Probiotic Lactobacilli in Fermented Dairy Products: Selective Detection, Enumeration and Identification Scheme.

Nasim Farahmand,Hamid B Ghoddusi,Jane Sutherland,Labia I I Ouoba,Shahram Naghizadeh Raeisi

doi:10.3390/microorganisms9081600

Nasim Farahmand, Hamid B Ghoddusi + Show 3 more

Open Access

https://doi.org/10.3390/microorganisms9081600

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Journal: Microorganisms	Publication Date: Jul 27, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: London Metropolitan University

Abstract

A selection of 36 commercial probiotic fermented dairy products from UK and Europe markets were evaluated for the numbers, types, and viability of Lactobacillus strains against the stated information on their packages. A comparative study was carried out on selectivity of MRS-Clindamycin, MRS-Sorbitol, and MRS-IM Maltose, to select the right medium for enumeration of probiotic Lactobacillus. Based on selectivity of medium for recovery of the targeted lactobacilli, and also simplicity of preparation, MRS-Clindamycin was chosen as the best medium for enumeration of probiotic Lactobacillus in fermented milks. The results of enumeration of lactobacilli showed that 22 out of a total 36 tested products contained more than 106 colony-forming units/g at the end of their shelf life, which comply with the recommended minimum therapeutic level for probiotics. Rep-PCR using primer GTG-5 was applied for initial discrimination of isolated strains, and isolates, which presented different band profile, were placed in different groups. The isolated Lactobacillus spp. were identified mainly as Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus paracasei by analysis of partial sequences of the 16S ribosomal RNA and rpoA genes.

Highlights

MRS agar, MRS-IM Maltose agar, MRS-Sorbitol agar, and MRSClindamycin agar were used for enumeration of probiotic lactobacilli in 36 probiotic dairy products (Figure 1a–f)
An interesting observation was that on MRS-Clindamycin, Lactobacillus acidophilus gives star shaped, irregular small colonies, and Lb. casei gives larger, regular colonies on MRS-Clindamycin
This study reports that MRS-IM Maltose is not an ideal choice for selective enumeration of lactobacilli since the recovery was low compared with other MRS variants

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Certain dairy products are vehicles by which consumers receive adequate counts of probiotic lactobacilli [1]. Probiotic effects are dependent on the number of viable microbial cells that reach the human gut [2]. Their viability in the product is considered as an important prerequisite for achieving health effects

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