Which organisms are most commonly genetically engineered to create protein factories?

The most common genetically engineered to create protein factories are the bacteria. Genetic engineering involves manipulation of cellular material to create changes in the structure of living organisms.
By altering the DNA of a cell changes the attributes of cells created by later reproduction. Escherichia coli or E. coli are the common hosts for genetic engineering. It is referred to as the model organisms for genetic engineering because it is of shorter base pairs, rapidly-multiplying, and presence of non-coding consequences.

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