Bioproduction of terpenoid aroma compounds by microbial cell factories

Terpenoids are important aroma components for food and perfumery products. They belong to a class of chemical compounds structurally defined by their C5 prenyl diphosphate precursors, which are sequentially assembled by specific enzymes. As the flavor and fragrance industry grows, a consequential increase in demand for aroma chemicals stimulates improvements in their production methods on an industrial scale. Traditionally extracted from plants, terpenoids have recently exhibited a marked tendency toward environmentally-friendly production processes, for which biotechnological production through microbial cell factories configures as the best alternative. Genetic engineering of microorganisms enables the synthesis of terpenoids from simple carbohydrates, using the microbe's metabolism as a factory-like machinery system. Renewable materials can be used as primary carbon sources, qualifying the processes as sustainable and economically competitive, both of which are highly desirable for modern industrial production methods. Moreover, the modular biosynthesis of terpenoids out of C5 precursors facilitates the metabolic engineering for the formation of larger and more complex compounds. This review provides an overview of the advancements of biotechnological processes toward microbial production of flavor and fragrance terpenoids.