Objective

The screening of traditional fermented products is essential for the assessment of safety, security and further development of functional foods for the well-being of human health. The aim of the present study was to isolate and identify bacteria from fermented raw milk samples that exhibit health benefit upon consumption.

Method

In order to confirm the isolates as probiotics, several in-vitro assays were conducted to assess the probiotic properties of isolated bacteria. The initial screening includes tolerance to acid, bile, pancreatin and NaCl. The cell surface properties demonstrate their interaction with mucosal epithelium, which includes hydrophobicity and auto-aggregation assay. Safety assessment was done by performing hemolytic test and antibiotic susceptibility test. The antagonistic activity of probiotic strain was further evaluated against some pathogenic bacteria.

Results

Lactobacillus plantarum isolated from fermented raw milk was preliminarily identified by biochemical tests and further confirmed using 16S rRNA identification. The isolate designated as L. plantarum strain GCC_19M1, demonstrated significant tolerance to low pH, 0.3 % bile, 0.5 % pancreatin and 5 % NaCl. In the presence of simulated gastric juice (at pH 3), the isolate exhibited a survival rate of 93.48 to 96.97 %. Further, the development of ecological niches in the human gut and their successful accumulation has been revealed by auto-aggregation and hydrophobicity properties. Absence of hemolytic activity ensures the non-virulent nature of the strain. L. plantarum strain GCC_19M1 showed susceptibility towards towards gentamicin, tetracycline, kanamycin, meropenem and ceftriaxone, and exhibited an antagonistic effect on pathogenic bacteria.

Conclusion

The obtained results conveyed that L. plantarum strain GCC_19M1 has strong probiotic potential, and its presence in the fermented raw milk products may serve as a potent functional probiotic food.