The Screening of Hydrogen Peroxide-Producing Lactic Acid Bacteria and Their Application to Inactivating Psychrotrophic Food-Borne Pathogens

Lactic acid bacteria were isolated from various food samples and evaluated for hydrogen peroxide (H 2 O 2 ) production. Cells suspended in 0.5% (wt/vol) glucose plus 0.5% (wt/vol) lactate (pH 7.0) were incubated for 5 h at 37°C under aeration. Among 193 strains, 27 strains accumulated 201-300 ppm H 2 O 2 , and 4 strains accumulated more than 301 ppm H 2 O 2 in the cell suspensions. Among the 9 high-level H 2 O 2 -producing strains, 8 strains were identified as Lactococcus lactis subsp. lactis . The cell-free filtrate from Lc. lactis subsp. lactis AI 62, which contained approximately 350 ppm H 2 O 2 , was evaluated for antimicrobial activity against Enterococcus faecalis , Ent. faecium , enterotoxigenic Escherichia coli , Listeria ivanovii , Staphylococcus aureus , Yersinia enterocolitica , and Aeromonas hydrophila . After 1 h incubation at 30°C in the cell-free filtrate, the initial viable cell counts of the target bacteria (5.53–6.00 log cfu/mL) were reduced by 0.12-5.00 log units, except in the case of enterococci. The sensitivity varied with the bacterial species and pH. The enterococci were resistant to the treatment. Our results show that H 2 O 2 accumulated by lactic acid bacteria in a cell suspension is very effective in reducing the viable cell count of food-borne pathogens.