Probiotic Properties of Lactic Acid Bacteria Isolated from the Spontaneously Fermented Soybean Foods of the Eastern Himalayas

Abstract

Spontaneously fermented soybean foods with sticky-textured and umami-flavor are popular delicacies of multi-ethnic communities of the Eastern Himalayas. Even though species of Bacillus have been reported earlier as pre-dominant bacteria, we hypothesized that some lactic acid bacteria (LAB) present in these unique soy-based foods may exhibit probiotic properties. Hence, the present study is aimed to evaluate some probiotic attributes of LAB. A total of 352 bacterial isolates from spontaneously fermented soybean foods of the Eastern Himalayas viz., kinema, grep-chhurpi, peha, peron namsing and peruñyaan were preliminarily screened for survival in low pH, bile salt tolerance, and cell surface hydrophobicity. Finally, eight probiotic LAB were selected and identified, based on the 16S rRNA gene sequencing, as Pediococcus acidilactici Ki20 and Enterococcus faecium Kn19 (isolated from kinema), E. faecalis Gc21 (grep-chhurpi), P. acidilactici Ph32 (peha), E. faecium Pn11 and E. faecalis Pn37 (peron namsing), E. lactis Py03, and E. lactis Py08 (peruñyaan). In vitro probiotic attributes, E. faecium Kn19 (73.67 ± 1.05) and P. acidilactici Ph32 (79.71 ± 0.13%) recorded higher survival ability in acid and bile salt test, respectively. Furthermore, attachment ability of isolates to hydrocarbons showed ≥80% adhesion property with E. faecalis Gc21 (90.50 ± 10.14%) marked the highest degree of hydrophobicity, and P. acidilactici Ki20 showed the higher auto-aggregation and co-aggregation property. LAB strains were able to produce antibacterial activity against pathogenic bacteria. Genetic screening revealed the presence of genes responsible for acid tolerance (groEl, clpL), bile salt tolerance (apf, bsh), adhesion (msa, mub1), and bacteriocin producing genes for pediocin (pedA, pedB) and enterocin (entA, entB). The present study highlighted the probiotic potentials of LAB strains isolated from Himalayan naturally fermented soybean foods that may be developed as a starter or co-starter culture for controlled and optimized fermentation of soybeans.