Formation of Water-Soluble Fluorescent Fractions During Thermal Processing of β-Glucan-Rich Medicinal Mushrooms

Thermal processing of biomass can induce chemical transformations that lead to the formation of fluorescent carbonaceous products. In this study, six β-glucan-rich medicinal mushrooms, Ganoderma lucidum, Cordyceps sinensis, Inonotus obliquus, Lentinula edodes, Grifola frondosa, and Hericium erinaceus, were subjected to mild pyrolytic treatment (200 °C for 3 h) to investigate the formation of water-soluble fluorescent fractions. Physicochemical characterization of aqueous extracts was performed using high-performance liquid chromatography size-exclusion chromatography (HPLC-SEC), fluorescence emission spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and β-glucan quantification. Fluorescence emission spectra revealed species-dependent differences in emission intensity, with the most pronounced signals observed for G. lucidum and C. sinensis. HPLC-SEC analysis showed only minor changes in molecular weight distribution after thermal treatment, suggesting limited polymer degradation. FTIR spectra indicated moderate structural modifications consistent with partial carbonization and chemical rearrangement within the mushroom matrices. Despite the mild processing conditions, measurable increases in fluorescence intensity were observed in several species, indicating the formation of fluorescent carbon-rich molecular structures. These findings demonstrate that moderate thermal treatment of β-glucan-rich fungal biomass can generate water-soluble fluorescent carbonaceous fractions without extensive breakdown of the original polysaccharide matrix. The results provide new insights into thermally induced photophysical changes in medicinal mushrooms and contribute to understanding the formation of fluorescent carbonaceous products from natural biomaterials.