The Heat Treatment of a Lactobacilli Probiotic to Derive a Postbiotic Has Minor Effects on the Metabolomic Profile

Lactobacillus rhamnosus CNCM I-3698 (LR98) and L. formosensis CNCM I-3699 (LF99) are two probiotic bacterial strains used in industry in a co-fermentation process to produce a probiotic (Pro) and the associated postbiotic (Post). The latter is produced through inactivation of the viable cells in the Pro by a high-temperature short-time (HTST) treatment. The impact of the inactivation process on the metabolomic profile of the Post was investigated. A growth substrate (Control) was fermented using a co-culture of LR98 and LF99 to produce the Pro and then HTST treated (~105 °C; 5 bar; 7 s) to derive the Post. Analysis of the semi-polar metabolome yielded 1412 unique features, from which 105 compounds were identified. The HTST process decreased the peak area in the Post of most features by <10%. Due to fermentation, an increase (fold change > 2; adjusted-p < 0.05) in the peak area was observed for 29 identified compounds, including 15 with known immunomodulatory, anti-oxidative or antibacterial property. The HTST treatment decreased the peak area of 4 of these compounds by >10% and 25 compounds by <10%. The HTST treatment to yield the Post induced minimal changes in the metabolomic profile, while the fermentation to produce the Pro yielded metabolites with known biological activity.