Effects of cellulose-degrading fungus Penicillium griseofulvum on the structure characteristics and adsorption properties of soluble dietary fiber from Citrus aurantium L

Citrus aurantium L. (CAL) was a potential low-cost source of soluble dietary fiber (SDF). To make full use of this resource, a considerable efficiency cellulose degrading strain ( Penicillium griseofulvum ) was screened from soil humus and used in the modification of CAL-SDF. After fermentation by Penicillium griseofulvum , the structure characteristics and adsorption properties of CAL-SDF were improved. Under the optimum fermentation conditions, the yield of SDF enlarged from 5.47% to 20.0%. Scanning electron microscope (SEM) and Fourier infrared spectroscopy (FTIR) analysis showed that the microstructure became loose and porous after fermentation, unfermented SDF (U-SDF) and fermented SDF (F-SDF) had characteristic intake peaks of polysaccharide . The results of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) showed that the crystallization degree (from 16.50% to 23.15%) of SDF was improved by fermentation, which increased the thermal stability of SDF. The monosaccharide composition and average molecular weight (Mw) results showed that fermentation altered the monosaccharide percentage of SDF as well as significantly reduced the molecular weight (from 576,914 to 112,977 Da). Together, these alterations reduced the water holding capacity (from 11.31 to 1.31 g/g) and oil holding capacity (from 14.24 to 12.86 g/g) of SDF, but significant ( P  < 0.05) increased water solubility (from 89.35% to 92.09%), the glucose dialysis retardation index (GDRI), cholesterol adsorption capacity (CAC) and nitrite adsorption capacity (NIAC). In summary, Penicillium griseofulvum could be used as a potential strain for the modification of the CAL-SDF. Moreover, F-SDF may be used as a functional food component, which will increase CAL's value proposition.