Evaluation of Probiotic Properties of Pediococcus acidilactici M76 Producing Functional Exopolysaccharides and Its Lactic Acid Fermentation of Black Raspberry Extract

Abstract

This study aimed to determine the probiotic potential of Pediococcus acidilactici M76 (PA-M76) for lactic acid fermentation of black raspberry extract (BRE). PA-M76 showed outstanding probiotic properties with high tolerance in acidic GIT environments, broad antimicrobial activity, and high adhesion capability in the intestinal tract of Caenorhabditis elegans. PA-M76 treatment resulted in significant increases of pro-inflammatory cytokine mRNA expression in macrophages, indicating that PA-M76 elicits an effective immune response. When PA-M76 was used for lactic acid fermentation of BRE, an EPS yield of 1.62 g/L was obtained under optimal conditions. Lactic acid fermentation of BRE by PA-M76 did not significantly affect the total anthocyanin and flavonoid content, except for a significant increase in total polyphenol content compared to non-fermented BRE (NfBRE). However, fBRE exhibited increased DPPH radical scavenging activity, linoleic acid peroxidation inhibition rate, and ABTS scavenging activity of fBRE compared to NfBRE. Among the 28 compounds identified in the GC-MS analysis, esters were present as the major groups. The total concentration of volatile compounds was higher in fBRE than that in NfBRE. However, the undesirable flavor of terpenes decreased. PA-M76 might be useful for preparing functionally enhanced fermented beverages with a higher antioxidant activity of EPS and enhanced flavors.

Keywords: Pediococcus acidilactici; antioxidant; black raspberry; exopolysaccharide; flavors; lactic acid fermentation.

Figure 1

(A) Correlation of the hydrophobicity and coaggregation results of the lactic acid bacteria strains. (B) Adhesion activity of Pediococcus acidilactici M76 in the intestine of Caenorhabditis elegans.

Figure 2

Effect of Pediococcus acidilactici M76 on mRNA expression levels of macrophage-activating factors, such as IL-1β (A), IL-6 (B), IL-12 (C), and TNF-α (D). RAW 264.7 cells were treated with different lactic acid bacteria (LAB) strain fractions for 24 h. Cells treated with media alone were used as the negative control (NC), cells treated with lipopolysaccharide (LPS, 1 μg/mL) were used as the positive control (PC). PA-M76, Pediococcus acidilactici M76; PP-33316, Pediococcus pentosaceus (ATCC 33316); LGG, Lactobacillus rhamnosus GG (ATCC 53103). ^a–e Means with different letters are significantly different (p < 0.05).

Figure 3

(A) Changes in pH, viable cell count, and (B) exopolysaccharide production of the fermented black raspberry extract by Pediococcus acidilactici M76. Cultivation was done for 15 days. log CFU/mL at 25 °C: (■), log CFU/mL at 30 °C: (●), pH at 25 °C: (□), pH at 30 °C: (○).

Figure 4

Changes in antioxidant activity of the fermented black raspberry extract by Pediococcus acidilactici M76. (A) DPPH radical scavenge activity (%). (B) Lipid peroxidation inhibitory activity (%). (C) Radical cation ABTS+ scavenging activity. NfBRE: (□), fBRE: (■). ^a,b Means with different letters are significantly different (p < 0.05).

Figure 5

Biplot of the principal component analysis of volatile compounds from fermented black raspberry extract beverage inoculated with Pediococcus acidilactici M76.