Ethylphenol Formation by Lactobacillus plantarum: Identification of the Enzyme Involved in the Reduction of Vinylphenols

Abstract

Ethylphenols are strong odorants produced by microbial activity and described as in several foods. is a lactic bacterial species able to produce ethylphenols by the reduction of vinylphenols during the metabolism of hydroxycinnamic acids. However, the reductase involved has not been yet uncovered. In this study, the involvement in vinylphenol reduction of a gene encoding a putative reductase () was confirmed by the absence of reduction activity in the knockout mutant. The protein encoded by, VprA, was recombinantly produced in VprA was assayed against vinylphenols (4-vinylphenol, 4-vinylcatechol, and 4-vinylguaiacol) and all were reduced to their corresponding ethylphenols (4-ethylphenol, 4-ethylcatechol, and 4-ethylguaiacol). PCR and HPLC detection methods revealed that the VprA reductase is not widely distributed among the lactic acid bacteria studied and that only the bacteria possessing the gene were able to produce ethylphenol from vinylphenol. However, all the species belonging to the group were ethylphenol producers. The identification of the VprA protein involved in hydroxycinammate degradation completes the route of degradation of these compounds in lactic acid bacteria. The presence of volatile phenols is considered a major organoleptic defect of several fermented alcoholic beverages. The biosynthesis of these compounds has been mainly associated to yeasts. However, the potential importance of lactic acid bacteria in volatile phenol spoilage is emphasized by reports describing a faster ethylphenol production by these bacteria than by yeasts. The genetic identification of the bacterial vinylphenol reductase involved in volatile phenol production provides new insights into the role of lactic acid bacteria on the production of these The development of a molecular method for the detection of ethylphenol-producing bacteria could be helpful to design strategies to reduce the bacterial production of vinylphenols in fermented foods.

Effects of Tetragenococcus halophilus and Candida versatilis on the production of aroma‐active and umami‐taste compounds during soy sauce fermentation

“…As the structure complexity and diversity of these aroma‐active and taste compounds, traditional strategies, e.g. precursors addition, enzyme identification, are difficult and time‐consuming to elucidate the forming pathways of these compounds . Microbes, including Tetragenococcus halophilus , Zygosaccharomyces rouxii and Candida versatilis , are always used as the starters in soy sauce fermentation .…”

“…precursors addition, enzyme identification, are difficult and time-consuming to elucidate the forming pathways of these compounds. [13][14][15][16][17] Microbes,…”

Biotransformation of Monocyclic Phenolic Compounds by Bacillus licheniformis TAB7

“…Cells were then re-suspended in 5 mL of CF buffer. One hundred microliters of this cell suspension were then inoculated into separate 5 mL portions of sterile CF-buffer containing micronutrients (in g/L: 0.01 FeCl 3 ·6H 2 O, 0.2 MgSO 4 ·7H 2 O, and 0.01 CaCl 2 ·6H 2 O), with a final concentration of 0.5 mg/mL of one phenolic acid added from stock solution (12 mg/mL stock solutions prepared by dissolving respective phenolic compound in Microorganisms 2020, 8,26 3 of 12 DMSO). These were then incubated at 30 • C in a Taitec OD monitor (Taitec Co. Ltd., Aichi, Japan) by shaking (200 strokes/min) for up to 48 h. For the control, 0.5 mg/mL of glucose was added instead of a phenolic compound.…”

“…Microorganisms 2020, 8, 26 4 of 12 flow rate was kept at 0.2 mL/min. Analysis was done in negative ion mode.…”

“…Microorganisms 2020, 8, 26 5 of 12 after 15 days of incubation ( Figure 2). The poor ability of TAB7 to transform syringate could perhaps be attributed to the effect of steric hindrance by more than two functional groups on the benzene ring.…”