Bioconversions of Ferulic Acid and p-Coumaric Acid to Volatile Phenols by Halotolerant Yeasts. Studies of Halotolerant Yeasts in Soy Sauce Making. (Part I).

Abstract

Bioconversions of feluric acid (FA) and p-coumaric acid (pCA) to volatile phenols by halotolerant yeasts were studied in the high salt medium such as 15% NaCl; Debaryomyces hansenii, Pichia subpelliculosa, P. anomala, and Candida famata converted FA and PCA to the vinylphenols 4 -vinyl guaiacol and 4-vinyl phenol under static culture (Vinylphenol-producing yeast group), C. versatilis, C. halophila, and C. mannitofaciens to the ethylphenols 4-ethyl guaiacol and 4-ethyl phenol (Ethylphenol-producing yeast group), and C, etchellsii, C. nodaensis, C. halonitratophila, P. farinosa, and Zygosaccharomyces rouxii not to volatile phenols (Volatile phenols non-producing yeast group), respectively. It was indicated that cinnamic acids were converted from FA and PCA to vinylphenols by cinnamate decarboxylase (CDase) (Step 1), and sucessively from vinylphenols to ethylphenols by vinylphenol reductase (VRase) (Step 2). Each CDase and VRase of the yeasts showed different specific activities among the species, and some enzymes were inhibited by catechin. Six species of nitrate-assimilating halotolerant yeasts, `'Candida group III'' were divided from two groups, ethylphenol-producing yeasts and volatile phenol non-producing Yeasts, that supported the results of a chemotaxonomic study of the halotolerant Candida Yeasts by Suzuki et al.