 mW/m2. This method offers an easy way to study the suitability of different materials to support biofilm formation. Growth conditions determining biofilm formation can be studied using this method. This method also offers a non-invasive way to determine biofilm formation on anodes of microbial fuel cells and preserves the anode for further studies.

Assessing Activity of Antimicrobial Agents and Screening Antibiotic-Resistant Bacteria Through DREAM Assay.

Antibiotics have assumed importance in the scene of medicine due to their activity against bacterial infections. During the course of evolution, bacteria have been developing routes to overcome damaging effects of antibiotics. Antibiotic resistance is an intriguing development that has taken the world of anti-microbial therapy by storm. Among the methods described in literature for assessing anti-microbial activity, those using metabolic activity as a measure of bacterial viability provide estimates closer to the actual. The dye reduction-based electron-transfer activity monitoring assay (DREAM assay) utilizes the redox dye methylene blue as an indicator of microbial activity. The DREAM assay coefficient is presented herein as a measure of the extent of microbial reduction of methylene blue to a colorless form under experimental conditions. This novel metric was successfully employed to evaluate activity of three common antibiotics-ampicillin, gentamicin, and ciprofloxacin-and leaf extracts of Azadirachta indica and Ocimum sanctum. Results corroborated significantly with the conventional disk diffusion method commonly used for anti-microbial testing. The principle of microbial electron transfer was then successfully extended to assess antibiotic susceptibility of known resistant and sensitive strains of Escherichia coli. This method possesses the advantage of detecting anti-microbial activity in a simple, cost-effective, and rapid manner.