Essential oils: An update on their biosynthesis and genetic strategies to overcome the production challenges

Abstract

Essential oils, secreted by plants, are primarily meant for various physiological, ecological, and defense activities. These oils belong to various classes, i.e., isolates of fatty acids, isoprenoids, and phenolic complexes, and can be secreted by various organs of plants. The essential oil market globally has been predicted to grow at a compound annual growth rate (CAGR) of ~8-10%, and reach a staggering figure in excess of USD ten billion in the next 5 years or so. However, the challenge lies in commercial production, keeping pace with the demand, since their natural production in plants is in considerably low quantities, which depends on ecological conditions and growth stages of the plant. Although several investigations exist in the literature, there is a pressing need for a systematic review of the recent updates, particularly concerning the strategies that facilitate the manufacturing of such indispensable oils. The current chapter focuses on various facets of essential oil production, the associated challenges, and the promise of genetic alteration techniques for enhanced essential oil production. Several distinct perspectives have been considered, such as different sources and mechanisms of essential oil biomanufacturing, including their role in plant defense, the array of isolation procedures, and their wide ranges of beneficial attributes, particularly catering to the therapeutic potential, and challenges and metabolic engineering characteristics. A crucial feature of the current chapter is a critical review, underlining these aspects with a case study, using the commercially valuable sandalwood oil as an example, to emphasize the genetic modification strategies for enhancing sandalwood oil.