Do you eat cheese? Then you have already developed a taste for recombinant organisms. One portion of the cheese making process involves treating milk with rennin or rennet, derived from the fourth stomach (rumen) of calves. The major enzyme present is called chymosin, a protease, used to help curdle the milk and precipitate the curds away from the whey. The production of chymosin from calves was a rate-limiting [local] step in the process. Now (since about 1990), recombinant micoorganisms can produce chymosin [local] on a grand scale and the supermarkets are brimming with cheeses for the consumer.