For instance, production of contaminating by-products like isovanillin was observed in the modified Escherichia coli (Migula) Castellani and Chalmers (ATCC® 8739™) strain (Kaur and Chakraborty, 2013). Nevertheless, there are several issues associated with de novo vanillin synthesis in genetically engineered organisms. However, this has been achieved by genetically modifying microorganisms to engineer the lacking biosynthetic steps for de novo vanillin biosynthesis (Hansen et al., 2009 Ni et al., 2015). To date, there are no reports of de novo vanillin biosynthesis in microorganisms. Moreover, vanillin exists in a glycosylated form (glucovanillin) in green vanilla pods, where fungal endophytes responsible for vanillin production may reside. This was engineered by incorporating genes involved in glycosylation in vanillin-producing microorganisms like yeast (Kaur and Chakraborty, 2013). Glycosylation of vanillin is another method of reducing vanillin toxicity to microorganisms and increasing vanillin yield.

Using microorganisms to produce vanillin is thus a favored alternative.įungi reportedly have the highest vanillin yield compared to other microorganisms (Table 1) and vanillin yield may well be associated with the ability of microorganisms, in general, to tolerate vanillin toxicity at toxic concentrations, vanillin would be converted into the less toxic products vanillyl alcohol and vanillic acid, which reduces vanillin yield (Kaur and Chakraborty, 2013). Producing vanillin through tissue culture of vanilla plants is also not cost effective given the slow growth rate of the plant and the absence of active vanillin biosynthesis. Additionally, there is a lack of substrate specificity in the reactions due to competing by-product formation in the chemical synthesis of vanillin, reducing the yield of the product (Chakraborty et al., 2017 Kaur and Chakraborty, 2013) and making the process less efficient. Vanilla originated in Central America where it was also used as a flavoring agent the Spanish brought it to Europe around 1520 and vanilla production on Reunion Island started around 1819 (Table 1).Īpart from environmental concerns, chemical synthesis of vanillin, the major vanilla flavor metabolite, is expensive given the cost of ferulic acid (the precursor for a one-step reaction) whereas agricultural waste is a cheap source of ferulic acid and can be used directly for microbial vanillin synthesis (Chakraborty et al., 2017 Kaur and Chakraborty, 2013). Moore, and Vanilla pompona Schiede, Family: Orchidaceae) (Soto-Arenas and Cribb, 2010).

The orchid genus Vanilla (Family: Orchidaceae) consists of 110 species, three of which are cultivated for their flavor-related commercial value ( Vanilla planifolia Jacks. As a first step, fungal endophytes have been isolated from vanilla pods from Reunion Island and found to be involved with the development of the vanilla flavor. Based on this analysis, it is proposed that vanilla plant endophytes are studied and investigated for the presence of possible vanillin and vanilla flavor biosynthetic reactions. Terroir effects on flavor, as observed for vanilla pods, may be due to the presence of microorganisms in the rhizosphere or in the plant itself. Furthermore, studies on a possible role for endophytes may help to elucidate aspects of the vanillin biosynthetic pathway that still are under debate. This could be in the form of complete pathways, or parts of the vanillin pathway, interacting with the plant’s vanilla flavor compounds biosynthesis machinery. Certain fungal endophytes have been reported to produce secondary metabolites previously thought to be produced by the plant such fungi, particularly those isolated from pods, may play a role in the biosynthesis of vanillin and vanilla flavor compounds in the plant. All plants contain several fungal endophytes which do not cause any symptoms of diseases some endophytes are plant-specific and are thought to play a role in the interaction of the plant with its environment. To produce non-synthetic vanillin, fungi are being used for the biotransformation of vanillin precursors into vanillin. Although customers prefer non-synthetic flavors, non-synthetic vanilla extract is approximately 200 times more expensive than its synthetic counterpart. Synthetic pure vanillin lacks complex flavor notes, and thus cannot replace vanilla in high quality products. Non-synthetic vanilla flavor consists of over 250 components, with vanillin being the major one in terms of amount in the pod. A better understanding of the pathways and how they are regulated may lead to better control of the production of the flavor and thus increase the commercial value of the pods. The biosynthesis of vanillin and other vanilla flavor compounds is still not completely understood.

Vanilla flavoring