Effect of Temperature and Carbon Source on the Expression of $\beta$-Galactosidase Gene of Lactococcus lactis ssp. lactis ATCC 7962

  • Kim, Tea-Youn (Department of Food Science and Technology, College of Agriculture, Gyeongsang National University) ;
  • Lee, Jung-Min (Department of Food Science and Technology, College of Agriculture and Life Science, Seoul National University) ;
  • Chang, Hae-Choon (Department of Food and Nutrition, College of Natural Sciences, Chosun University) ;
  • Chung, Dae-Kyun (Department of Genetic Engineering, College of Natural Sciences, Kyung Hee University) ;
  • Lee, Jong-Hoon (Department of Foods and Biotechnology, Kyonggi University) ;
  • Kim, Jeong-Hwan (Department of Food Science and Technology, College of Agriculture, Gyeongsang National University) ;
  • Lee, Hyong-Joo (Department of Food Science and Technology, College of Agriculture and Life Science, Seoul National University)
  • Published : 1999.04.01

Abstract

The effects of growth temperature and a carbon source on the expression of $\beta$-galactosidase gene of Lactococcus lactis ssp. lactis ATCC 7962 (L. lactis 7962) were investigated. At $25^{\circ}C$, L. lactis 7962 had a higher $\beta$-galactosidase activity than cells grown at $30^{\circ}C$ or $37^{\circ}C$, although cells grew most quickly at $37^{\circ}C$ The highest $\beta$-galactosidase activity was observed in cells grown in M17 with lactose (l %) followed by cells grown in a galactose (1 %) medium. L. lactis 7962 exhibited the minimum $\beta$-galactosidase activity in glucose media, indicating catabolite repression. When the cellular levels of $\beta$-galactosidase mRNA were examined using slot blot hybridization, no significant differences were observed between cells grown at $25^{\circ}C$ and cells at $30^{\circ}C$ or $37^{\circ}C$ in the same media. This suggests that the quantity of $\beta$-galactosidase mRNA may not be the reason for the higher $\beta$-galactosidase activities of L. lactis 7962 at $25^{\circ}C$ The level of ccpA (Catabolite Control Protein) transcript remained almost constant during the exponential growth phase irrespective of a carbon sourse.

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