Lactic Acid Bacteria Isolated from Fresh Vegetable Products: Potential Probiotic and Postbiotic Characteristics Including Immunomodulatory Effects.

Fatima Alameri,Mohammad Tarique,Shao-Quan Liu,Ashraf Al-Sbiei,Abdelmoneim Abdalla,Maria Fernandez-Cabezudo,Riyad Obaid,Razan Masad,Basel Al-Ramadi,Mutamed Ayyash,Tareq Osaili

doi:10.3390/microorganisms10020389

Abstract

The ability to perform effectively in the gastrointestinal tract (GIT) is one of the most significant criteria in the selection of potential probiotic bacteria. Thus, the present study aimed to investigate the potential probiotic characteristics of some selected lactic acid bacteria (LAB) isolated from vegetable products. Probiotic characteristics included tolerance to acid and bile, cholesterol-removing ability, bile salt hydrolysis, resistance against lysozyme and antibiotics, production of exopolysaccharides (EPS), antimicrobial and hemolytic activities, and cell surface characteristics (auto-aggregation, co-aggregation, and hydrophobicity). The survival rate of isolates after G120 ranged from 8.0 to 8.6 Log10 CFU/mL. After the intestinal phase (IN-120), the bacterial count ranged from 7.3 to 8.5 Log10 CFU/mL. The bile tolerance rates ranged from 17.8 to 51.1%, 33.6 to 63.9%, and 55.9 to 72.5% for cholic acid, oxgall, and taurocholic acid, respectively. Isolates F1, F8, F23, and F37 were able to reduce cholesterol (>30%) from the broth. The auto-aggregation average rate increased significantly after 24 h for all isolates, while two isolates showed the highest hydrophobicity values. Moreover, isolates had attachment capabilities comparable to those of HT-29 cells, with an average of 8.03 Log10 CFU/mL after 2 h. All isolates were resistant to lysozyme and vancomycin, and 8 out of the 17 selected isolates displayed an ability to produce exopolysaccharides (EPS). Based on 16S rRNA sequencing, LAB isolates were identified as Enterococcus faecium, E. durans, E. lactis, and Pediococcus acidilactici.

Highlights

The gut microbiota have the capacity to interact with human cells, including specific immune cells
Reductions in the viable numbers of most bacterial isolates were noted after the gastric phase (G120), with different levels depending on the isolate
The present results suggest that it is recommend to test the capacity of new lactic acid bacteria (LAB) isolates to survive gastrointestinal tract (GIT) conditions in vitro prior to their being employed in in vivo trials

Summary

Introduction

The gut microbiota have the capacity to interact with human cells, including specific immune cells These interactions yield different health benefits in the host, including regulation of GIT motility, destroying toxins and mutagens, transforming bile acid and steroids, producing vitamins, absorbing minerals, and modulating mucosal and systemic immunity. Probiotics are defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host” [3]. Based on this definition, a microorganism is labeled as probiotic only when there is scientific evidence proving its potential health benefits to the host [4]. The nonviable (killed/dead) cells of probiotics have been reported to exhibit health benefits [5,6] This encouraged the ISAPP to issue a consensus on the definition of postbiotics (nonviable cells) [7]. A postbiotic is defined as a “preparation of inanimate microorganisms and/or their components that confers a health benefit on the host” [7]

Methods

Results

Conclusion