Biomolecules are made in the living system and some of the Biomolecules which find applications are made in the laboratory/industry. Biomolecules can be synthesized by using pure chemical methods (synthetic) or pure biological methods or sometimes, a mixture of both chemical and Biological Procedure (semi-synthetic). Biomolecules which are available in the natural environment have been engineered by using synthetic, semisynthetic or pure biological methods which are usually called genetic engineering. But a very novel biological method using the concept of evolution had been developed by scientist Frances Hamilton Arnold, Linus Pauling Professor of Chemical Engineering, Bioengineering and Biochemistry at the California Institute of Technology (Caltech) which is called as Directed Evolution (DE) for the engineering of Protein molecules (Protein Engineering). Development of this technology has been awarded Nobel Prize in Chemistry in 2018.
Directed evolution is an iteration of the natural evolution cycle in a laboratory (Evolution in vitro). Three processes occurred in a natural Evolution: variation between replicators and the variation causes fitness differences upon which selection acts, and accumulated variation is heritable. In DE, a single gene is evolved by iterative rounds of error-prone mutagenesis, screening, followed by amplification. Rounds of these steps are typically repeated, using the best variant from one round as the template for the next to achieve stepwise improvements. The likelihood of success in a directed evolution experiment is directly related to the total library size, as evaluating more mutants increases the chances of finding one with the desired properties (1).
An example of directed evolution with comparison to natural evolution. The inner cycle indicates the 3 stages of the directed evolution cycle with the natural process being mimicked in brackets. The outer circle demonstrates steps in a typical experiment. The red symbols indicate functional variants, the pale symbols indicate variants with reduced function.
Directed evolution is frequently used for protein engineering as an alternative to rational design, but can also be used to investigate fundamental questions of enzyme evolution (1).
Dr. Susanta Pahari is a Professor of Biochemistry in Skyline University Nigeria. He has a PhD. in Biochemistry from University of Calcutta, India.