Structural characterisation and cholesterol and bile salts adsorption properties of Ganoderma lucidum dietary fiber

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Abstract

This study prepared Ganoderma lucidum insoluble dietary fiber (GIDF) and soluble dietary fiber (GSDF) via enzymatic methods. The structural and physicochemical properties of GIDF and GSDF were systematically characterized using scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), monosaccharide composition analysis, molecular weight determination, and thermogravimetric analysis (TGA). Under simulated gastrointestinal conditions (pH = 2; pH = 8),GSDF exhibited superior hydration properties and adsorption performance, with maximum adsorption rates and capacities for cholesterol (11.2 mg/g, 29.8 %) and bile salts (1489 mg/g, 34.9 %), surpassing those of GIDF. These enhanced adsorption properties are attributed to GSDF's high viscosity, low molecular weight, low crystallinity, and exceptional hydration capacity.Isothermal adsorption models (Langmuir and Freundlich) revealed that the adsorption mode of GIDF was physical adsorption and exhibited greater compatibility with a reversible multilayer adsorption process whereas GSDF adsorbed cholesterol and bile salts through a chemisorption mechanism mediated by ionic interactions.Both adsorption of fibers conformed to the pseudo-second-order kinetic model. These findings demonstrate the efficacy of GIDF and GSDF in cholesterol and bile salt absorption, providing a scientific foundation for developing novel functional foods targeting hyperlipidemia.