Abstract: The present invention provides methods for changing the composition of a cholesterol-containing foodstuff. The methods comprise the step of culturing a member of the family Tetrahymenidae in a liquid, cholesterol-containing foodstuff under conditions that enable one or more (or all) of the following changes in the composition of the foodstuff: (a) reduction in the level of cholesterol in the treated foodstuff; (b) reduction in the level of saturated fatty acids in the treated foodstuff; (c) increase in the level of unsaturated fatty acids in the treated foodstuff; (d) increase in the level of at least one vitamin D precursor in the treated foodstuff and (e) reduction in the level of at least one protein in the treated foodstuff. The foodstuff can be a dairy product, such as milk or egg yolk.

Abstract: A cell free extract from a ciliate microorganism, including protozoo Tetrahymena, wherein the extract comprises a homogenate a microsomal fraction, a desaturase-enriched fraction or a mixture thereof and, more particularly the invention provides substantially pure enzymes: 7 cholesterol desaturases and 22 cholesterol desaturases. The invention also relates to methods for recovering cholesterol desaturases activities from ciliates, including Tetrahymena, and their use in a production of Vitamin D precursors and analogs from several cholesterol sources.

Abstract: The present invention provides methods for: (a) concentrating cholesterol-desaturase activity in a cell free extract, wherein the cell free extract can be a homogenate fraction, a microsomal fraction or a desaturase-enriched fraction from a Tetrahymenidae family microorganism and (b) decreasing the cholesterol content of a foodstuff of animal origin, such as a dairy product. The methods comprise the step of treating a foodstuff by incubating the same with a cell free extract in a effective amount to enable changes in the foodstuff: (a)reduce the level of cholesterol; and (b) increase the level of at least one desaturated cholesterol derivative: &Dgr;7-dehydrocholesterol, &Dgr;22 dehydrocholesterol and/or &Dgr;7,22 bisdehydrocholesterol.

Abstract: The present invention provides methods for: (a) concentrating cholesterol-desaturase activity in a cell free extract, wherein the cell free extract can be a homogenate fraction, a microsomal fraction or a desaturase-enriched fraction from a Tetrahymenidae family microorganism and (b) decreasing the cholesterol content of a foodstuff of animal origin, such as a dairy product. The methods comprise the step of treating a foodstuff by incubating the same with a cell free extract in a effective amount to enable changes in the foodstuff: (a) reduce the level of cholesterol; and (b) increase the level of at least one desaturated cholesterol derivative: &Dgr;7 dehydrocholesterol, &Dgr;22 dehydrocholesterol and/or &Dgr;7,22 bisdehydrocholesterol.