A 3.6 kb ice nucleation gene (ina) isolated from Erwinia herbicola was placed under control of the galactose-inducible promoter (GAL1) and introduced into Saccharomyces cerevisiae. Yeast transformants showed increased ice nucleation activity over untransformed controls. The freezing temperature of a small volume of water droplets containing yeast cells was increased from approximately -13 °C in the untransformed controls to -6 °C in ina-expressing (Ina+) transformants. Lower temperature growth of Ina+ yeast at temperatures below 25 °C was required for the expression of ice nucleation activity. Shift of temperature to 5-20 °C could induce the ice nucleation activity of Ina+ yeast when grown at 25 °C, and maximum ice nucleation activity was achieved after induction at 5 °C for ∼12 h. The effects of Ina+ yeast on freezing and texturization of several food materials was also demonstrated.
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)