Antimicrobial and enzymatic properties of Bacillus subtilis 3H and Bacillus subtilis 1719 probiotic strain metabolites

Lazarev S.A., Mikhailova N.A.

I.I. Mechnikov Research Institute of Vaccines and Sera, Moscow, Russia

Bacillus subtilis produce a wide range of bioactive compounds rendered promising for the creation of a new generation of probiotic preparations known as metabiotics. Aim of the work was to study the antimicrobial and enzymatic properties of metabolites obtained by deep cultivation of B. subtilis 3H and B. subtilis 1719 strains. Antimicrobial activity against test strains of opportunistic microorganisms was studied using the agar diffusion method. Proteolytic and amylolytic properties were evaluated by the ability to hydrolyze casein and starch. Protein composition of the metabolites was analyzed via polyacrylamide gel electrophoresis according to the Laemmli method. It was found that the studied metabolites' antimicrobial activity is concentrated in the fraction with a molecular weight of <5 kDa and has strain-specific features. B. subtilis 3H metabolites are most active against S. aureus FDA 209P (26±2.1 mm) and C. albicans 927 (21.7±1.7 mm). B. subtilis 1719 metabolites are most active against P. mirabilis 24a (20.7±1.7 mm) and E. coli ATCC 25922 (14±1.1 mm) test strains. Enzymatic activity was manifested in the fraction with a molecular weight >30 kDa. B. subtilis 1719 metabolites had a higher activity, as evidenced by hydrolysis zones on milk (31.7±0.9 mm) and potato (27±0.6 mm) agars. The revealed properties of metabolites open the prospect for further research in order to develop new probiotic preparations.