In
this study, the fermentation characteristics of high
rhamnogalacturonan
I pectic polysaccharides (RGI) and free-radical degraded RGI (DRGI)
were evaluated by a human fecal batch-fermentation model, and their
structural properties were also investigated. As a result, the M
w of RGI decreased from 246.8 to 11.6 kDa, and
the branches were broken dramatically. Fermentation showed that RGI
degraded faster and produced more acetate and propionate than DRGI.
Both of them reduced the Firmicutes/Bacteroidetes ratio and promoted
the development of Bacteroides, Bifidobacterium, and Lactobacillus, bringing benefits to the gut ecosystem. However, the composition
and metabolic pathways of the microbiota in RGI and DRGI were different.
Most of the dominant bacteria of RGI (such as [Eubacterium]_eligens_group) participated in carbohydrate utilization, leading to better performance
in glucolipid metabolism and energy metabolism. This work elucidated
that large molecular weight matters in the gut microbiota modulatory
effect of RGI-type pectic polysaccharides in vitro.
Canned citrus is a major citrus product that is popular around the world. However, the canning process discharges large amounts of high-chemical oxygen demand wastewater, which contains many functional polysaccharides. Herein, we recovered three different pectic polysaccharides from citrus canning processing water and evaluated their prebiotic potential as well as the relationship between the RG-I domain and fermentation characteristics using an in vitro human fecal batch fermentation model. Structural analysis showed a large difference among the three pectic polysaccharides in the proportion of the rhamnogalacturonan-I (RG-I) domain. Additionally, the fermentation results showed that the RG-I domain was significantly related to pectic polysaccharides’ fermentation characteristics, especially in terms of short-chain fatty acid generation and modulation of gut microbiota. The pectins with a high proportion of the RG-I domain performed better in acetate, propionate, and butyrate production. It was also found that Bacteroides, Phascolarctobacterium, and Bifidobacterium are the main bacteria participating in their degradation. Furthermore, the relative abundance of Eubacterium_eligens_group and Monoglobus was positively correlated with the proportion of the RG-I domain. This study emphasizes the beneficial effects of pectic polysaccharides recovered from citrus processing and the roles of the RG-I domain in their fermentation characteristics. This study also provides a strategy for food factories to realize green production and value addition.
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