Characterization and In Vitro Fecal Microbiota Regulatory Activity of a Low-Molecular-Weight Exopolysaccharide Produced by Lactiplantibacillus plantarum NMGL2.

Mengke Yao,Min Zhang,Tiantian Lai,Zhennai Yang

doi:10.3390/foods11030393

Mengke Yao, Min Zhang + Show 2 more

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https://doi.org/10.3390/foods11030393

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Abstract

The exopolysaccharide (EPS) produced by Lactiplantibacillus plantarum NMGL2 isolated from traditional fermented dairy cheese was purified chromatographically with DEAE-Sepharose and Sepharose CL-6B columns. The purified EPS was characterized by various physicochemical methods and in vitro fecal microbiota regulation assay. The results showed that the EPS had a relatively low molecular weight of 3.03 × 104 Da, and it had a relatively high degradation temperature of 245 °C as determined by differential scanning calorimetry. Observation of the EPS by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy revealed a highly branched and tangled fibrous network microstructure with many hollow microtubules and spherical particles. Structural study by 1H NMR spectroscopy suggested that the EPS contained a tetrasaccharide repeating unit with monosaccharide components of β-galactose (4.6%), α-glucose (20.6%), and α-mannose (74.8%). The EPS was highly resistant to hydrolysis of simulated human saliva, gastric, and intestinal juices. Moreover, the EPS beneficially affected the composition and diversity of the fecal microbiota, e.g., increasing the relative abundance of Firmicutes and inhibiting that of Proteobacteria. The results of this study indicated significant bioactivity of this novel low-molecular-weight EPS produced by Lpb. plantarum NMGL2, which could serve as a bioactive agent for potential applications in the food and health care industry.

Highlights

Accepted: 26 January 2022Many species of lactic acid bacteria (LAB) can synthesize exopolysaccharides (EPSs), including capsular polysaccharides (CPS) and slime polysaccharides (SPS) [1], such as Streptococcus thermophilus, Lactobacillus acidophilus, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Lacticaseibacillus casei, and Lactococcus lactis [2]
We reported a novel low-molecular-weight EPS produced by Lpb. plantarum NMGL2 that was purified chromatographically and characterized physicochemically and biologically. 16S rRNA amplification and sequencing analysis were carried out to explore the composition, abundance, and structural changes of the fecal microbiota, including beneficial and harmful bacteria under the intervention of the EPS
The yield of crude EPS produced by Lpb. plantarum NMGL2 was 380 mg/L

Summary

Introduction

Accepted: 26 January 2022Many species of lactic acid bacteria (LAB) can synthesize exopolysaccharides (EPSs), including capsular polysaccharides (CPS) and slime polysaccharides (SPS) [1], such as Streptococcus thermophilus, Lactobacillus acidophilus, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Lacticaseibacillus casei, and Lactococcus lactis [2]. Depending on the composition of the polysaccharides, the EPSs of LAB can be classified into homopolysaccharides and heteropolysaccharides. The repeating units of the EPSs from LAB might be linear or highly branched, with the molecular weight (Mw) of the EPSs up to about 106 Da [3]. These EPSs have been shown to possess various bioactivities, such as antitumor [4], immunomodulation, interfering with adhesion of pathogens, inhibiting proliferation of the human colon cancer cell line, and improving resistance against viral infections [5]. High Mw EPSs were shown to help microbial communities to tolerate extreme temperatures and provide better

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