Partial characterization of a bacteriocin-like inhibitory substance produced by Streptococcus equinus C6I9, a bovine rumen isolate.

Abstract

The present study aimed to evaluate the production and the factors that influence the antimicrobial activity of a bacteriocin-like inhibitory substance (BLIS) produced by Streptococcus equinus C6I9, a bovine rumen isolate. The antagonist activity was evaluated by the spot-on-lawn assay. Antimicrobial activity of the crude extracts obtained using NaCl acidic solution (pH 2, 100 mM) was evaluated along the bacterial growth and in growth medium containing different carbon and nitrogen sources, by agar diffusion method. Crude extract was evaluated regarding temperature stability, storage conditions, and pH sensitivity. S. equinus C619 inhibited both Gram-positive and Gram-negative strains. The crude extract was sensitive to proteinase K, and showed great stability to different temperatures and pH (2 to 12). The presence of meat extract (1.5 g/L) and sucrose (8 g/L) resulted in higher production of BLIS by S. equinus C6I9. The BLIS molecular mass was determined as approximately 3.5 kDa. The results obtained in this study evidenced the production of a broad spectrum activity, thermo- and pH stable BLIS by the ruminal isolate S. equinus C6I9, important features for its biotechnological application.