Abstract
Bile salt hydrolase (BSH) activity, hypo-cholesterolemic effect, and probiotic properties have been reported for Enterococcus strains isolated from animal and human gut and fermented foods but not for strains isolated from environmental niches, like aquatic and terrestrial plants, soil, and water. The present study is the first report on isolation of Enterococcus faecium from rhizospheric soils that harbor the bsh gene, remove cholesterol in vitro, and possess essential and desirable probiotic attributes. Fifteen samples were collected from different sites located in northern, southern, and central regions of India, of which five yielded pure colonies that were named LR2, LR3, ER5, LR13, and VB1. These were identified by 16S rRNA gene sequencing as E. faecium and evaluated for BSH activity, cholesterol-lowering potential in vitro, and probiotic properties. Our results indicated that all the strains were capable of surviving the harsh conditions of the gastrointestinal tract and did not harbor any of the virulence genes. Though all strains showed the presence of bsh and potential for cholesterol removal, E. faecium strain LR13 showed a remarkable cholesterol removal capability and vancomycin susceptibility and possessed most of the desirable and essential attributes of a probiotic. Hence, it seems to be a fairly promising probiotic candidate that needs to be further evaluated in in vivo studies, especially for its hypo-cholesterolemic potential.
Highlights
Elevated serum cholesterol has become a major lifestyle-related disorder that results in high morbidity and mortality worldwide
Fifteen samples of rhizospheric soils were collected from different regions of India to isolate potential probiotic strains from lactic acid bacteria (LAB)
The results of 16S rRNA gene sequencing and homology search using BLAST confirmed that these strains were E. faecium
Summary
Elevated serum cholesterol has become a major lifestyle-related disorder that results in high morbidity and mortality worldwide. De-conjugation of the bile salts by bacterial bile salt hydrolase (BSH) has been reported as an important mechanism that is physiologically associated with the hypo-cholesterolemic effect of probiotics (Begley et al, 2006; Ha et al, 2006; Park et al, 2007). Enterococcus is an important member of LAB, several strains of which have shown numerous health benefits like regulating the gut microbiota, alleviating obesity, allergy, irritable bowel syndrome and diarrhea (Franz et al, 2011), immunomodulation (Nissen et al, 2009), hypocholesterolemic effect (Ejtahed et al, 2011), etc. Recent studies have demonstrated that food-grade enterococci are safe and can be differentiated from the nosocomial pathogenic enterococcal strains (Montealegre et al, 2015). Enterococcal strains that have been designated by regulatory agencies as commercial probiotics include Enterococcus faecalis Symbioflor R 1 (SymbioPharm, Herborn, Germany), Enterococcus faecium SF68 R (NCIMB 10415, Cerbios-Pharma SA, Barbengo, Switzerland), and others (Serio et al, 2010; Franz et al, 2011)
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