Phenotypic and genomic analysis of inulin consumption by Lactiplantibacillus plantarum strains from Sichuan pickle.

AIMS: To investigate the capability, properties, and molecular mechanism of inulin fermentation by lactic acid bacteria (LAB) from Sichuan pickle. METHODS AND RESULTS: A total of 79 LAB strains were purified from 30 aged Sichuan pickle brine samples, and only 21 Lactiplantibacillus plantarum strains (26.58%, 21/79) derived from 15 samples grew well through utilizing inulin as a carbon source. The fermentation tests through using long-chain inulin (lc-inulin) as a carbon source showed that only 6 L. plantarum strains grew well, while other 15 strains could only utilize short-chain oligofructose (FOS), and thin-layer chromatography analysis evidenced a strain specificity of inulin consumption patterns. Lactiplantibacillus plantarum YT041 is a vigorous inulin fermenter, and whole genome sequencing data revealed that sacPTS1 and fosRABCDXE operons might be associated with the fermentation of FOS and lc-inulin, respectively. CONCLUSIONS: The phenotype of inulin consumption is commonly present in LAB from Sichuan pickle, which is strain-specific and largely depends on their specific ecological niche and degree of polymerization.

Seasonal dynamics of microbiota and physicochemical indices in the industrial-scale fermentation of Sichuan Baoning vinegar.

We investigated the impact of seasons of the year on microbiota and physicochemical indices in industrial-scale fermentation of Sichuan Baoning vinegar. Illumina HiSeq sequencing results showed significant differences (P < 0.05) between the microbiomes of vinegar Pei in every-two seasons, except for bacterial communities between summer and autumn. Total acid, reducing sugar, starch, and alcohol contents of vinegar Pei from the same sampling day of each season were measurably different. Although total acid content in vinegar Pei was similar at the end of fermentation (P > 0.05), the increase in total acidity was highest in the autumn. Acetic acid content in raw vinegar was highest in the autumn (3472.42 mg/100 mL), and lowest in the summer (2304.01 mg/100 mL). This study provides a theoretical basis for the production of Sichuan bran vinegar with consistent quality and provides insights into the quality control of traditional fermented foods.

Exopolysaccharides produced by yogurt-texture improving Lactobacillus plantarum RS20D and the immunoregulatory activity.

The strain RS20D capable of significantly improving yogurt texture was isolated from traditional fermented vegetable products, and identified as Lactobacillus plantarum RS20D. The total exopolysaccharides (EPS) were prepared from reconstituted skim milk fermentation by RS20D, and purified through DEAE-Sepharose CL-6B and Sephadex G-100, and consequently the purified fraction designated as RS-r2 was obtained. The further work aimed to elucidate the structural features of RS-r2 via FT-IR spectrum, HPSEC and monosaccharide composition analysis was carried out. The results showed that RS-r2 was a novel acidic heteropolysaccharide mainly consisted of glucose, galactose and glucosamine in a molar ratio of 2.0:1.5:1. The molecular weight was estimated to be 1.69 × 106 Da. The EPS had a high degradation temperature (250 °C), suggesting its high thermal stability. SEM and AFM analysis of EPS further revealed chain microstructure anchored with many regular spherical shape in aqueous solution. In vitro test showed that total EPS secreted by RS20D could stimulate macrophage RAW264.7 to release NO significantly and up-regulated the gene expression of pro-inflammatory cytokines at the mRNA level. Current study suggested that RS20D could be a potential source of immunoregulatory polysaccharide and may be applied as a functional starter culture to improve yogurt texture in the dairy industry.