Abstract
The industrial production of most food and probiotic products often requires processing involving high temperatures and physiological stress causing loss of viability of probiotic microbial strains. The viability and stability of probiotic strains is a key determinant of their efficacy during administration in human and animal. Thermotolerance is actually a very important feature for probiotic undergoing industrial processing. This paper aimed at assessing the effect of some mineral salts on the thermotolerance and the probiotic properties of lactobacilli isolated from curded milk produced in Mezam Division, Cameroon. Lactobacilli were isolated by pour plate method on de Man Rogosa and Sharpe (MRS) agar. Lactobacilli were selected based on their ability to suppress in-vitro and in-vivo food borne pathogenic bacteria; Salmonella enterica serovar Enteridis and Esherichia coli. Inhibitory activities against these food borne pathogens were performed by disc diffusion method on Mueller Hinton agar. In-vivo inhibition of Salmonella was achieved using oral administration by gavage of (1.0 × 109 CFU/ml) of selected probiotic strain suspended in sterile water. Thermotolerance was assessed by measuring the survival rate of the strain after heating at various temperatures in the presence and absence of mineral salts. Resistance to bile was determined by measuring the survival rate of probiotics after incubation in the presence of oxgallbille and mineral salts. Two catalase negatives isolates were selected based on their capacity to exhibit inhibitory activities in-vitro and in-vivo against food borne pathogens. They were identified as strain of Lactobacillus casei (LS3) and Lactobacillus plantarum (LM4). These strains exhibited significant reduction (P Salmonella count in caeca swabs of infected chick model. The calcium and magnesium salts increased significantly (P < 0.05) the thermo-tolerance and resistance to bile of probiotic strains studied. These results suggested that calcium and magnesium could be used to monitor the viability of probiotic strains in probiotic products.
Highlights
Probiotics are living microorganisms that play a beneficial role in human and animal health [1]
This paper aimed at assessing the effect of some mineral salts on the thermotolerance and the probiotic properties of lactobacilli isolated from curded milk produced in Mezam Division, Cameroon
Two isolates codified LS3 and LM4 with these characteristics were retained for further studies. They were identified using API 50 CHL BioMerieux kit as strain of Lactobacillus casei and Lactobacillus plantarum. These two strains were selected based on their great capacity to significantly suppress two important food borne pathogenic bacteria, Esherichia coli and Salomonellaentericaserovar Enteridis (Figure 1) common in the several regions of Cameroon
Summary
Probiotics are living microorganisms that play a beneficial role in human and animal health [1]. Numerous research studies have demonstrated the beneficial effect of probiotics on the recovery of intestinal health, including the suppression of pathogens such as Salmonella enterica serovar Typhimuriun [3] [4] [5] [6], Salmonella enteric serovar Enteridis, Campylobacter [7] [8] [9] Staphylococcus aureus [10] [11] [12] [13] and even Helicobacter pylori [14] [15] [16] [17] [18]. The viability of the probiotic strains contained in these foods is an essential criterion for the effectiveness of these functional foods. Probiotic products should contain a fairly large number of viable cells in order to be effective after consumption [25]-[30]
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