Effects of Four Extraction Methods on Structure and In Vitro Fermentation Characteristics of Soluble Dietary Fiber from Rape Bee Pollen

In this study, soluble dietary fibers (SDFs) were extracted from rape bee pollen using four methods including acid extraction (AC), alkali extraction (AL), cellulase extraction (CL) and complex enzyme extraction (CE). The effects of different extraction methods on the structure of SDFs and in vitro fermentation characteristics were further investigated. The results showed that the four extraction methods significantly affected the monosaccharide composition molar ratio, molecular weight, surface microstructure and phenolic compounds content, but showed little effect on the typical functional groups and crystal structure. In addition, all SDFs decreased the Firmicutes/Bacteroidota ratio, promoted the growth of beneficial bacteria such as Bacteroides, Parabacteroides and Phascolarctobacterium, inhibited the growth of pathogenic bacteria such as Escherichia-Shigella, and increased the total short-chain fatty acids (SCFAs) concentrations by 1.63-2.45 times, suggesting that the bee pollen SDFs had a positive regulation on gut microbiota. Notably, the SDF obtained by CE exhibited the largest molecular weight, a relatively loose structure, higher extraction yield and phenolic compounds content and the highest SCFA concentration. Overall, our results indicated that CE was an appropriate extraction method of high-quality bee pollen SDF.

Automated summary

In this study, four methods of extraction were used to obtain soluble dietary fibers (SDFs) from rape bee pollen. The effects of different extraction methods on the structure of SDFs and their in vitro fermentation characteristics were investigated. The results indicated that the extraction methods significantly influenced the composition, molecular weight, surface microstructure, and phenolic compounds content of the SDFs, but had minimal impact on functional groups and crystal structure. Furthermore, all SDFs showed positive regulation on gut microbiota by increasing beneficial bacteria and decreasing pathogenic bacteria, as well as promoting the production of short-chain fatty acids (SCFAs). The SDF obtained by complex enzyme extraction (CE) exhibited the highest quality among all methods.