Pilot Study: Nutritional and Preclinical Safety Investigation of Fermented Hispidin-Enriched Sanghuangporus sanghuang Mycelia: A Promising Functional Food Material to Improve Sleep

The Liquid-Fermentation Formulation of Sanghuangporus sanghuang Optimized by Response Surface Methodology and Evaluation of Biological Activity of Extracellular Polysaccharides

Sanghuangporus sanghuang is a rare fungus growing on mulberry trees that has immense medicinal value. This study aimed to optimize the liquid-fermentation-media formulation and culture conditions for large-scale culturing of S. sanghuang by performing one-way testing and response surface methodology. The antioxidant and anticancer activities of the extracellular polysaccharides from S. sanghuang were also analyzed. The optimal formulation and growth conditions for S. sanghuang were as follows: glucose, 30.2 ± 0.37 g/L; yeast extract, 14.60 ± 0.05 g/L; dandelion powder, 1.24 ± 0.01 g/L; shaker speed, 150 r/min; and temperature, 25 °C. We obtained 13.99 ± 0.42 g/L of mycelium biomass by culturing S. sanghuang for 15 days with the optimized formulation. This was 2-fold higher than the mycelial mass obtained with the sub-optimal formulation. The extracellular fungal polysaccharides showed significant antioxidant activity against ABTS and DPPH free radicals, and significantly reduced the in vitro growth and survival of several cancer cell lines. The anticancer activity of the extracellular fungal polysaccharides was significantly higher in the human glioma cells than in other cancer cell lines. In summary, this study optimized the liquid media formulation and conditions for the large-scale culturing of S. sanghuang. Furthermore, the extracellular polysaccharides from S. sanghuang showed significant antioxidant and anticancer activities.

Research on the Interaction Mechanism and Structural Changes in Human Serum Albumin with Hispidin Using Spectroscopy and Molecular Docking

The interaction between human serum albumin (HSA) and hispidin, a polyketide abundantly present in both edible and therapeutic mushrooms, was explored through multispectral methods, hydrophobic probe assays, location competition trials, and molecular docking simulations. The results of fluorescence quenching analysis showed that hispidin quenched the fluorescence of HSA by binding to it via a static mechanism. The binding of hispidin and HSA was validated further by synchronous fluorescence, three-dimensional fluorescence, and UV/vis spectroscopy analysis. The apparent binding constant (Ka) at different temperatures, the binding site number (n), the quenching constants (Ksv), the dimolecular quenching rate constants (Kq), and the thermodynamic parameters (∆G, ∆H, and ∆S) were calculated. Among these parameters, ∆H and ∆S were determined to be 98.75 kJ/mol and 426.29 J/(mol·K), respectively, both exhibiting positive values. This observation suggested a predominant contribution of hydrophobic forces in the interaction between hispidin and HSA. By employing detergents (SDS and urea) and hydrophobic probes (ANS), it became feasible to quantify alterations in Ka and surface hydrophobicity, respectively. These measurements confirmed the pivotal role of hydrophobic forces in steering the interaction between hispidin and HSA. Site competition experiments showed that there was an interaction between hispidin and HSA molecules at site I, which situates the IIA domains of HSA, which was further confirmed by the molecular docking simulation.

Transcriptome Analysis Reveals the Putative Polyketide Synthase Gene Involved in Hispidin Biosynthesis in Sanghuangporus sanghuang

Hispidin is an important styrylpyrone produced by Sanghuangporus sanghuang. To analyze hispidin biosynthesis in S. sanghuang, the transcriptomes of hispidin-producing and non-producing S. sanghuang were determined by Illumina sequencing. Five PKSs were identified using genome annotation. Comparative analysis with the reference transcriptome showed that two PKSs (ShPKS3 and ShPKS4) had low expression levels in four types of media. The gene expression pattern of only ShPKS1 was consistent with the yield variation of hispidin. The combined analyses of gene expression with qPCR and hispidin detection by liquid chromatography-mass spectrometry coupled with ion-trap and time-of-flight technologies (LCMS-IT-TOF) showed that ShPKS1 was involved in hispidin biosynthesis in S. sanghuang. ShPKS1 is a partially reducing PKS gene with extra AMP and ACP domains before the KS domain. The domain architecture of ShPKS1 was AMP-ACP-KS-AT-DH-KR-ACP-ACP. Phylogenetic analysis shows that ShPKS1 and other PKS genes from Hymenochaetaceae form a unique monophyletic clade closely related to the clade containing Agaricales hispidin synthase. Taken together, our data indicate that ShPKS1 is a novel PKS of S. sanghuang involved in hispidin biosynthesis.

Mycelial inhibitory effects of antagonistic fungi, plant essential oils and propolis against five phytopathogenic Fusarium species

Fusarium spp. are considered as one of the most devastating plant pathogenic fungi worldwide. In this study, the effect of essential oil (EO) of Mentha longifolia, M. spicata, Achillea sp. and Foeniculum vulgare, ethanolic extract of Propolis (EEP), and Trichoderma harzianum T447 and T. hamatum T622 was investigated against five phytopathogenic Fusarium species. The results showed that the fungal species, the type of EO, and concentrations play a substantial role in inhibiting the mycelial growth of Fusarium spp. GC-MS analysis of the EOs showed that the piperitone oxide and cis-piperitone oxide were found as the main components of M. longifolia. Our results also revealed that EEP possessed the growth inhibitory effect against Fusarium spp. It was observed that the extracellular secretions of T. harzianum T447 showed very high inhibition against the fungi. Our results highlighted the need for further research to apply them as a safe alternative to the chemical pesticides.