Antibacterial Activity of Lactic Acid Bacteria Isolated from Fermented Ethiopian Traditional Dairy Products against Food Spoilage and Pathogenic Bacterial Strains

Abayeneh Girma,Aleka Aemiro,Alessandro Di Cerbo

doi:10.1155/2021/9978561

Abstract

Fermented Ethiopian traditional dairy products containing LAB that show antibacterial activities against various food spoilage and pathogenic bacteria have been used for the preservation of fermented dairy products for a long time. However, there are no comprehensive scientific reports on the antibacterial activity of LAB isolated from various fermented dairy products in Pawe Woreda. The objective of the study was to evaluate the antibacterial activity of LAB isolated from traditionally fermented Ethiopian dairy products against spoilage and pathogenic bacteria. Thirty-five samples of fermented dairy products were collected from three cattle-farming areas of Pawe Woreda. A total of 97 LAB were isolated and screened primarily using the perpendicular streak plate method against 3 Gram-positive and 3 Gram-negative bacterial strains. Out of the 97 strains, 10 were active against at least two of the tested bacteria, of which 7 strains were selected for secondary screening by their broad-spectrum antibacterial activities. The seven in vitro antibacterial activities of the extract ranged from 5 to 16 mm in diameter during the secondary screening. In this study, Z2, Z4, and N2 strains exhibited the highest inhibition zone with broad-spectrum activity against all tested bacteria. The MIC and MBC values range from 0.10 to 0.30 µg/µL and 0.20 to 0.50 µg/µL, respectively. Following morphological, physiological, biochemical, and molecular characteristics, seven potent strains were identified as Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus rhamnosus, Leuconostoc mesenteroides, Streptococcus thermophilus, and Lactococcus lactis. According to the findings of this study, Ethiopian fermented dairy products were the most potent source of bioactive compounds with potential effects against food spoilage and pathogenic bacterial strains.

Highlights

Pathogenic and spoilage microbes must be controlled in a variety of foods to ensure food quality and safety
Lactobacillus 33 (34.0%) was the most dominant while Enterococcus 5 (5.2%) was the least occurring species. ese Lactic acid bacteria minimum bactericidal concentration (MBC) (LAB) were isolated from thirty-five Ethiopian fermented dairy product samples collected from the residents of Pawe Woreda
During the secondary screening, compared to the remaining strains, the results of this study revealed that Z2, Z4, and N2 showed the highest inhibition zones with the broad-spectrum activity of all tested food spoilage and pathogenic bacterial strains, as presented in Supplementary data 2

Summary

Introduction

Pathogenic and spoilage microbes must be controlled in a variety of foods to ensure food quality and safety. Applying native microflora and their antimicrobial products is an alternative technique to chemical additives and spices for preventing changes in organoleptic and nutritional properties of foods [2]. LAB are thought to be beneficial and have long been used as the natural flora in fermented foods. LAB saves serious public health problems and economic losses by producing antimicrobial agents such as bacteriocins, diacetyl, organic acids, carbon dioxide, and hydrogen peroxide [3]. Modern food processing is currently confronted with a challenge in that it seeks to prolong the shelf life and protection of foods by chemical means, while customers prefer minimally processed foods that are free of chemical preservatives. Is has sparked a lot of interest in so-called “green technology,” such as new ways to process and utilize microbial metabolites for biopreservation with minimal processing [4].

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Results

Conclusion