Characterizing fungal communities in medicinal and edible Cassiae Semen using high-throughput sequencing

Cassiae Semen (CS) has been widely used as roasted tea and traditional Chinese medicine for decades. However, CS is easily contaminated by fungi and mycotoxins during pre-harvest and post-harvest process, thus posing a potential threat to consumer health. In this study, we used the Illumina MiSeq PE300 platform and targeted the internal transcribed spacer 2 sequences to survey the occurrence of fungi in raw and roasted CS samples. Results showed the fungal contamination in all 12 test samples. Ascomycota was the prevailing fungus at the phylum level, with the relative abundance of 66.50%-99.42%. At the genus level, Aspergillus, Cladosporium, and Penicillium were the most dominant genera, accounting for 0.66%-85.51%, 0.20%-29.11%, and 0.11%-32.92% of the fungal reads, respectively. A total of 68 species were identified, among which six potential toxigenic fungi belonging to Aspergillus, Penicillium, Candida, and Schizophyllum genera were detected. Moreover, differences in fungal communities were observed in raw and roasted CS samples. In conclusion, amplicon sequencing is feasible for analyzing fungal communities in CS samples, which provides a new approach to investigate the fungal contamination in edible-medicinal herb, thereby ensuring food safety and drug efficacy.