rennet is a substance used for curdling milk, either as part of cheese-making or to make the dessert junket. Most rennet is of animal origin, but vegetable rennet is used for making some cheeses. More recently, microbial rennets have been developed from moulds such as Rhizomucor miehei and, more importantly, the enzyme chymosin has been grown from genetically modified bacteria, fungi, or yeasts. This manufactured rennet is acceptable to vegetarians and is kosher and halal. It is now used to coagulate up to 90 per cent of US and British cheese.