Cleaner production of vanillin through biotransformation of ferulic acid esters from agroresidue by Streptomyces sannanensis

Abstract

Abstract Vanillin (4-hydroxy-3-methoxybenzaldehyde; C8H8O3) is the major organoleptic compound of vanilla flavor originally obtained from Vanilla planifolia. Attempt has been made for production of vanillin from ferulic acid esters present in wheat bran, the agro-residue. Streptomyces sannanensis MTCC 6637 was used for biotransformation of ferulic acid esters. The key enzymes involving vanillin production were assayed and the products were estimated using thin layer chromatography and high pressure liquid chromatography. Vanillin production was optimized through response surface methodology. Optimum vanillin production (708 mg L−1) was achieved with de-starched wheat bran (10% w/v), sucrose (0.2% w/v), peptone (1% w/v) at pH 7.5, agitation 220 rpm, and temperature 28 °C and fermentation continued for a period of 5 days. The experimental strain converts ferulic acid ester into ferulic acid with the help of ferulic acid esterase. Ferulic acid was catabolized through Coenzyme-A dependent non–β-oxidation (retro-aldol reaction) of ferulic acid. Feruloyal Coenzyme-A synthetase and Enoyl-Coenzyme-A hydratase/aldolase were involved in conversion of ferulic acid into vanillin. Transient formation of vanillic acid from vanillin was found due to steady state expression of vanillin dehydrogenase. To the best of authors’ knowledge this is the first report of vanillin production directly from agroresidue by S. sannanensis.