Effects of Simulated Gastrointestinal Conditions on Combined Potentially Probiotic Limosilactobacillus fermentum 296, Quercetin, and/or Resveratrol as Bioactive Components of Novel Nutraceuticals.

This study evaluated the effects of simulated gastrointestinal conditions (SGIC) on combined potentially probiotic Limosilactobacillus fermentum 296 (~ 10 log CFU/mL), quercetin (QUE, 160 mg), and/or resveratrol (RES, 150 mg) as the bioactive components of novel nutraceuticals. Four different nutraceuticals were evaluated during exposure to SGIC and analyzed the plate counts and physiological status of L. fermentum 296, contents and bioaccessibility of QUE and RES, and antioxidant capacity. Nutraceuticals with QUE and RES had the highest plate counts (4.94 ± 0.32 log CFU/mL) and sizes of live cell subpopulations (28.40 ± 0.28%) of L. fermentum 296 after SGIC exposure. An index of injured cells (Gmean index, arbitrary unit defined as above 0.5) indicated that part of L. fermentum 296 cells could be entered the viable but nonculturable state when the nutraceuticals were exposed to gastric and intestinal conditions while maintaining vitality. The nutraceuticals maintained high contents (QUE ~ 29.17 ± 0.62 and RES ~ 23.05 mg/100 g) and bioaccessibility (QUE ~ 41.0 ± 0.09% and RES ~ 67.4 ± 0.17%) of QUE and RES, as well as high antioxidant capacity (ABTS assay ~ 88.18 ± 1.16% and DPPH assay 75.54 ± 0.65%) during SGIC exposure, which could be linked to the protective effects on L. fermentum 296 cells. The developed nutraceuticals could cross along the gastrointestinal tract with high concentrations of functioning potentially probiotic cells and bioavailable phenolic compounds to exert their beneficial impacts on consumer health, being an innovative strategy for the co-ingestion of these bioactive components.

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.

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.

Application of dielectric spectroscopy to unravel the physiological state of microorganisms: current state, prospects and limits.

Microbial physiology is an essential characteristic to be considered in the research and industrial use of microorganisms. Conventionally, the study of microbial physiology has been limited to carrying out qualitative and quantitative analysis of the role of individual components in global cell behaviour at a specific time and under certain growth conditions. In this framework, groups of observable cell physiological variables that remain over time define the physiological states. Recently, with advances in omics techniques, it has been possible to demonstrate that microbial physiology is a dynamic process and that, even with low variations in environmental culture conditions, physiological changes in the cell are provoked. However, the changes cannot be detected at a macroscopic level, and it is not possible to observe these changes in real time. As an alternative to solve this inconvenience, dielectric spectroscopy has been used as a complementary technique to monitor on-line cell physiology variations to avoid long waiting times during measurements. In this review, we discuss the state-of-the-art application of dielectric spectroscopy to unravel the physiological state of microorganisms, its current state, prospects and limitations during fermentation processes. Key points • Summary of the state of the art of several issues of dielectric spectroscopy. • Discussion of correlation among dielectric properties and cell physiological states. • View of the potential use of dielectric spectroscopy in monitoring bioprocesses.