Production of Industrially Relevant Isoprenoid Compounds in Engineered Microbes

Isoprenoids are the largest class of natural compounds and have extremely diverse chemical and functional properties. They are involved in many different cellular processes, including hormonal regulation, signalling, pest/pathogen defence and redox status. They also provide many of the colours, flavours and aromas found in biology. The diversity of isoprenoids lends them to a wide variety of biotechnological applications, both by exploiting their myriad natural functions and by using them as industrial chemicals/chemical feedstocks. These applications range from fine chemicals (pharmaceuticals, nutraceuticals, antimicrobials) through mid-volume (flavours, fragrances, colourants, fuel additives) and bulk (fuels, synthetic polymers, agricultural chemicals, etc.) products. However, in their natural context, individual isoprenoids are not usually found at sufficient abundance for industrial use. Moreover, extraction and/or purification may be difficult and/or expensive, or production may be highly variable, making industrial production processes challenging or impossible. Artificial synthesis is often not possible due to complexity, expense or other chemical properties/requirements. Consequently, there is a strong movement towards bioengineering of microbes for production of these valuable compounds in controlled fermentation conditions. Here we consider the requirements for developing economically viable isoprenoid production bioprocesses as well as the current state of the art in engineering production in microbes. We also discuss some of the challenges we face in bringing these technologies to the market.