Influence of a Thermostable Fungal Xylanase Combined With Multi-Enzyme Complexes on the Structure, Physicochemical, and Functional Properties of Dietary Fiber From Hawthorn Pomace.

Effects of xylanase (XynA) in combination with various fibrolytic enzymes on the extraction of soluble dietary fiber (SDF) from hawthorn pomace and on the modification of dietary fiber (DF) were investigated. A high-yield fungal strain (Thermomyces lanugiosus Q231) producing a thermostable xylanase (XynA) was screened, and the purified enzyme exhibited a specific activity of 29,470.70 U/mg. Biochemical characterization revealed that XynA exhibited excellent thermal and pH stability, with broad pH adaptability (6.0-8.5) and more than 60% residual activity below 70°C. Notably, at 65°C, the enzyme retained over 50% of its activity even after 500 min of incubation. The highest SDF yield (14.33%) was achieved using a multi-enzyme system containing 60 U/mL XynA, 60 U/mL cellulase, and 80 U/mL β-glucanase. Additionally, XynA and this enzyme system were employed to modify hawthorn pomace dietary fiber (HDF) to investigate the relationship between structural changes and functional properties. Structural analyses revealed that enzymatic treatment increased fiber crystallinity and generated a porous network. Furthermore, XynA-modified HDF exhibited significantly enhanced water-holding and oil-holding capacities, even surpassing the multi-enzyme treatment. This enzymatic modification with XynA and multi-enzymes markedly improved both the glucose adsorption capacity (GAC) and nitrite ion adsorption capacity (NIAC). These results demonstrate that XynA and the combined enzyme system can effectively increase SDF yield while improving the functional properties of HDF, highlighting their potential for developing high-value dietary fibers.