Production of vanillin from wheat bran hydrolyzates via microbial bioconversion

Aromatic flavors production via biotechnological routes is of great interest as the products can be labeled as natural according to the EU legislation. Vanillin (4-hydroxy-3-methoxybenzaldehyde) is one of the most important and widely used flavour in the food industry. Natural vanillin is obtained from Vanilla planifolia, which, however, can supply only less than 1% of the annual market demand (Walton et al. 2003). The majority of vanillin currently on the market is chemically synthesized from guaiacol or lignin, but the product is of lower quality and cannot be defined as natural (Walton et al. 2000). Biotechnological production of vanillin via microbial bioconversion of substrates such as eugenol or ferulic acid is a feasible alternative way of obtaining vanillin (Priefert et al. 2001). In addition, the possibility of employing agro-industrial by-products such as wheat bran as ferulic acid sources (Mathew et al. 2007) may represent an interesting opportunity of valorising them. Previous studies have shown that resting cells of an Escherichia coli recombinant strain carrying the genes involved in the bioconversion of ferulic acid to vanillin of Pseudomonas origin (E.coli JM109/pBB1) can bioconvert the ferulic acid present in crude wheat bran hydrolizates into vanillin (Di Gioia et al. 2007). Vanillin produced, however, is quickly converted into vanillyl alcohol (Di Gioia et al. 2007), thus reducing the vanillin yield of the process. Aim of this work is to try to increase vanillin molar yield from ferulic acid obtained from wheat bran.