Factors Affecting Volatile Phenol Production During Fermentations with Pure and Mixed Cultures of Dekkera bruxellensis and Saccharomyces cerevisiae

Abstract

U radu je ispitan utjecaj etanola i prekursora hidroksicimetne kiseline i vinilnog fenola na biosintezu hlapljivih fenola u fermentacijama s mješovitim i čistim kulturama kvasaca Saccharomyces cerevisiae i Dekkera bruxellensis. Analizirana su tri različita soja D. bruxellensis koja su pokazala jedinstveni profil proizvodnje hlapljivih fenola u fermentacijama s mješovitom i čistom kulturom kvasaca. Rezultati su pokazali da je u biosintezi s mješovitom kulturom, u usporedbi s čistom kulturom D. bruxellensis, nastalo manje vinilnog fenola, a više etilnog fenola. Prekursori vinilnog fenola značajno inhibiraju rast kvasca S. cerevisiae te proizvodnju etilnog fenola. Geni što kodiraju enzime kumarat dekarboksilazu i vinilfenol reduktazu u kvascu D. bruxellensis pokazuju jači odziv na prekursore vinilnog fenola u usporedbi s hidroksicimetnom kiselinom. Veće su koncentracije vinilnog fenola u stanicama kvasaca imale jači citotoksični učinak od hidroksicimetne kiseline. Utvrđeno je također da su male koncentracije etanola potakle veću proizvodnju hlapljivih fenola u fermentacijama s kvascima S. cerevisiae i D. bruxellensis, što je potvrđeno i ekspresijom gena što kodiraju kumarat dekarboksilazu u kvascu D. bruxellensis.The paper examines the impact of ethanol, and hidroxycinnamic and vinylphenol precursors on the production of volatile phenols in fermentations of mixed and pure cultures of yeasts Saccharomyces cerevisiae and Dekkera bruxellensis. Three different D. bruxellensis strains were examined and they all showed a unique volatile phenol production pattern in the fermentations of pure and mixed cultures. Generally, the results showed that in mixed culture fermentations less vinylphenols and more ethylphenols were produced in comparison with D. bruxellensis pure culture fermentations. Vinylphenol precursors significantly inhibited the growth of S. cerevisiae and the production of ethylphenols. Nevertheless, it was found that D. bruxellensis genes encoding for enzymes coumaric acid decarboxylase (CAD) and vinylphenol reductase (VPR) are more responsive to vinylphenol precursors in comparison with hidroxycinnamic acids. Consequently, higher concentrations of vinylphenols in the cell were found to be more cytotoxic than hidroxycinnamic acids. In general, low ethanol concentrations induced higher production of volatile phenols by S. cerevisiae and D. bruxellensis. This was confirmed with the expression pattern of gene encoding for CAD of D. bruxellensis