Selenium Uptake by Edible Oyster Mushrooms (Pleurotus sp.) from Selenium-Hyperaccumulated Wheat Straw

Rare earth contamination of edible vegetation: Ce, La, and summed REE in fungi

The increasing and diversified use of rare earth elements (REE) is considered a potential source of pollution of environmental media including soils. This work documents critically overview data on the occurrence of REE in the fruiting bodies of wild and farmed species of edible and medicinal mushrooms, as this was identified as the largest published dataset of REE occurrence in foodstuff. Most of the literature reported occurrences of cerium (Ce) and lanthanum (La), but a number of studies lacked data on all lanthanides. The Ce, La, and summed REE occurrences were assessed through the criteria of environmental geochemistry, analytical chemistry, food toxicology, mushroom systematics, and ecology. Ce and La accumulate similarly in fruiting bodies and are not fractionated during uptake, maintaining the occurrence patterns of their growing substrates. Similarly, there is no credible evidence of variable REE uptake because the evaluated species data show natural, unfractionated patterns in accordance with the Oddo-Harkins' order of environmental lanthanide occurrence. Thus, lithosphere occurrence patterns of Ce and La as the first and the third most abundant lanthanides are reflected in wild and farmed mushrooms regardless of substrate and show that Ce is around twice more abundant than La. The current state of knowledge provides no evidence that mushroom consumption at these REE occurrence levels poses a health risk either by themselves or when included with other dietary exposure. Macromycetes appear to bio-exclude lanthanides because independently reported bioconcentration factors for different species and collection sites, typically range from < 1 to 0.001. This is reflected in fruiting body concentrations which are four to two orders of magnitude lower than growing substrates. KEY POINTS: •Original REE occurrence patterns in soils/substrates are reflected in mushrooms •No evidence for the fractionation of REE during uptake by fungi •Mushrooms bio-exclude REE in fruiting bodies.

Influence of selenium on the mycelia of the shaggy bracket fungus, Inonotus hispidus

BACKGROUND

Selenium (Se) is a needed trace element for animals and humans. Many fungi have effective mechanisms to acquire, transform and accumulate Se in organic form. In this study, the effects of inorganic Se (sodium selenite) on the medicinal fungus Inonotus hispidus was investigated.

RESULTS

Inonotus hispidus was capable of tolerating up to 3.85 mmol L^-1 selenite, at which ~85% growth inhibition was seen, with 50% growth inhibition occurring at ~1 mmol L^-1 selenite. Growth in 0.29 mmol L^-1 Se resulted in I. hispidus mycelium with 115 times higher Se levels compared to growth in standard media, and an organic Se content of 86% to total Se content. The influence of Se accumulation on morphological features of I. hispidus were examined by microscopic and scanning electron microscopic observation. These data revealed significant shrinkage and deformations of I. hispidus hyphae with decreased branching and collapse of clamp connections under higher Se stress. However, conidial production in I. hispidus increased dramatically. The influence of Se on mycelial growth could be recovered by reinoculation in standard media. Se accumulation had only minimal impacts on the yield of the potential selenocompounds such as amino acids, proteins and polysaccharides. By contrast, Se-enriched I. hispidus mycelium was of higher quality due to reduction in crude fat and total ash contents.

CONCLUSIONS

These data provide basic and applied information on the feasibility of producing selenized I. hispidus as an enriched and better quality product. © 2021 Society of Chemical Industry.

Effect of drying, blanching, pickling and maceration on the fate of 40K, total K and 137Cs in bolete mushrooms and dietary intake

The effects of blanching, blanching and pickling and maceration on the leaching of ¹³⁷Cs and ⁴⁰K from the flesh of three edible bolete mushroom species-Boletus edulis, Leccinum scabrum and Leccinum versipelle-were investigated. Significant (p < 0.05) decreases in activity were observed but varied depending on the treatment. Relative to fresh mushrooms, blanching decreased the activity concentration of ¹³⁷Cs by 15 ± 13%, and of ⁴⁰K, by 16 ± 7%, but blanching and pickling (vinegar) reduced activity more effectively, by 55 ± 8% and 40 ± 20% respectively. The corresponding losses of ¹³⁷Cs and ⁴⁰K through maceration of dried, powdered mushrooms were 38 ± 11% and 35 ± 14% ww, respectively. These results indicate that traditional domestic processing methods may not be as efficient at excluding ¹³⁷Cs radioactivity as shown in some other studies. The activity concentration of ¹³⁷Cs in a typically sized (100 g) portion of a processed mushroom (sourced from nearshore regions of the southern Baltic Sea coast near Gdańsk in 2015) meal was projected to be low, i.e. in the range of 0.51 to 12 Bq kg^-1 ww. The corresponding effective dose of ¹³⁷Cs from blanched, blanched and pickled and macerated mushrooms per capita was also assessed to be low, from 0.001 to 0.010 μSv. Nutritionally, the median concentration of potassium (330 mg) in 100 g portions of blanched or pickled mushrooms would account for around 7% of the adequate adult daily intake.

Mycochemical Changes Induced by Selenium Enrichment in P. ostreatus Fruiting Bodies

The effects of selenium enrichment on the biological efficiency, phenolic compounds, amino acid profile, antioxidant capacity, and cellular antioxidant activity (CAA) were evaluated in Pleurotus ostreatus fruiting bodies (FB) harvested during three sequential flushes. Sodium selenate was used to reach selenium content of 17.5 or 5.8 mg/kg in the sorghum straw substrate. Biological efficiency and total selenium content increased. One of the main differences among treatments was in ergothioneine content, an indicator of oxidative stress that was positively related with valine and isoleucine contents and negatively related to leucine and phenylalanine. Besides ergothioneine, nucleosides derived from adenine and uracyl were the major peaks observed in all treatments, and coumaric and ferulic acids were found in the bound phenolics extract. Selenium enrichment also affected the antioxidant capacity, and particularly the methanolic extract obtained from the second flush of FB cultivated in selenium-enriched substrate (17.5 mg/kg) had the best CAA.