Functional and health promoting inherent attributes of Enterococcus hirae F2 as a novel probiotic isolated from the digestive tract of the freshwater fish Catla catla

Abstract

Background: Probiotic microorganisms are gaining global importance because of their use in the preparation of a nutraceutical or in the treatment of infections. As per the health industry demand, there is an urgent need for exploring new indigenous probiotic strains with its specific origin due to variation in gut microflora, different food habits and specific host-microbial interactions. The main objective of the present study was to isolate and identify a novel probiotic Enterococcus strain from the gut of Catla catla fish and evaluate its potentiality as a potent probiotic.

Methods: The whole study was designed with the isolation of novel lactic acid bacterial strain from the gut of Catla catla fish with their biochemical and molecular identifications. The potentiality of the isolated strain as a potent probiotic was carried out according to the parameters described in FAD/WHO guidelines for the evaluation of probiotics in food.

Results: The isolated strain was confirmed as Enterococcus hirae F2 on the basis of various biochemical and 16s rRNA gene sequencing methods. Enterococcus hirae F2 was able to survive under highly acidic and bile salt concentration with the ability for the production of lipase and Bsh enzyme. It was also able to survive under simulated gastrointestinal conditions with the inhibition ability of various pathogens. The antioxidant potentiality with the cell surface hydrophobicity and cell aggregation ability confirms its potentiality as a potent probiotic. All the results detail the potency of Enterococcus hirae F2 as a novel probiotic for a safer use.

Discussion: The isolation of Enterococcus hirae with probiotic potential from the gut of fish is a new approach and done for the first time. However, the whole study concluded that the isolated strain might be used as a novel probiotic in the food industry for the production of new probiotic products which imparts health benefits to the host.

Keywords: Acid tolerance; Catla catla; Enterococcus hirae; Gastrointestinal conditions; Probiotic.

Figure 1

(A) Normal MRS + BCP agar plate (B) Growth of lactic acid bacteria on MRS + BCP plate (C) Bile salt hydrolase activity of E. hirae F2 on MRS-DCA-GCA agar plate (D) Zone of lipid hydrolysis on spirit blue agar plate (E) HHD medium plate showing homofermentative E. hirae F2 with green colour colony (F) Gamma-hemolytic activity by E. hirae F2 on blood agar plate.

Figure 2

Route for identification of lactic acid bacteria at genus level (Salminen et al., 2002).

Figure 3

16S rDNA fragment of E. hirae F2 amplified by PCR.

Figure 4. Bar graph showing bile salt tolerance of E. hirae F2 in MRS broth.

Error bars represent SD of the mean values of results from three replicate experiments.

Figure 5. Bar graph showing acid tolerance response of E. hirae F2 at different pH.

Error bars represent SD of the mean values of results from three replicate experiments.

Figure 6. Bar graph showing ability of E. hirae F2 to survive under artificial gastrointestinal tract conditions.

Error bars represent SD of the mean values of results from three replicate experiments.

Figure 7. Bar graph showing antibacterial activity of E. hirae F2 against E. coli, S. aureus, S. typhi, and Pseudomonas spp.

Error bars represent standard SD of the mean values of results from three replicate experiments.

Figure 8. Bar graph showing antioxidant activity of E. hirae F2 against DPPH.

Error bars represent SD of the mean values of results from three replicate experiments.

Figure 9. Bar graph showing relationship between hydrophobicity (%) and auto aggregation ability (%).

Error bars represent SD of the mean values of results from three replicate experiments.

Figure 10. Phylogenetic tree showing relationship between E. hirae F2 and other Enterococcus hirae strains.