Abstract:
Nutrition science has evolved from a therapeutic and preventative approach to a focus on diets and food systems. This is how a new interest has appeared in functional foods (fermented milk, fortified yogurt, plant-flavored cream cheese, etc.), food supplements and vitamins.
To adhere to this new trend, the food industry has used organic ingredients to improve the health and well-being of the consumer and above all to strengthen the immune system by adding probiotics, prebiotics and natural additives, for example, adding Aloe vera gel to milk and yogurts. The chemical composition of this plant makes it an excellent substrate for microorganisms’ growth, such as probiotics.
The objective of this research is to study the effect of adding of Aloe barbadensis Miller gel on the lactic flora of sheep milk. To do this, 100 samples of raw sheep milk from Sardi breed were collected in four regions of Morocco: Rabat -Salé - Kenitra, the Great Casablanca-Settat, Marrakech-Safi and Beni Mellal-Khenifra. The enumeration of lactic flora was carried out using the deep seeding method on MRS and M17 media. The isolated lactic acid bacteria (LAB) were identified by classical and molecular methods (16S rRNA sequencing). These strains were tested, using the disk method, for their sensitivity to several antibiotics. The antibacterial effect of Aloe vera gel was also evaluated using the microdilution method in a liquid medium coupled with spreading on a solid medium.
In total, 83 strains of lactic acid bacteria could be identified, from three species. These are Enterococcus ssp (65.06%), Lactococcus ssp (31.32%) and Lactobacillus ssp (3.61%). The antibiotic resistance test carried out on LAB isolated from sheep milk showed that all the enterococci tested are resistant to Oxacilin (OX) and streptomycin with a rate of 100%, 85.71% against Nalidixic acid (NA), 71.42% to Daptomycin (DA) and Erythromycin (E), and 42.85% to Vacomycin (VA). These LAB isolates were all sensitive to Penicillin (P), Gentamycin (CN) and Rifampicin (RD). Some of them showed a low resistance to: Ampicillin (14.28%) and Tetracycline (TE) and Kanamycin (K).
The effect of the Aloe vera gel is remarkable on Enterococcus genus. The species E. Faecalis, E. faecium and E. casseliflavus were completely inhibited at the MIC of around 25µg/ml, while E. durans was only inhibited at the concentration of 50µg/ml. Concerning strains of biotechnological and probiotic interest (Lactobacillus), usually used in the fermentation procedure of cheese and yogurt, are only inhibited at a maximum concentration of 100µl/ml. Its effect is bacteriostatic.
Thus, Aloe vera gel would be a functional food which would allow the consumer to benefit not only from the benefits of this plant, but also from those of lactic acid bacteria, in particular probiotics.
Key words: Sheep milk, lactic flora, 16S rRNA sequencing, probiotics, Aloe vera
