Improvement of foodstuff treatment using a Tetrahymena mutant deficient in hidrolase secretion.

GENTILI HERNÁN; NOSEDA DIEGO GABRIEL; NANI LOURDES; NUDEL CLARA; FLORÍN-CHRISTENSEN JORGE.

Pinamar, Pcia de Buenos Aires

Congreso; Reunion Anual de la Sociedad Argentina de Investigaciones Bioquímicas; 2005

Sociedad Argentina de Investigaciones Bioquímicas

The ciliate Tetrahymena sp. is a free-living eukaryotic organism that has ideal properties for the treatment of milk and egg. These include the ability to bioconvert cholesterol into provitamin D by virtue of the unique occurrence of delta-7 cholesterol desaturase. In addition it acylates sterols, accumulating then in the form of steryl esthers inside intracellular lipids droplets. Because of these properties, it can be employed to eliminate cholesterol from milk, egg yolk and finely ground meat particles. An undesirable trait of Tetrahymena is that it secretes large amounts of hydrolases to the medium, lake lipases, phospholipases and proteases. These enzymes may confer unpleasant sensory properties on the treated foodstuffs. We therefore explored the use of mutant cell lines specifically blocked in hydrolase release. The most efficient mutant, termed MS-1 has been obtained by N-nitrosoguanidine mutagenesis of the wild type cell line. It is a stable homozygous micronuclear mutant. We found that this mutant has reduced extracellular lipase and phospholipase release. Previously it had been shown to lie deficient in extracellular protease activity. This cell allows extended periods of incubation without coagulation of the milk and therefore a more intense cholesterol bioconversion. Thus it appears as an advantageous alternative to the wild type CU-399 which was used in our prior studies.