title: Expression of a bacterial ice nucleation gene in a yeast Saccharomyces cerevisiae and its possible application in food freezing processes.
abstract: 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 degrees C in the untransformed controls to -6 degrees C in ina-expressing (Ina(+)) transformants. Lower temperature growth of Ina(+) yeast at temperatures below 25 degrees C was required for the expression of ice nucleation activity. Shift of temperature to 5-20 degrees C could induce the ice nucleation activity of Ina(+) yeast when grown at 25 degrees C, and maximum ice nucleation activity was achieved after induction at 5 degrees C for approximately 12 h. The effects of Ina(+) yeast on freezing and texturization of several food materials was also demonstrated.
authors.affiliation: Department of Food Science and Center for Advanced Food Technology, and Center for Agricultural Molecular Biology, Rutgers University, Cook College, New Brunswick, New Jersey 08901-8520, USA.
authors.forename: W Z
authors.initials: WZ
authors.lastname: Hwang
authors.forename: C
authors.initials: C
authors.lastname: Coetzer
authors.forename: N E
authors.initials: NE
authors.lastname: Tumer
authors.forename: T C
authors.initials: TC
authors.lastname: Lee
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000502:physiology; D005524:Food Technology; D005628:Frozen Foods; D015870:Gene Expression; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D013696:Temperature; D014162:Transfection
chemical_list: D001425:Bacterial Outer Membrane Proteins; C063113:ice nucleation protein