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. 2023 Aug 8;12(16):2988.
doi: 10.3390/foods12162988.

Genome Analysis of Bifidobacterium Bifidum E3, Structural Characteristics, and Antioxidant Properties of Exopolysaccharides

Yingxue Yue  1   2 , Yuqi Wang  2 , Yu Han  1   2 , Yifan Zhang  1   2 , Ting Cao  1   2 , Guicheng Huo  1   2 , Bailiang Li  1   2
Affiliations

Genome Analysis of Bifidobacterium Bifidum E3, Structural Characteristics, and Antioxidant Properties of Exopolysaccharides

Yingxue Yue et al. Foods. .

Abstract

In this study, the antioxidant properties of intact cells (IC), cell-free supernatant (CFS), and cell-free extracts (CFE) and whole genome sequencing of Bifidobacterium bifidum E3 (B. bifidum E3), as well as the structural characteristics and antioxidant properties of EPS-1, EPS-2, and EPS-3, were evaluated. The results revealed that intact cells (IC), cell-free supernatant (CFS), and cell-free extracts (CFE) had potent DPPH (1,1-Diphenyl-2-picrylhydrazyl radical), hydroxyl, and superoxide anion radical scavenging capacities, among which CFS was the best. At the genetic level, we identified a strong carbohydrate metabolism capacity, an EPS synthesis gene cluster, and five sugar nucleotides in B. bifidum E3. Therefore, we extracted cEPS from B. bifidum E3 and purified it to obtain EPS-1, EPS-2, and EPS-3. EPS-1, EPS-2, and EPS-3 were heteropolysaccharides with an average molecular weight of 4.15 × 104 Da, 3.67 × 104 Da, and 5.89 × 104 Da, respectively. The EPS-1 and EPS-2 are mainly comprised of mannose and glucose, and the EPS-3 is mainly comprised of rhamnose, mannose, and glucose. The typical characteristic absorption peaks of polysaccharides were shown in Fourier transform infrared spectroscopy (FT-IR spectroscopy). The microstructural study showed a rough surface structure for EPS-1, EPS-2, and EPS-3. Furthermore, EPS-1, EPS-2, and EPS-3 exhibited potent DPPH, hydroxyl, and superoxide anion radical scavenging capacities. Correlation analysis identified that antioxidant capacities may be influenced by various factors, especially molecular weight, chemical compositions, and monosaccharide compositions. In summary, the EPS that was produced by B. bifidum E3 may provide insights into health-promoting benefits in humans.

Keywords: Bifidobacterium bifidum; antioxidant; exopolysaccharide; genome.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Antioxidant capacities of IC, CFE, and CFS. Values with different superscript letters (a, b, and c) significantly differed at p < 0.05 in the same group.
Figure 2
Figure 2
Circular genome map of B. bifidum E3 (A) COG functional classification of the B. bifidum E3 genome (B) KEGG pathway classification of the E3 genome (C) From the outer circle to the inner circle, the first circle and the second circle represent genes on the positive and negative strands, including CDS, tRNA, rRNA, and other genes; the third circle represents GC content; the fourth circle represents GC skew; where green means GC > 0, and purple means GC < 0, the junction of green and purple is the start point and end point of replication, respectively.
Figure 3
Figure 3
Synthesis of sugar nucleotides (A) and gene clusters (B) of B. bifidum E3.
Figure 4
Figure 4
Antioxidant capacities of cEPS. Values with different superscript letters (a, b, c and d) significantly differed at p < 0.05 in the same group.
Figure 5
Figure 5
Ultraviolet spectroscopy (A) and FT-IR spectroscopy (B) of EPS-1, EPS-2, and EPS-3; Field emission scanning electron microscopes of EPS-1 (C), EPS-2 (D), and EPS-3 (E) at magnifications of 5000× and 10,000×; Congo red determination of EPS-1, EPS-2, and EPS-3 (F).
Figure 6
Figure 6
Scavenging capacities of EPS-1, EPS-2, and EPS-3 on DPPH radicals (A), hydroxyl radicals (B), and superoxide anion radicals (C). Values with different superscript letters (a, b, c and d) significantly differed at p < 0.05 in the same group.
Figure 7
Figure 7
Correlation between chemical composition and antioxidant capacities.
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