Optimum production, stability, partial purification and inhibitory spectrum of antimicrobial compounds produced by Pediococcus pentosaceus DI.

Abstract

The optimum conditions for production of antimicrobial compounds by Pediococcus pentosaceus DI were studied. The antimicrobial compounds in cell free fermented medium were extracted (methanol-acetone), then tested for inhibitory activity against fourteen bacterial strains and its stability to heating, various pH and proteolytic enzymes. In addition, methanol-acetone extract was partial purified through Sephadex G-100 column and thin-layer chromatography. Production of antimicrobial compounds were maximized when P. pentosaceus DI was grown in lactobacilli MRS containing 0.05% L-cysteine-HCl medium at 30 degrees C for 48 h. The methanol-acetone extract showed relatively broad antimicrobial spectrum including lactic acid bacteria and some spoilage and pathogenic bacteria. Antimicrobial activity of methanol-acetone extract was retained after heating (100 degrees C for 30 min) at pH 2.5 to 6.0 but was lost after treating with several proteolytic enzymes at pH 6.5 and 7.0. Sephadex G-100 column revealed three peaks in methanol-acetone extract. The major peak was eluted at 40 ml and including three fractions, which exhibited inhibitory activity, while the other peaks were principally free from any antimicrobial compounds. Thin-layer chromatography of crude methanol-acetone extract and the three fractions, which exhibited inhibitory activity, showed that there was one main spot with Rf at 0.8.