RESUMEN
Aims: Evaluation of enzymes responsible for microbial transformation of Curcuma longa to vanillin and quantification of phenolic compounds present during the process. Methodology and results: Yeast strains isolated from fermented beverages using curcumin-yeast extract agar were screened for their ability to transform curcumin to vanillin by evaluating ferulic acid esterase, ferulic acid decarboxylase, and vanillin dehydrogenase activities in growing cultures and cell-free supernatant. Based on bioconversion and enzymatic capabilities of the yeasts, Pichia angusta BT21 was selected for microbial transformation of Curcuma longa to vanillin using submerged fermentation technique under stationary mode. The metabolites were extracted from the transformation medium using solid-phase extraction technique and analyzed by thin-layer chromatography and gas chromatography-flame ionization detector. Phenolic compounds obtained in this research comprised of flavonoids (flavanols, flavones, isoflavones and flavonones), phenolic aldehyde (vanillin, vanillic acid, isoeugenol), simple phenolic (phenol) and phenolic acids (the hydroxybenzoic and the hydroxycinnamic acids) respectively. The research is quite profitable from an industrial point of view, considering the commercial price of vanillin and low cost and availability of C. longa which will eventually reduce the cost of industrial production of vanillin and increase supply. Conclusion, significance and impact of study: Bioprocessing of C. longa by submerged fermentation technique under stationary mode reduces vanillin dehydrogenase activity of the Pichia angusta BT21, thus preventing the degradation of vanillin which subsequently leads to increase in vanillin concentration.