Optimization of Exopolysaccharide Produced by Lactobacillus plantarum R301 and Its Antioxidant and Anti-Inflammatory Activities

Abstract

In this study, the yield of exopolysaccharide (EPS) from Lactobacillus plantarum R301 was optimized using a single-factor experiment and response surface methodology (RSM). After optimization, the EPS yield was increased with a fold-change of 0.85. The significant factors affecting EPS production, as determined through a Plackett-Burman design and Central Composite Design (CCD), were MgSO₄ concentration, initial pH, and inoculation size. The maximum yield was 97.85 mg/mL under the condition of 0.01% MgSO₄, an initial pH 7.4, and 6.4% of the inoculation size. In addition, the EPS exhibited strong antioxidant activity, as demonstrated by its ability to scavenge DPPH, ABTS, and hydroxyl radicals. The scavenging rate was up to 100% at concentrations of 4 mg/mL, 1 mg/mL, and 2 mg/mL, respectively. Moreover, the EPS also exhibited reducing power, which was about 30% that of ascorbic acid when both tended to be stable with the increased concentration. These results suggest that L. plantarum R301 EPS possesses different antioxidant mechanisms and warrants further investigation. In addition to its antioxidant activity, the EPS also demonstrated good anti-inflammatory activity by inhibiting the inflammation induced by lipopolysaccharide (LPS) in RAW 264.7 cells, which could decrease nitric oxide (NO) production and expression of the proinflammatory cytokine Il-6. These findings suggest that L. plantarum R301 EPS could be used as a potential multifunctional food additive in the food industry.

Keywords: Lactobacillus plantarum; anti-inflammatory; antioxidant; exopolysaccharide; postbiotics; response surface methodology.

Figure 1

Results of single-factor optimization of EPS production by L. plantarum R301: (A) carbon sources, (B) carbon concentration, (C) nitrogen source, (D) nitrogen concentration, (E) MnSO₄ concentration, (F) MgSO₄ concentration, (I) fermentation temperature, (G) inoculum size, (H) initial pH of medium, and (J) fermentation time. Different lowercase letters indicate significant differences (p < 0.05).

Figure 2

3D response surface plots and contour plots showing the interactive effects of the (A,D) MgSO₄ concentration and initial pH of medium, (B,E) inoculum size and MgSO₄ concentration, and (C,F) inoculum size and initial pH of medium.

Figure 3

Antioxidant activity of EPS against the following: DPPH radical (A), ABTS radical (B), hydroxyl radical (C), and reducing power (D).

Figure 4

Effect of EPS on the viability of RAW 264.7 cells. Different lowercase letters indicate significant difference (p < 0.05).

Figure 5

Anti-inflammatory effect of EPS: (A) NO production, (B–E) mRNA expression of Inos (B), Nf-κb (C), Cox-2 (D), and Il-6 (E) in EPS-treated RAW 264.7 cells. Different lowercase letters indicate significant difference (p < 0.05).