Extraction optimization, structural characterization of soluble dietary fiber from Morchella importuna, and its in vitro fermentation impact on gut microbiota and short-chain fatty acids

Soluble dietary fiber was extracted from spent Morchella importuna by optimizing the extraction conditions using the response surface method. Response surface analysis results indicated that the extraction yield of MI-SDF reached up to 15.38 +/- 0.16% under the optimized conditions with optimal lye concentration of 2.9%, extraction temperature of 71 degrees C and extraction time of 2 h. The results of scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analyses suggested that M. importuna-derived soluble dietary fiber (MI-SDF) exhibited the typical porous fiber structures, polysaccharide functional groups, and cellulose crystal structure. And MI-SDF was applicable to food processing at in vitro fecal fermentation, MI-SDF significantly increased the abundance and diversity of beneficial bacteria and decreased those of harmful bacteria. The levels of total and individual short-chain fatty acids were significantly increased. This study will provide valuable information for further investigation of MI-SDF.