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This study was performed to investigate inhibitory effect on growth of Staphylococcus aureus and Bacillus cereus in lactic acid, hydrogen peroxide and combination of lactic acid and hydrogen peroxide. The minimun inhibitory concentration (MIC) of lactic acid in Staphylococcus aureus were 2500 ppm at pH 7.0, 1250 ppm at pH 5.5, 6.0 and 6.5, while in Bacillus cereus 625 ppm at pH 5.5 and 6.0, 1250 ppm at pH 6.5 and 7.0, respectively. MICs of hydrogen peroxide in Staphylococcus aureus were 50 ppm at pH 6.0, 75 ppm at pH 6.5 and 7.0, while in Bacillus cereus was 75 ppm at pH 5.0, 5.5 and 6.0, respectively. MICs of combined treatment of lactic acid and hydrogen peroxide in Staphylococcus aureus were 1250 ppm of lactic acid with 25 ppm of hydrogen peroxide and 625 ppm of lactic acid with 50 ppm of hydrogen peroxide. When Bacillus cereus were with 1250 ppm of lactic acid with 50 ppm of hydrogen peroxide and 625 ppm of lactic acid with 75 ppm of hydrogen peroxide at 6.5. The correlations between MICs of lactic acid and hydrogen peroxide in S. aureus and B. cereus obtained through the coefficient of determination (R2). R2 value were 0.9934 and 0.9986, respectively. The inhibitory effect of lactic acid and hydrogen peroxide in S. aureus and B. cereus could be confirmed from the result of this experiment.
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