Antioxidant Activities of Exopolysaccharides Extracts from Two Endemic Fungi from Patagonia.

A great number of free radicals have a negative impact on the human body, and an increased interest in the identification of new natural molecules with antioxidant properties has emerged due to concerns about synthetic antioxidants. Here, the antioxidant effect of four exo-polysaccharides (EPS) extracts obtained from submerged cultivation of Nothophellinus andinopatagonicus and Pseudoinonotus crustosus (N and P, respectively) in two culture media (M1 and M2) at 2 concentrations (100 and 250 µg/ml) was studied; then, its relation with the chemical composition of the EPS was evaluated. To assess the antioxidant activities of the extracts, several in vitro assays were performed: DPPH and ABTS radical scavenging, ferric-reducing antioxidant power, chelating ability on ferrous ions, and inhibition of the lipid peroxidation. The concentrations tested here were much lower than those reported in previous works. Despite variations in chemical composition and monosaccharide profiles among the extracts, all demonstrated antioxidant activity, although the type of activity differed; only P-M1 exhibited a good antioxidant activity across all assays. This extract contained the highest proportion of phenolic compounds, and also displayed the highest radical scavenging activity. Although the utilization of polysaccharides as functional food ingredients remains limited, we propose P-M1 as a promising candidate for a nutraceutical product. Additionally, a formulation could be made with a combination of extracts to create an antioxidant-rich supplement. Additional research is needed to confirm our findings in a cellular environment and to elucidate the mechanisms that drive their antioxidant activities, ultimately facilitating their development and utilization as nutraceutical products.

Exiguobacterium sp. as a bioinoculant for plant-growth promotion and Selenium biofortification strategies in horticultural plants.

Plant growth-promoting rhizobacteria (PGPR) have a positive effect on plant development and being a promising way to enhance crop productivity and as substitution of chemical fertilizers. Selenium (Se) is an important trace element and its intake is usually lower than the daily minimum amount required for humans; hence, there is a demand on the design of Se biofortification strategies. Here, the genetic traits known to be associated with Plant-Growth Promotion (PGP) and Se biotransformation of Exiguobacterium sp. S17 were evaluated through genome analysis. Its growth-promoting capacity was tested through plant-growth promotion assays in laboratory and field conditions, using Brassica juncea (indian mustard), Beta vulgaris (chard), and Lactuca sativa (lettuce). Additionally, the Se biotransformation ability of Exiguobacterium sp. S17 was evaluated and the obtained selenized bacteria were tested in mustard plants. The sequenced bacteria genome revealed the presence of multiple genes involved in important functions regarding soil and plant colonization, PGP and Se biotransformation. Moreover, it was demonstrated that Exiguobacterium sp. S17 enhanced plant growth and could be useful to produce Se accumulation and biofortification in accumulator plants such as mustard. Thereby, Exiguobacterium sp. S17 might be used for developing new, sustainable, and environmentally friendly agro-technological strategies.

Biogenic selenium nanoparticles with antifungal activity against the wood-rotting fungus Oligoporus pelliculosus.

Selenium nanoparticles (SeNPs) have antimicrobial and antifungal activity. SeNPs using Se resistant bacteria is a low cost and eco-friendly technology. Fungal contamination of wood during drying is one of the main causes of economic losses in the wood industry. The bacterium Delftia sp. 5 resistance to Se and its ability to produce SeNPs able to inhibit the growth of the wood brown-rotting fungus Oligoporus pelliculosus was analyzed. The strain showed an optimal SeNPs production when selenite concentration was 160 mg L -1. The SeNPs were spherical with an average size 192.33 ± 8.6 nm and a zeta potential of -41.4 ± 1.3 nm. The SeNPs produced by Delftia sp. 5 (33.6 ± 0.1 mg L -1 Se) inhibited the growth of O. pelliculosus in agar plates and in Nothofagus pumilio (Lenga) wood samples. Delftia sp. 5 SeNPs could be used for embedding lenga wood prior to drying for preventing the growth of the deteriorating fungi O. pelliculosus.