Sanghuang is a lethal or pathogenic fungus that damages a variety of hardwood species, causing living wood to decay and form large fruiting bodies (Kim, Hohenlohe, Kim, Seo, & Klopfenstein, 2016). However, the economic value of this pathogenic fungus outweighs the damage it causes. The fruiting bodies formed by Sanghuangporus spp. are well-known mushrooms that have been used as traditional medicine for thousands of years in China and other East Asian regions (Han et al., 2016). The most ancient record of sanghuang that is currently available is the “Shen Nong Materia Medica”, which was written around 102–200 A.D. Although this record was written before the advent of modern science, it was empirically found that Sanghuangporus spp. were indeed effective against diseases. In recent decades, Sanghuangporus has received widespread attention for its anti-inflammatory and anti-cancer effects (Lin, Deng, Huang, Lin, et al., 2017; Lin, Deng, Huang, Wu, Chen, et al., 2017; Lin, Deng, Huang, Wu, Lin, et al., 2017; K. Liu, Xiao, Wang, Chen, & Hu, 2017; M. M. Liu, Zeng, Li, & Shi, 2016; Xue, Sun, Zhao, Zhang, & Lai, 2011), which are due to a variety of bioactive substances produced by Sanghuangporus spp., such as polysaccharides (Q. Ge, Mao, Zhang, Wang, & Sun, 2013), flavonoids (Y. R. Ge et al., 2012), triterpenoids (Cai et al., 2019), and polyphenols (Zhang et al., 2019).
Currently, three species of Sanghuangporus have been proved to have medicinal properties, namely S. baumii, S. vaninii, and S. sanghuang (M. D. Wu et al., 2019; S. H. Wu et al., 2012; Zhou, Ghobad-Nejhad, Tian, Wang, & Wu, 2020). The taxonomy of Sanghuangporus has been a constant topic of debate due to the high levels of phenotypic plasticity. In fact, it wasn't until 2016 that the Sanghuangporus was identified as a new genus, rather than a clade of Inonotus. Sanghuangporus sanghuang was identified and named by Wu et al. (S. H. Wu et al., 2012) and is considered to be the only true sanghuang. Sanghuangporus vaninii can produce fruiting bodies under artificial conditions, so it is widely sold in medicinal markets (Zhou et al., 2020). Sanghuangporus baumii parasitic on the trunk of Syringa reticulata and cannot be cultivated under artificial conditions. It also contains bioactive substances with anti-tumor and immunomodulation activity, but it is not as well-known as S. sanghuang and S. vaninii. The failure of cultivation greatly restricted the research and the industrialization of S. baumii. This failure is most likely due to a lack of knowledge of appropriate cultivation conditions and fruiting management. To date, it remains unknown how the medium, pH, and temperature affect the mycelial growth of S. baumii, and there have been very few reports on fruiting body cultivation and management.
Compared with fruiting bodies, mycelia also contain a large number of bioactive substances, and mycelia are easier to obtain through fermentation culture (Rathore, Prasad, Kapri, Tiwari, & Sharma, 2019). However, many bioactive substances are secondary metabolites whose gene clusters are silent under standard laboratory conditions. Optimization of culture conditions (medium, pH, temperature, etc.) can achieve high biomass yield, but may not increase the content of bioactive substances. Elicitation is one the most effective techniques currently used for improving the bioactive substances production (Ramirez-Estrada et al., 2016). The elicitors are mainly carbon sources, inorganic compounds or physical factors such as oxygen and light (Tian, Dai, Song, Xu, & Ng, 2015). To the best of our knowledge, no work has been published on the elicitation bioactive substances of S. baumii.
In this paper, we described, isolated and cultured the medicinal mushroom S. baumii, and successfully cultivated the fruiting bodies. In addition, since S. baumii, like S. vaninii and S. sanghuang, is known for its medicinal properties, we compared the contents of total polysaccharides, flavonoids, and triterpenoids in mycelia and fruiting bodies of the three species. We also tested the contents of bioactive substances in the elicited S. baumii mycelia.