ABSTRACT

Milk and egg are important components of the diet   of human population worldwide. However, they contain cholesterol, which has been implicated in cardiovascular disease. The non-pathogenic ciliate Tetrahymena has a unique set of enzymes that converts cholesterol into pro-vitamin D, including delta-7 and delta-22-cholesterol-desaturases. Here we present different methods by which this enzyme system can be utilised for decreasing cholesterol levels in foodstuffs and simultaneously enrich them in provitamin D compounds. So far no method has such property  of reducing cholesterol from food, while enhancing its nutritional value. The methods we describe include the use of live Tetrahymena thermophila added to milk and egg suspensions. This procedure can reduce by half the initial cholesterol contents in a single treatment. We have also used cell free extracts which have typical transformations rates of cholesterol of 50 ng min^-1 mg^-1 in milk and 680 ng min^-1 mg^-1 in egg suspensions. We show evidence that both enzymes are cytochrome b5 dependent and present possible clues for perfecting the system through the use of recombinant DNA techniques.