Dynamics of physiological responses of potentially probiotic fruit-derived Limosilactobacillus fermentum in apple and orange juices during refrigeration storage and exposure to simulated gastrointestinal conditions

Abstract

This study evaluated the dynamics of the physiological responses of potentially probiotic fruit-derived Limosilactobacillus fermentum 139 and L. fermentum 263 in apple and orange juice during 28 days of refrigeration storage (4 °C) and when submitted to simulated gastrointestinal conditions. Physiological responses were measured with multiparametric flow cytometry using propidium iodide (PI), carboxyfluorescein diacetate (_cFDA) and bis-1,3-dibutylbarbutiric acid (BOX). Viable counts were enumerated with plate count. L. fermentum strains had sizes of > 30% of cell subpopulations with non-permeabilized membrane and enzymatic activities (viable cells, PI-_CFDA +) in apple and orange juices during storage and viable counts of > 6 log CFU ml^-1. Sizes of cell subpopulations with permeabilized membrane without enzymatic activity (dead cells, PI + cFDA-) were low (< 15%) in apple and orange juices during storage. Sizes of cell subpopulations with non-permeabilized and depolarized membrane (PI-BOX +) were decreased (14%) on day 28 of storage. The sizes of permeabilized and depolarized membrane cell (PI + BOX-) subpopulations were variable among the examined strains in juices during storage. Both strains maintained high PI-cFDA + cell subpopulation sizes (> 35%) after exposure to ileum condition and viable counts of ≥ 5 log CFU/mL. PI-BOX + cell subpopulation sizes were low (< 13%) after exposure to ileum condition. L. fermentum 139 and L. fermentum 263 are capable of maintaining a high population of physiologically active and functional cells in apple and orange juice during 28 days of refrigeration storage and when exposed to gastrointestinal conditions.

Keywords: Flow cytometry; Fruit juice; Limosilactobacillus; Physiological state; Survival.