What is Evolution? What is Directed Evolution?
To understand directed evolution, it is necessary to first understand evolution. Natural selection, together with a combination of gene-protein interactions, propels evolution. In evolution, certain enzyme functions and enzyme properties are altered, fine-tuned and adapted to the organism's environment. These changes do not work in any particular direction or toward any exact goal, but occur spontaneously in highly specialized forms in response to specific reproduction and survival requirements.
We know this, but we do not know how exactly the interaction processes work. Also, what works well in a cellular environment is not as effective in a non-natural environment for a number of reasons, like substrate insolubility, unstable products or additional chemical reactions. So, natural enzymes that are used in agricultural, medical and industrial applications may not always give reliable results. What are needed are stable enzymes that can stay active for long periods in a non-cellular environment and that can work with a variety of substrates. This is where directed evolution comes in handy.
Directed evolution is a controlled process in synthetic biology that is used to engineer proteins or RNA with certain desirable traits that may or may not be naturally occurring. In this type of protein engineering, scientists work toward a defined goal in a defined way - there may actually be many different ways to reach the defined goal, but researchers chose the one that requires the least effort - and monitor the entire process.