Since common physicochemical factors control the cellular location of SeNPs, both the intracellular and extracellular locations of mycosynthesized SeNPs were observed by many researchers
[214][212][215][33,262,264]. Thus, filamentous fungi
Aureobasidium pullulans,
Mortierella humilis,
Trichoderma harzianum, and
Phoma glomerata were capable of intra- and extracellular bioproduction of SeNPs
[214][33]. The red deposit was confirmed as elemental selenium during fungal growth on Se-containing media. Along with Se
0 formation, selenium oxide was found in the case of
Trichoderma harzianum culture with 1 mM selenite. Both particle sizes and SeNPs concentrations were determined by the SP-ICP-MS technique. Only
A. pullulans and
M. humilis produced SeNPs in 10-day culture, with diameters ca. 60 and 48 nm, respectively. In 20- and 30-day cultures, particles were enlarged in diameter to reach about 78 and 61 nm. Using the SP-ICP-MS method, only a low SeNP level was detected in
T. harzianum and
P. glomerata supernatants of liquid cultures
[214][33]. Rosenfeld et al. showed that the ascomycete fungi (
Pyrenochaeta sp.,
Acremonium strictum,
Plectosphaerella cucumerina,
Stagonospora sp.,
Alternaria alternata,
Paraconiothyrium sporulosum) produced Se
0 by Se inorganic salts reduction, with the NPs being strongly bound by the fungal biomass for all six species used
[215][264]. SeNPs’ diameter ranged from 50–100 nm (
Alternaria alternata) to 200–300 nm (other fungal species). Particles were spherical. Results of XRD analysis demonstrated that the diffraction patterns of all SeNPs were X-ray amorphous, although two of the analyzed extracellular SeNPs mycosynthesized by
Acremonium strictum were crystalline with a d-spacing of 0.37 nm. Residual dissolved Se(IV) and Se(VI) concentration values were determined by conductivity measurements using an ion chromatography system enabling a simultaneous quantification of both oxyanions, comprising Se(IV) and Se(VI), with a detection limit of micromole/L for each anion. Analysis for total selenium associated with fungal biomass was performed using the inductively coupled plasma optical emission spectroscopy (ICP-OES). The presence of Se
0 was confirmed by SEM EDS. Transmission electron microscopy revealed intracellular and extracellular SeNPs in all fungal species used
[215][264]. Biosynthesis of SeNPs by
Mariannaea sp. HJ was reported for the first time very recently
[212][262]. Various culture conditions were studied, including SeO
2 concentrations and pH of reaction media. To characterize the resultant SeNPs, the multimethod approach was used: UV-Vis, TEM, SEM, XRD, FTIR, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used. TEM images depicted the SeNPs’ deposition both on the fungal cell wall and in the cytoplasmic region, thus suggesting the biotransformation of Se(IV) into elemental selenium to occur in extracellular and intacellular locations, which could provide a template for these bioreduction processes
[212][262].