Use of silver and silver salts is as old as human civilization but the fabrication of silver nanoparticles (Ag NPs) has only recently been recognized. They have been specifically used in agriculture and medicine as antibacterial, antifungal and antioxidants. It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus Candida albicans by binding Ag/Ag+ with the biomolecules present in the microbial cells. It has been suggested that Ag NPs produce reactive oxygen species and free radicals which cause apoptosis leading to cell death preventing their replication. Since Ag NPs are smaller than the microorganisms, they diffuse into cell and rupture the cell wall which has been shown from SEM and TEM images of the suspension containing nanoparticles and pathogens. It has also been shown that smaller nanoparticles are more toxic than the bigger ones. Ag NPs are also used in packaging to prevent damage of food products by pathogens. The toxicity of Ag NPs is dependent on the size, concentration, pH of the medium and exposure time to pathogens.

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A review on biosynthesis of silver nanoparticles and their biocidal properties.

The use of fungi as reducing and stabilizing agents in the biogenic synthesis of silver nanoparticles is attractive due to the production of large quantities of proteins, high yields, easy handling, and low toxicity of the residues. Furthermore, this synthesis process coats the nanoparticles with biomolecules derived from the fungus, which can improve stability and may confer biological activity. The aim of this review is to describe studies in which silver nanoparticles were synthesized using fungi as reducing agents, discussing the mechanisms and optimization of the synthesis, as well as the applications. The literature shows that various species of fungus have potential for use in biogenic synthesis, enabling the production of nanoparticles with different characteristics, considering aspects such as their size, surface charge, and morphology. The synthesis mechanisms have not yet been fully elucidated, although it is believed that fungal biomolecules are mainly responsible for the process. The synthesis can be optimized by adjusting parameters such as temperature, pH, silver precursor concentration, biomass amount, and fungus cultivation time. Silver nanoparticles synthesized using fungi enable the control of pathogens, with low toxicity and good biocompatibility. These findings open perspectives for future investigations concerning the use of these nanoparticles as antimicrobials in the areas of health and agriculture.

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Synthesis of Silver Nanoparticles Mediated by Fungi: A Review.

Composting is the controlled conversion of degradable organic products and wastes into stable products with the aid of microorganisms. Composting is a long-used technology, though it has some shortcomings that have reduced its extensive usage and efficiency. The shortcomings include pathogen detection, low nutrient status, long duration of composting, long mineralization duration, and odor production. These challenges have publicized the use of chemical fertilizers produced through the Haber–Bosch process as an alternative to compost over time. Chemical fertilizers make nutrients readily available to plants, but their disadvantages outweigh their advantages. For example, chemical fertilizers contribute to greenhouse effects, environmental pollution, death of soil organisms and marine inhabitants, ozone layer depletion, and human diseases. These have resulted in farmers reverting to the application of composts as a means of restoring soil fertility. Composting is a fundamental process in agriculture and helps in the recycling of farm wastes. The long duration of composting is a challenge; this is due to the presence of materials that take a longer time to compost, especially during co-composting. This review discusses the proper management of wastes through composting, different composting methods, the factors affecting composting, long-duration composting, the mechanism behind it, the present trends in composting and prospects. The extraction of mono-fertilizers from compost, development of strips to test for the availability of heavy metals and pathogens as well as an odor-trapping technique can go a long way in enhancing composting techniques. The addition of activators to raw materials can help to improve the nutritional quality of compost. This review further recommends that degradable organic material in which composts slowly should be assessed for their ability to mineralize slowly, which could make them advantageous to perennial or biennial crops. Viricides, fungicides, anti-nematodes, and anti-bacterial of plant or organic sources could as well be added to improve compost quality. The enhancement of composting duration will also be useful.

Waste Management through Composting: Challenges and Potentials

Factors affecting mushroom Pleurotus spp.

Silver nanoparticles: An integrated view of green synthesis methods, transformation in the environment, and toxicity.

This study is the first report on the usage of fresh fruiting bodies of Enoki mushroom (Flammulina velutipes) as a new green reducer agent incorporated in the mycosynthesis of gold nanoparticles. The mycosynthesized AuNP was characterized for its physical and chemical properties using optical observation, UV–vis spectrometer, FESEM, AFM, DLS, XRD, Zeta Potential, and FTIR analyses. The optimized AuNPs were then tested for its efficacy in the decolorization of Methylene Blue (MB). The purple color of AuNPs indicates that the solution contains a mixture of triangular, spherical, and irregular shapes with an average of size 74.32 nm. The pattern of XRD clearly showed that the formed AuNPs were crystalline while DLS and Zeta Potential data showed that mycosynthesized AuNPs exhibited good stability and aggregation properties in colloidal form. FTIR showed the attachments of polysaccharides, amino acids and phenol as reducer agents on AuNPs. The efficacy test exhibited that the degradation of MB increased with the increase of the incubation time in presence of AuNPs. The proof-of-concept that mycosynthesized AuNPs by fungal natural organic materials of Flammulina velutipes can act as catalysts in reducing the MB dye is proven by the best decolorization of MB at 75.35 % after 4 h soak.

Mycosynthesis of gold nanoparticles using the extract of Flammulina velutipes, Physalacriaceae, and their efficacy for decolorization of methylene blue

Abstract This review distinguishes myco-nanotechnology using metallic nanoparticles (meta-NPs) synthesized from edible mushroom matter. Green chemistry approaches were attempted to myco-synthesize meta-NPs (viz., Ag-NP, Au-NP, Se-NP, CdS-NP, Fe-NP, Pa-NP, and ZnS-NP) via different routes using edible mushrooms and have been tested toward 79% biomedical and 21% industrial applications. Biomaterials were used as biofactors to form metallic NPs. In mushroom science, mycomaterials of mushrooms were used at different percentages to mycosynthesize in an ecofriendly/green way; mycomaterials such as crude extracts of basidocarp (53%), mycelial extract or free cell filtrate (28%), in crude form or in purified form such as polysaccharides at different percentages; 9% (especially glucan), proteins/enzymes (7%) and polysaccharides protein complex (3%) as new research lines. Generally, in this field of mushroom nanoparticles about 84% of mycosynthesized NPs using mushrooms are placed outside the fungal cell (extracellular) and 16% are intracellular in the mushroom hyphae. The knowledge of the performance and influence of meta-NPs in edible mushrooms has developed in the last 10 years. Generally, while Agaricus bisporus was the first to be used in agricultural production Pleurotus spp. has the highest use (38%) in the formation of mushroom NPs. Furthermore, silver nanoparticles (Ag-NPs) have been biosynthesized more often in the fungi kingdom; also, Ag-NPs made up the largest part (64%) in the formation of nanoparticles in mushroom science. Mushroom meta-NPs usually have a spherical shape with sizes from 0.4 nm up to ≤300 nm but most of them are <75 nm. A few recent applications have affected the inhibition of the growth of human pathogenic bacteria by mushroom Ag-NPs in combination with antibiotics. Myco-synthesized meta-NPs using mushrooms, especially Ag-NPs, Au-NPs and Se-NPs, are potent against various cancer cell lines. Thus, these NPs can be used in numerous pharmaceutical drugs. Also, the transport of pharmaceutical drugs and biomaterials using NPs of edible mushrooms is considered a very undervalued and new application in the drug and gene fields. Mushroom meta-NPs were investigated for industrial applications such as inorganic NPs, carbon nanotubes and the treatment of waste as nano-biosorbents for the adsorption of toxic metals for cleaning the environment using eco-friendly natural materials for reducing the pollution of the environment in the future.

Mycosynthesis of nanoparticles using edible and medicinal mushrooms

Mycosynthesis of silver nanoparticles by Pleurotus cornucopiae var. citrinopileatus and its inhibitory effects against Candida sp.

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The nutritional and medical benefits of agaricus bisporus : a review

This work aims to find a new green reducer agent for synthesis gold nanoparticles (AuNPs). Fresh fruiting bodies of shiitake mushroom (Lentinula edodes) were used to mycosynthesize AuNPs, which were characterized using change in color, UV–vis, FE-SEM, AFM, Zetasizer, Zeta Potential, XRD, EDX, and FTIR analyses. The purple color is a sign of biosynthesizing AuNPs. The UV–vis spectrum showed an absorption peak at 568 nm due to incitation of Surface Plasmon Resonance in AuNPs colloidal solution. FE-SEM images exhibited that most of the AuNPs have triangular, hexagonal, spherical and irregular shapes with an average of sizes reached 72 nm. The XRD pattern clearly explained that AuNPs formed in this work were crystalline. The EDX proved that the nanoparticles are AuNPs. FTIR exhibited the role of amino acids, polysaccharides and phenols as reducer agents. The value of zeta potential indicates good quality with the aggregation of particles.

Mustafa Nadhim Owaid

Papers

Mycosynthesis of gold nanoparticles using the extract of Flammulina velutipes, Physalacriaceae, and their efficacy for decolorization of methylene blue

Mycosynthesis of nanoparticles using edible and medicinal mushrooms

Mycosynthesis of silver nanoparticles by Pleurotus cornucopiae var. citrinopileatus and its inhibitory effects against Candida sp.

The nutritional and medical benefits of agaricus bisporus : a review

Mushroom-assisted synthesis of triangle gold nanoparticles using the aqueous extract of fresh Lentinula edodes (shiitake), Omphalotaceae