Vanillin biosynthesis pathway in the vanilla orchid

 

This research project is aimed at elucidating the biosynthetic pathway for vanillin glucoside in the vanilla orchid (Vanilla planifolia).

 

Vanilla is the world’s most popular flavor and therefore one of the most popular plant natural products with an estimated annual worldwide consumption of over 2000 tons. 

Vanillin (3-methoxy-4-hydroxybenzaldehyde) is the main flavor compound in vanilla and is one of the key additives to food products, beverages, perfumery. Vanilin is also an intermediate in the pharmaceutical industry.

 

Production of natural vanillin from pods of V. planifolia is a laborious and slow process. Vanilla pods are harvested 9 to 10 months after hand pollination and then cured for several months to initiate enzymatic processes that break down flavor precursors and develop final flavor compounds. Production of 1 kilogram (kg) of vanillin requires approximately 500 kg of vanilla pods, corresponding to pollination of approximately 40,000 flowers. Nowadays, it is only 1% of the global production of vanillin is derived from vanilla pods.

 

99% of the global production of vanillin is chemically synthesised by processing hydrocarbons primarily of fossil origin. Biotechnologically produced vanillin is an alternative to the synthetic vanillin and can be obtained using microorganisms and cell culture processes.

 

Elucidating the biosynthetic pathway
As vanillin is toxic in high concentrations to living cells, vanillin glucoside is formed in plant cells. Vanillin glucoside is only found in the inner part of the vanilla pod. Although vanillin glucoside seems as a simple molecule, biosynthesis pathway of vanillin still remains to be revealed.

This study has taken three major approaches to elucidate vanillin pathway. Namely, a genomic approach in which we have obtained V. planifolia transcriptome from the pod. These sequences will be used for cloning of candidate genes, expressions and functional studies in yeast.  Secondly, a biochemical approach to investigate intermediate compounds that are involved in biosynthesis of vanillin. For this purpose, C14 and C13 isotope labeled feeding assays were carried out with both L-phenylalanine and p-hydroxybenzaldehyde. Thirdly, a proteomic approach in which soluble proteins from the inner part of the vanilla pod were extracted and will be analyze by LC-MS and MALDI-TOF to obtain a profile of proteins in the inner part of the pod.

 

Publication:

Hansen EH, Møller BL, Kock GR, Bunner CM, Kristensen C, Jensen OR, Okkels FT, Olsen CE., Motawia MS, Hansen J (2009) De novo biosynthesis of Vanillin in Fission yeast (Schizosaccharomyces pombe) and Baker’s yeast (Saccharomyces cerevisiae). Applied and Environmental Microbiology 75: 2765-2774