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KMID : 0545120070170040644
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Journal of Microbiology and Biotechnology
2007 Volume.17 No. 4 p.644 ~ p.649
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A Response Surface Model Based on Absorbance Data for the Growth Rates of Salmonella enterica Serovar Typhimurium as a Function of Temperature,NaCl, and pH
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Park Shin-Young
Seo Kyo-Young
Ha Sang-Do
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Abstract
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Response surface model was developed for predicting the growth rates of Salmonella enterica sv. Typhimurium in tryptic soy broth (TSB) medium as a function of combined effects of temperature, pH, and NaCl. The TSB containing six different concentrations of NaCl (0, 2, 4, 6, 8, and 10%) was adjusted to an initial of six different pH levels (pH 4, 5, 6, 7, 8, 9, and 10) and incubated at 10 or 20oC. In all experimental variables, the primary growth curves were well (r2=0.900 to 0.996) fitted to a Gompertz equation to obtain growth rates. The secondary response surface model for natural logarithm transformations of growth rates as a function of combined effects of temperature, pH, and NaCl was obtained by SAS’s general linear analysis. The predicted growth rates of the S. Typhimurium were generally decreased by basic (9, 10)
or acidic (5, 6) pH levels or increase of NaCl concentrations (0-8%). Response surface model was identified as an
appropriate secondary model for growth rates on the basis o coefficient determination (r2=0.960), mean square error (MSE=
0.022), bias factor (Bf=1.023), and accuracy factor (Af=1.164). Therefore, the developed secondary model proved reliable
predictions of the combined effect of temperature, NaCl, and pH on growth rates for S. Typhimurium in TSB medium.
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KEYWORD
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Salmonella Typhimurium, response surface model, growth rates
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