Biological routes have been extensively explored in the synthesis of metallic nanoparticles due to their simplicity and low cost. Among metallic nanoparticles, silver nanoparticles (AgNPs) are widely used in medical applications because of their potent antimicrobial activity. In this work, the ability of the mycelium-free fungus extract produced by Chilean white-root Stereum hirsutum and two plant extracts (green tea and dill) were used in the synthesis of AgNPs. The synthesized nanoparticles were extensively characterized by different techniques. The antibacterial activity of the nanoparticles was demonstrated against the Gram-positive strain Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 3229 (standard CLSI); and the Gram-negative bacterial strains (standard CLSI) Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13803 and the multidrug-resistant Pseudomonas aeruginosa KPC 37. The values of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were obtained in the range of 1.56–25 µg mL−1. AgNPs synthesized by dill extract showed lower values of MIC and MBC, compared to other nanoparticles. The potent antibiofilm ability of AgNPs was demonstrated, including against the multidrug-resistant P. aeruginosa KPC 37 strain. All synthesized nanoparticles demonstrated antibiofilm activity. AgNPs synthesized by fungus extract demonstrated superior antibiofilm activity, compared to AgNPs synthesized by green tea or dill, at low concentration (1.56 µg mL−1). To our best knowledge, this is the first report to compare the antioxidant and antibacterial effects of AgNPs synthesized by different biological entities (green tea, dill and S. hirsutum) with great importance in the combat of resistant bacteria and biofilms.
The excessive utilization of fossil fuels consequently causes global climate change because of the emission of greenhouse pollutants. Hence, hydrogen is considered as the major energy carrier in the future because of its high conversion capability, recyclability and non-polluting nature. The present study focuses on the enhancement of fermentative biohydrogen production from high-organic-rich distillery spent wash under mesophilic conditions with optimization of substrate concentrations. The experimental results depict that 60 g/L substrate concentration was favorable for biohydrogen production with a biohydrogen yield of 0.6 L/L. Pretreatment of the substrate was one of the another specific objectives which was carried out through electrocoagulation using iron (Fe) (−)/Fe (+). The electrocoagulation showed the maximum biohydrogen yield of 1.4 L/L at 15-min reaction time under favorable substrate concentrations.
A new form of coin-operated or electronic card-operated water vending machine; popularly known as the water ATMs (Automated Teller Machine) are gaining popularity as a ‘smart’ yet a ‘low-cost’ technology to provide safe water at nominal rates in India. Water ATMs are being currently experimented as a market-based solution on the idea of social entrepreneurship to provide safe drinking water to the urban poor in Delhi who are inadequately served by the public utility network. Based on a primary survey, the present case study aims to look at the challenges and opportunities these water ATMs pose. The study assesses its scope for further expansion as a solution to water security for urban poor residing in low income areas by analysing the issues of both supply side as well as demand side management of this technology. It is believed that water ATMs have tremendous potential to reduce waterborne diseases affecting the lives of millions of people in India and can minimize plastic waste and prevent plastic contamination as posed by the booming packaged water industries. Though water tariffs are nominal, water ATMs, for the first time are operating on the model of a paid community standpipe, in urban poor areas in India. So the big question remains whether the water ATMs can be seen as a complimentary source of safe water to the urban poor or it can be turned into an alternative option for universal coverage of piped network.
Wild-type (WT) and DCMU-tolerant mutant strain of microalga Scenedesmus vacuolatus were used to study the effect of different spectral quality of light on the growth and biochemical constituents. Results showed that overall growth, cell constituents and total organic carbon were higher in the mutant strain than the WT under all types of light irradiances. However, green and orange light conditions were found to be optimum for both WT and mutant strain, respectively. FTIR analysis of biomass of WT and the mutant strain showed the minor difference in the lipid/carbohydrate (0.82 ± 0.061, 0.71 ± 0.05, respectively) and lipid/protein (0.52 ± 0.026, 0.59 ± 0.040, respectively) ratios due to changes in the spectral quality of light. Flow cytometer analysis of WT and mutant cells, grown under green and orange light, respectively, exhibited maximum lipid content, but the lipid content in the mutant strain was higher than the WT. The PAM fluorimeter parameters ΔF/F m′, F v/F o ABS/RC, RC/ABS and ET0/RC derived from chlorophyll fluorescence induction (OJIP) curve of WT and the mutant strain showed better photosynthetic performance (RC/ABS) in the green light-grown WT and orange light-grown mutant strain. However, a reduced level of growth, cell constituents and photosynthetic yield in the WT than the mutant strain might be attributable to the higher value of NPQ, indicating greater loss of absorbed photo-energy in the WT cells. Thus, efficient utilization of spectral quality of light irradiance by the microalga was strain-specific, depending upon the photosynthetic attributes of individual strain as evident from the comparison of photosynthetic properties of both wild-type and DCMU-tolerant mutant strain.
The future of many tree species is at risk due to the rapid decline of the world’s forests, over-exploitation for timber, seeds, oils, resins, fruits and bark. In addition, seed germination in many threatened species is convoluted due to various physical factors such as moisture, light and the presence of thick seed coat as well as physiological factors such as seed dormancy. Studies pertaining to seed germination, storage behaviour, dormancy-breaking techniques, particularly of threatened tree species at global level are limited. Therefore, the present study was conducted to assess the progress made in the field of seed germination as well as the challenges that exist in the regeneration of such species that are of conservation value. The results obtained from the analysis of 78 threatened tree species showed that moisture is a critical factor for recalcitrant seeds, while species with orthodox seeds require a pre-treatment for breaking dormancy. Although most of the studies on dormancy-breaking techniques have demonstrated the effectiveness of one or two methods on seed germination, a combination of treatments as well as use of plant growth regulators improved the ability of seeds to germinate. Water, light, nutrients and a favourable substratum are major regulatory factors that affect germination, growth and establishment of tree species. The findings emphasize the need to develop guidelines for proper seed handling and understand germination protocols necessary for ecosystem management that would aid both in maintaining biodiversity values and conservation of threatened species.