Pathway Engineering

Pathway Engineering

INTRODUCTION

From the genetic viewpoint, the production of a small molecule such as ethanol may well be more complex than production of a protein such as somatotropin. Although proteins are macromolecules, single genes encode them, whereas small molecules must be made by biochemical pathways that require several steps, each catalyzed by a separate enzyme. Thus multiple genes are involved, together with their regulatory systems. Pathway engineering involves the assembly of a new or improved biochemical pathway, using genes from one or more organisms. Most efforts to date have been directed to modifications and improvements of existing pathways, rather than the assembly of completely new synthetic schemes. However, totally novel pathways will no doubt begin to appear over the next few years.

Pathway engineering may be applied both to degradative pathways and to biosynthesis. Engineered bacteria may be used to degrade agricultural waste, pollutants, including industrial chemicals, as well as excess herbicides, weed killers, and so forth, in a process called bioremediation. In addition, microorganisms are used to produce a variety of products including alcohol, solvents, food additives, dyes, and antibiotics. The most efficient pathways are those that convert otherwise useless material into useful products. We will start by considering one such scheme, alcohol fermentation. This process was developed long before modern science and is probably humankind’s earliest venture into biotechnology.