Application of metabolic engineering to vanillin biosynthetic pathways in Vanilla planifolia

Vanilla is the most popular flavor in the world, the most widely used on both a dollar and tonnage basis. Natural vanilla flavor is obtained from beans of the climbing vanilla orchid, Vanilla planifolia. The annual world consumption of vanilla beans, on average, is estimated to be over 2,000 tons (Ranadive 2003, 2006). Vanilla, next to saffron is the most expensive spice. The major flavor compound is vanillin (4-hydroxy-3-methoxybenzaldehyde), although over 250 different other compounds have been isolated from vanilla beans, including 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid and 4-hydroxy-3-methoxybenzoic acid (Guarino and Brown, 1985; Adedji, et al., 1993, Hartman, 1992, 2003; Ranadive, 2003, 2006). Out of about 110 known vanilla species only two are in cultivation, Vanilla planifolia and Vanilla tahitensis, and allowed to be used in food (US FDA regulation, 21CFR 169.175.).