EFFECT OF MODIFIED MRS MEDIUM ON PRODUCTION AND PURIFICATION OF BACTERIOCIN ST4SA PRODUCED BY ENTEROCOCCUS MUNDTII 

Svetoslav Dimitrov Todorov (USP); Leon M.t. Dicks (SU)

Bacteriocins are ribosomally synthesized antibacterial peptides and are usually active against genetically related species. Bacteriocin ST4SA was produced by Enterococcus mundtii ST4SA. Highest antimicrobial activity (51 200 AU/mL) was recorded after 14 h of growth in MRS broth with optimal production at pH 6.0 or 6.5.  Growth of strain ST4SA in the presence of tryptone, yeast extract, or a combination of the two, yielded 102 400 AU/mL.  An increase in production of peptide ST4SA to 102 400 AU/mL was recorded in the presence of 20.0 g/L fructose, but decreased to 25 600 AU/mL in the presence of lactose (20.0 g/L) or mannose (20.0 g/L) as sole carbon source.  Lower activity (25 600 AU/mL) was recorded when 2.0 g/L K₂HPO₄ was replaced by 2.0 g/L KH₂PO₄ in MRS broth.  An increase of K₂HPO₄ to 10.0 g/L and 20.0 g/L resulted in higher activity (102 400 AU/mL).  Addition of glycerol to MRS broth has a negative effect on peptide ST4SA production.  Production of peptide ST4SA required the presence of magnesium sulphate, manganese sulphate and 5.0 g/L sodium acetate.  Exclusion of tri-ammonium citrate from the medium resulted in reduction of activity to 3 200 AU/mL.  Maximum activity (102 400 AU/mL) was recorded in MRS supplemented with 1.0 ppm Vit. C, DL-6,8-thioctic acid or thiamine, respectively.  Growth of L. ivanovii susbp. ivanovii ATCC 19119 in the presence of peptide ST4SA (12 800 AU/mL) resulted in 99% cell lysis after 18h.