Production of vanillin from wheat bran hydrolyzates via microbial bioconversion

Vanillin production through microbial bioconversion of ferulic acid obtained from enzymatic hydrolysis of wheat bran has been studied. The biocatalyst employed was a recombinant E. coli strain containing the genes for the transformation of ferulic acid into vanillin of Pseudomonas origin. The substrate of the bioconversion, performed with resting cells grown on LB, was ferulic acid recovered from the crude bran hydrolyzates with different methods: adsorption on ion exchange resins, liquid-liquid extraction and solid phase extraction. These operations allowed selective recovery of ferulic acid from carbohydrates present in the hydrolizates, thus obtaining, beside pure ferulic acid, an aqueous phase rich in reducing sugars, which was assayed as growth substrate for the E. coli strain. The results obtained open the possibility of using the bran hydrolyzates both as the growth substrate for the strain operating the bioconversion and as the source of ferulic acid to produce vanillin.