Production of vanillin from wheat bran hydrolyzates via microbial bioconversion

BACKGROUND: Wheat bran contains a large amount of ferulic acid, which can be released through enzymatic hydrolysis and bioconverted into vanillin. A previous study has shown that ferulic acid purification from bran carbohydrates with the Amberlite IRA 95 resin allowed an increased vanillin molar yield. In this work, alternative ferulic acid recovery methods were proposed and the possibility of exploiting the residual carbohydrate-rich water phase was explored. RESULTS: Ferulic acid was recovered from crude wheat bran hydrolyzate by: (i) a hydrophobic sorbent cartridge (ISOLUTE ENV+): (ii) ethyl acetate extraction; and (iii) the resin previously employed. The highest recovery percentage (95%) was obtained with ISOLUTE ENV+, which also allowed an interesting vanillin molar yield from ferulic acid bioconversion (75% from 0.5 mmol L−1 ferulic acid). The residual water phase was a good growth substrate for the microorganism operating the bioconversion. Cells grown on thismatrix could efficiently bioconvert the recovered ferulic acid to vanillin CONCLUSION: The possibility of efficiently recovering ferulic acid from wheat bran hydrolyzates, bioconverting it into vanillin, and valorizing the sugar-rich exhausted water fraction was demonstrated in this work. The approach allowed the production of a value-added fine-chemical from a food-industry by-product. c 2009 Society of Chemical Industry