C13-apocarotenoids biosynthesis with engineered microbes

C13-apocarotenoids are volatile organic compounds naturally derived from the oxidative cleavage of carotenoids. These small molecules form unique aromas in flowers, fruits, and plants. They are highly valued compounds in the flavor and fragrance industry. The microbial production of C13-apocarotenoids, such as β-ionone, α-ionone, and pseudoionone, is an emerging and promising approach with inherent advantageousness of scalable output to reach the goals as stated in the United Nations Sustainable Development Goals. Many engineering efforts have been implemented continuously but very few of them proved to be successful in achieving product titer at the grams-per-liter level with the least accumulated amount of precursor carotenoids and byproducts. The efficiency of oxidative cleavage of carotenoids conducted by carotenoid cleavage dioxygenases is suggested to be the critical metabolic node to reconstruct an economically viable C13-apocarotenoids biosynthetic pathway. In this regard, we review recent advances in improving microbial biosynthesis of C13-apocarotenoids by protein and metabolic engineering. The potential strategies that could be implemented further to achieve efficient C13-apocarotenoid production are also discussed.