Synergistic effects of probiotic Leuconostoc mesenteroides and Bacillus subtilis in malted ragi (Eleucine corocana) food for antagonistic activity against V. cholerae and other beneficial properties

Abstract

Finger millet (Elucine corocana), locally known as ragi, and probiotics have been recognized for their health benefits. In the present work we describe novel probiotic ragi malt (functional food) that has been prepared using ragi and probiotic Leuconostoc mesenteroides (Lm) and Bacillus subtilis natto (Bs), alone and in combination, for antagonistic activity against Vibrio cholerae (Vc). In vitro studies using pure cultures showed that each probiotic strain (Lm or Bs) was able to inhibit the planktonic growth of Vc as well as its ability to make biofilms and adhere to extracellular matrix proteins (fibronectin, Fn) that may function in vivo as initial ports of entrance of the pathogen. Interestingly, the combination of both probiotic strains (Lm plus Bs) produced the strongest activity against the Vc. When both cultures were used together in the ragi malt the antimicrobial activity against Vc was enhanced due to synergistic effect of both probiotic strains. The inclusion of both probiotic strains in the functional food produced higher amounts of beneficial fatty acids like linoleic and linolenic acid and increased the mineral content (iron and zinc). The viability and activity of Lm and Bs against Vc was further enhanced with the use of adjuvants like ascorbic acid, tryptone, cysteine hydrochloride and casein hydrolysate in the ragi malt. In sum, the intake of probiotic ragi malt supplemented with Lm and Bs may provide nutrition, energy, compounds of therapeutic importance and antagonistic activity against Vc to a large extent to the consumer.

Keywords: Bacillus subtilis; Functional food; Lactic acid bacteria; Synergistic probiotics; Vibrio cholerae.

Fig. 1

a Inhibition of the planktonic growth of V. cholerae by probiotic B. subtilis and L. mesenteroides. (Black circle) Bs plus Lm, (Black square) Bs and (Black up-pointing triangle) Lm. b Inhibition of V. cholerae binding to ECM proteins by probiotic Bs and Lm (Black circle) Bs plus Lm, (Black square) Bs and (Black up-pointing triangle) Lm. c Inhibition of V. cholerae biofilm formation by cell-free supernatants of probiotic Bs and Lm. (Black circle) Bs plus Lm, (Black square) Bs and (Black up-pointing triangle) Lm