β‐Ionone: Its Occurrence and Biological Function and Metabolic Engineering

β‐Ionone is a natural plant volatile compound, and it is the 9,10 and 9’,10’ cleavage prod-uct of β‐carotene by the carotenoid cleavage dioxygenase. β‐Ionone is widely distributed in flowers, fruits, and vegetables. β‐Ionone and other apocarotenoids comprise flavors, aromas, pigments, growth regulators, and defense compounds; serve as ecological cues; have roles as insect attractants or repellants, and have antibacterial and fungicidal properties. In recent years, β‐ionone has also received increased attention from the biomedical community for its potential as an anticancer treatment and for other human health benefits. However, β‐ionone is typically produced at relatively low levels in plants. Thus, expressing plant biosynthetic pathway genes in microbial hosts and engineering the metabolic pathway/host to increase metabolite production is an appealing alternative. In the present review, we discuss β‐ionone occurrence, the biological activities of β‐ionone, empha-sizing insect attractant/repellant activities, and the current strategies and achievements used to re-construct enzyme pathways in microorganisms in an effort to to attain higher amounts of the de-sired β‐ionone.