Stereum hirsutum

2.1. LC-MS profiling of S. hirsutum FP-91666 under different fermentation conditions Microorganisms are susceptible to culture conditions, such as medium constituents, temperature, medium status, and so on. Altering these factors can lead to changes in the chemical diversity of specialised metabolites. In this study, S. hirsutum FP-91666 was grown in five types of media (CMB, GPY, PDB, WG, and YMG) together with their solid condition (CMA, GPYA, PDA, WGA, and YMGA), and then LC-MS analyses of the extracts were used to reveal the metabolite diversity of S. hirsutum FP-91666 and obtain as many undescribed metabolites as possible. The total ion chromatogram (TIC) profiles of the extracts are almost the same for the five solid media (Fig. 1A), and the retention times show that these metabolites are mainly non- or low polar metabolites. However, the TIC profiles of the liquid cultural extracts (Fig. 1B) show that the metabolites from the WG extract are more abundant, and the retention times of the metabolites reveal that the metabolites are mainly medium or highly polar compounds. In order to further understand the metabolites in the extract chromatograms, we selected ion monitoring mode (SIM) to analyze the LC-MS chromatograms. The products of the strain cultivated on WGB medium were more diverse and abundant than those of strains grown on the other culture media (Fig. 1C). According to the SIM profiles, some highly enriched ESIMS peaks were found in LC-MS chromatograms of extracts from S. hirsutum FP-91666 on WGA medium, such as sterostrein Q m/z 244 [M + H] +, stereumamide D m/z 431 [M + H] +, and stereumamides B and H m/z 358 [M + H] +. Several unknown peaks were also present in the product spectra of the extracts. A positive SIM peak at m/z 392 was present in the product spectra (Fig. 1C) of the strain cultured on the WGB medium and the relative strength of the peak was strong (NL: 2.16E 8). Other positive SIM peaks at m/z 374 and 290 (Fig. 1C) were also observed in the LC-MS profiles. Based on these results, the WGB medium was selected for the fermentation of S. hirsutum FP-91666 to explore undescribed metabolites.Published as part of Pu, Xue-Juan, Hu, Qian-Yi, Li, Su-Su, Li, Guo-Hong & Zhao, Pei-Ji, 2021, Sesquiterpenoids and their quaternary ammonium hybrids from the mycelium of mushroom Stereum hirsutum by medium optimization, pp. 1-8 in Phytochemistry (112852) (112852) 189 on page 3, DOI: 10.1016/j.phytochem.2021.112852, http://zenodo.org/record/825926