Screening, Isolation and Identification of High Antioxidant Strains from 16 Kinds of Mushrooms

Aims: To promote the rational exploration of the mushroom resources, this study evaluated the in vitro antioxidant activity of 16 kinds of mushrooms collected from the Sichuan province in China and completed the identification of the optimal active strains. Place and Duration of Study: School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan province, China. April 2019 to May 2020 (13 Months). Methodology: 16 kinds of mushrooms were collected in the wild. These strains were isolated and cultivated. The extract’s antioxidant activities of fermentation broth and mycelium were assessed using the DPPH radical-scavenging method. The higher activity strains were also evaluated by Trolox equivalent antioxidant capacity (TEAC) and the Ferric reducing antioxidant power (FRAP) assay. Meanwhile, the contents of total flavonoids and total phenols were determined. Finally, The highly active strains were identified by internal transcribed spacer (ITS) Identification. Results: All extract of fermentation broth and mycelium from 16 kinds of mushrooms had scavenging effects on DPPH. Among them, strain No. 6 and No. 7 exhibited obvious antioxidant capacity, and the scavenging rates of their fermentation broths on DPPH were 89.47% and 84.27%, respectively. And the results of TEAC and FRAP were consistent with those of DPPH. Besides, these two kinds of mushrooms were all rich in phenolic and flavonoid compounds, and the content in the fermentation broth was significantly higher than that in the mycelium, indicating that phenolic and flavonoid substances may be the material basis of their antioxidant effect. The strain No. 6 and No. 7 were confirmed to be Bjerkandera and Nigrospora sp, respectively by 16S nrDNA sequence identification. Conclusion: The results showed that Bjerkandera and Nigrospora sp. possessed the highest antioxidant capacities with rich total phenolic and total flavonoids. They could be potential sources of natural antioxidants for further exploration and application.