Background and purpose: Lactic acid bacteria (LAB) play an important role in human and other organisms life. Some of LABs kill pathogenic and other harmful microorganisms. Enterococcus are, gram-positive, catalase-negative, cocci forming, non-sporogenesis, and facultative anaerobic bacteria. This study was done to identify and isolate possible probiotic bacteria with benefits to human health from Persian oak sap (Quercus brantii var. persica). The aim was to identify beneficial bacteria for plant pathogenic biological control and industrial applications.

Materials and methods: LABs were identified using conventional methods, including culture dependent methods and 16S rRNA sequencing method. Antibiogram analysis was performed and the presence of virulence genes, including efaA (endocarditis antigen), as, ace, esp and gelE was examined by PCR.

Results: It was found that out of 285 colonies, 160 (56.1%) were catalase-negative and gram-positive. Results of 16S rRNA sequencing showed that the bacteria isolated bacteria belong to the Enterococcus Faecium species. E. faecium strains of this study were sensitive to a number of clinically important antibiotics such as vancomycin, ampicillin, ciprofloxacin, and nitrofurantoin. Two strains of E. faecium bacteria, one with the ability to produce Co₂ from glucose (KX185054) and one with no Co₂ production ability (KX185055) were identified. The 16S rRNA sequence of identified strains were deposited in NCBI database. PCR amplification did not amplify virulence genes except efaA (endocarditis antigen).

Conclusion: In this study, two different E. faecium strains were isolated from the oak which can be good candidates for probiotics and biological control.