Selenium stress in Ganoderma lucidum: A scanning electron microscopy appraisal

Physiological changes and gene responses during Ganoderma lucidum growth with selenium supplementation

Ganoderma lucidum basidiomycota is highly appreciated for its health and nutrition value. In the present study, Ganoderma lucidum was cultivated as selenium transformation carrier, and the physiological changes and gene responses by selenium supplementation were revealed through high-throughput RNA-Seq technology. As a result, selenium supplementation increased the stipe length and the cap size, but decreased the cap thickness of G. lucidum. Mineral salt supplementation could greatly promote the formation of triterpene acids and selenium in G. lucidum. The highest yield was gained in the treatment with selenium content of 200 µg/g. Subsequently, the tissues of G. lucidum at budding and mature stages in this treatment group were sampled for transcriptome analysis and compared to those of a control group without selenium supplementation. A total of 16,113 expressed genes were obtained from the transcriptome of G. lucidum, and GO-annotated unigenes were mainly involved in molecular functions and KEGG-annotated ones were highly expressed in ribosomal pathway. Furthermore, genes involved in carbon metabolism pathway were most promoted by selenium at budding stage of G. lucidum, while gene expression was the highest in the pathway of amino acid biosynthesis at mature stage of G. lucidum. Specially, selenium-related genes in G. lucidum, such as GL23172-G, GL29881-G and GL28298-G, played a regulatory role in oxidoreductase, antioxidant activity and tryptophan synthesis. The results provide a theoretical basis for further study of selenium-enriched mushrooms and aid to development of Se-enriched foodstuff and health products made from fungi.

Polymer Nanocomposites of Selenium Biofabricated Using Fungi

Nanoparticle-reinforced polymer-based materials effectively combine the functional properties of polymers and unique characteristic features of NPs. Biopolymers have attained great attention, with perspective multifunctional and high-performance nanocomposites exhibiting a low environmental impact with unique properties, being abundantly available, renewable, and eco-friendly. Nanocomposites of biopolymers are termed green biocomposites. Different biocomposites are reported with numerous inorganic nanofillers, which include selenium. Selenium is a micronutrient that can potentially be used in the prevention and treatment of diseases and has been extensively studied for its biological activity. SeNPs have attracted increasing attention due to their high bioavailability, low toxicity, and novel therapeutic properties. One of the best routes to take advantage of SeNPs' properties is by mixing these NPs with polymers to obtain nanocomposites with functionalities associated with the NPs together with the main characteristics of the polymer matrix. These nanocomposite materials have markedly improved properties achieved at low SeNP concentrations. Composites based on polysaccharides, including fungal beta-glucans, are bioactive, biocompatible, biodegradable, and have exhibited an innovative potential. Mushrooms meet certain obvious requirements for the green entity applied to the SeNP manufacturing. Fungal-matrixed selenium nanoparticles are a new promising biocomposite material. This review aims to give a summary of what is known by now about the mycosynthesized selenium polymeric nanocomposites with the impact on fungal-assisted manufactured ones, the mechanisms of the involved processes at the chemical reaction level, and problems and challenges posed in this area.

Alterations in Growth and Morphology of Ganoderma lucidum and Volvariella volvaceae in Response to Nanoparticle Supplementation

Use of nanoparticles (NPs) in several commercial products has led to emergence of novel contaminants of air, soil and water bodies. The NPs may exhibit greater ecotoxicity due to nano-scale dependent properties over their bulk counterparts. The present investigation explores the effect of in vitro supplementation of TiO₂, silica and silver NPs on radial growth and ultrastructural changes in the hyphae and spores of two mushroom genera, Ganoderma lucidum and Volvariella volvaceae. A concentration dependent decrease in radial growth on NP amended potato dextrose agar medium was recorded. However, in comparison to control, there was decrease in radial diameter on supplementation with TiO₂ NPs while an increase was recorded for silica and silver NPs amendments as compared to their bulk salts at same concentrations after 48 h of incubation. Optical microscopy studies showed decrease in the number of spores while increase in spore diameter and thinning of hyphal diameter on NPs supplementation. Scanning electron microscopy analysis of fungal growth showed presence of deflated and oblong spores in two fruiting strains of Ganoderma while Volvariella exhibited decreased sporulation. Further, hyphal thinning and branching was recorded in response to NP amendments in both the test mushrooms. Enhancement of protein content was observed on NP compared to bulk supplementation for all cultures, concentrations and hours of incubation except for TiO₂ NPs. Likewise, bulk and NP supplementations (at 100 mg L ^-1) resulted in enhanced laccase activity with occurrence of laccase specific protein bands on SDS-PAGE analysis.

Biosynthesis of selenoproteins by Saccharomyces cerevisiae and characterization of its antioxidant activities

The study investigated biosynthesis of selenoproteins by Saccharomyces. cerevisiae using inorganic selenium. Selenium supplement via two stages was carried out during fermentation and the physicochemical characteristics of selenoproteins and its antioxidant activities were examined through in vitro assessment procedures. After fermentation, dry cells weight (7.47 g/L) and selenium content (3079.60 μg/kg) in the yeast were achieved when fermentation time points at the 6th hour and the 9th hour were chosen to supplement 30% and 70% of 30 μg/mL Na₂SeO₃ respectively. A maximal yield of selenium content in selenoproteins reached 1013.07 μg/g under optimized culture conditions and was 133-fold higher than the control. One new band with molecular weight of 26.76 KDa appeared in conjugated selenoproteins of sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Surface structure of selenoproteins and the control was different by Scanning electron microscopy images. Infrared spectrometry analysis demonstrated that groups of HSe, SeO and C-Se-O involved in selenoproteins were important pieces of evidence showing presence of Se embedded in the protein molecule. Selenoproteins showed strong antioxidant activities on DPPH·, OH and ·O^2-, which was much higher than the control proteins. Therefore, the study provided an efficient selenium-enriched culture method of inorganic selenite to organic selenium and basis for selenoproteins applications.

Transcriptional profiling of Auricularia cornea in selenium accumulation

Auricularia cornea is a widely cultivated edible fungus with substantial nutritive value. This study aimed to enrich the multifunctional bionutrient element selenium in A. cornea to improve its quality and explore the accumulation of selenium in the fungus using high-throughput RNA-Seq technology. In general, the treatment group with a 100 µg/g supply of selenium outperformed the other treatment groups in terms of high yield, rich crude polysaccharides and a high total selenium concentration. Additional evidences demonstrated the budding and mature phases were two typical growth stages of A. cornea and were important for the accumulation of selenium. Therefore, the budding and mature phase tissues of A. cornea in the treatment group with a 100 µg/g supply of selenium were used for transcriptome analysis and compared to those of a control group that lacked additional selenium. A total of 2.56 × 105 unigenes from A. cornea transcriptome were assembled and annotated to five frequently used databases including NR, GO, KEGG, eggNOG and SwissProt. GO and KEGG pathway analysis revealed that genes involved in metabolic process and translation were up-expressed at the budding stage in response to selenium supplementation, including amino acid metabolism, lipid metabolism, ribosome. In addition, the differential gene expression patterns of A. cornea suggested that the up-expressed genes were more likely to be detected at the budding stage than at the mature stage. These results provide insights into the transcriptional response of A. cornea to selenium accumulation.