Functional Characteristics of Lactobacillus Strains Isolated from Camel's Milk

Abstract

This study aimed at isolation, identification and evaluation of probiotic potential of Lactobacillus isolates from camel's milk. Thirty four Lactobacillus isolates coded M 1 to M 34 were Gram positive, rods, catalase and oxidase negative and nonspore-forming bacteria. These isolates were identified by biochemical tests and API 50 CH kits. From these, 14 different Lactobacillus isolates (M 1, M 2, M 4, M 5, M 9, M 10, M 12, M 14, M 15, M 18, M 20, M 27, M 29 and M 31) which were tolerant to gastric and intestinal juices in a previous study were now tested for antipathogenic activity which varied according to the Lactobacillus species and the challenged pathogen. All 14 isolates demonstrated significant inhibitory effect against methicillin resistant Staphylococcus aureus (MRSA), Bacillus cereus and moderate to low activity against Salmonella typhimurium and Escherichia coli. When tested for bile tolerance at the concentration of 0.3 to 2.0%, the growth rate of 8 isolates M 2, M 5, M 9, M 10, M 12, M 14, M 18 and M 20 exceeded 60 % in 0.3 and 0.5 % bile. M 2 (L. fermentum) and M 12 (L. plantarum) and M 20 (L. paracasei ssp. paracasei) exhibited the highest growth rates of 82, 79.4 and 78.8 % respectively. At higher levels of 1 and 2% bile, significant reduction (p < 0.05) was observed for all tested isolates except M 9 (L. plantarum) with growth rate of 66.5% at 2% bile. As for cholesterol reduction, M 10 (L. plantarum) and M 15 (L. paracasei ssp. paracasei) had the highest reduction rate of 58.0 and 53.2% respectively, which is comparable to the reference strain L. reuteri DSMZ 20056. Testing adhesion to intestinal epithelial cells and ileal tissues of BALB/c mouse; M 20 (L. paracasei ssp. paracasei) and M 2 (L. fermentum) exhibited highest attachment rate of more than 15 bacterial cells/epithelial cell. SEM images showed variable degrees of bacterial attachment to ileal tissues. These results suggest that camel milk is a rich source for potential probiotic lactobacilli which may be suitable for food and nutraceuticals industries; however, further in vivo investigations are needed.