Stimulatory effects of Ultraviolet-B irradiation on bioactives, phenolics, beta-glucans, vitamin D2 and antioxidant activities in submerged fermented Pleurotus eryngii mycelia

Abstract

This study explores how ultraviolet-B (UV-B) light can boost the nutritional and medicinal benefits of Pleurotus eryngii mycelia. By exposing freeze-dried P. eryngii mycelia to UVB light for various durations (0–60 min), a significant rise in vitamin D2 levels was observed, peaking at 314.75 μg/g after 40 min. Total phenols increased from 12.52 to 17.54 mg GAE/g, flavonoids from 1.19 to 1.72 mg QE/g, and beta-glucans from 26.18 % to 32.21 %, along with notable improvements in antioxidant activities. UVB exposure also enhanced the amino acid profile, with substantial boosts in essential amino acids like glutamic acid, arginine, and threonine. Significant changes were observed when comparing the metabolite profiles of control and UV-treated P. eryngii mycelia. Some key compounds, like Isosorbide Dinitrate, increased from 1.56 % to 3.24 %, while n-hexadecanoic acid rose from 19.91 % to 27.73 %, and octadecanoic acid jumped from 0.36 % to 1.09 %. These changes suggest enhanced antioxidant and anti-inflammatory properties. Other compounds, such as phenol, 3,5-bis(1,1-dimethylethyl)-, eicosane, Pyrrolo [1,2-a]pyrazine-1,4-dione, and ergosta-5,7,9 (11),22-tetraen-3-ol, also significantly increased, indicating enhanced health benefits and potential anti-cancer properties. Analyses using FTIR spectroscopy and SEM revealed molecular and structural changes due to UVB treatment, and GC-MS confirmed the presence of significant medicinal bioactives. These findings suggest that UVB irradiation can significantly enhance the health-promoting qualities of P. eryngii mycelia, making them even more beneficial as functional foods and nutraceuticals.