Tyrosol degradation via the homogentisic acid pathway in a newly isolatedHalomonasstrain from olive processing effluents

Abstract

Aims: To isolate a new Halomonas sp. strain capable of degrading tyrosol, a toxic compound present in olive mill wastewater, through the homogentisic acid (HGA) pathway. Methods and Results: A moderately halophilic Gram‐negative bacterium belonging to the Halomonas genus and designated strain TYRC17 was isolated from olive processing effluents. This strain was able to completely degrade tyrosol (2‐(p‐hydroxyphenyl)‐ethanol), a toxic compound found in such effluent. Tyrosol degradation begins by an oxidation to 4‐hydroxyphenylacetic acid (HPA), which is then converted into HGA by an HPA 1‐monooxygenase, while closest Halomonas species degrade tyrosol through 3,4‐dihydroxyphenylacetic acid (DHPA). In the presence of transition metals, HGA underwent a pH‐dependent abiotic conversion into benzoquinone acetic acid, then into 2,5‐dihydroxybenzaldehyde (gentisaldehyde) and pyomelanin, by oxidative decarboxylation and polymerization, respectively. Conclusions: Tyrosol degradation via HGA by the new Halomonas sp. strain TYRC17 was complete in the absence of trace elements. In their presence, HGA was abiotically converted into gentisaldehyde and pyomelanin. Significance and Impact of the Study: This is the first report on tyrosol degradation via the HGA pathway under hypersaline conditions and on the oxidative decarboxylation of HGA into gentisaldehyde. It underlines the importance of the Halomonas genus in the bioremediation of toxic‐contaminated sites.

Phytochemical profiling as a solution to palliate disinfectant limitations

“…In general, phytochemicals were highly efficient in causing sessile bacteria reduction from surfaces, with the exception of tyrosol and eugenol. Although tyrosol has been described as an antimicrobial agent it can be also converted to phenolic intermediates by bacteria reducing its antimicrobial activity (Brooks et al 2006, Liebgott et al 2007, Liebgott et al 2008). On the other hand, eugenol demonstrated antimicrob ia l effectiveness at low concentrations (10 mM); this was also observed by Ali and coworkers (2005) with eugenol and cinnamaldehyde against Helicobacter pylori.…”

Removal of 4-hydroxyphenylacetic acid from aqueous medium by electrochemical oxidation with a BDD anode: Mineralization, kinetics and oxidation products

“…At industrial level, it is used as intermediate in the production of β-blockers like atenolol and other chemicals. It is a primary product upon oxidation of tyrosol (4-hydroxyphenylethanol), another phenolic compound in OOMW [8,9]. However, little information is available about the degradation of 4hydroxyphenylacetic acid for wastewater treatment.…”

4-Hydroxyphenylacetic acid oxidation in sulfate and real olive oil mill wastewater by electrochemical advanced processes with a boron-doped diamond anode

“…The k 1 values varied between 7.3 × 10 −5 s −1 (R 2 = 0.985) for the 100% (v/v) solution and 2.0 × 10 −4 s −1 (R 2 = 0.992) for 0.050 M Na 2 SO 4 . Assuming that Reaction (14) is verified for BDD( OH), its average content can be estimated as k 1 /k 2 , with k 2 = 7.02 × 10 8 M −1 s −1 , growing from 1.0 × 10 −13 to 2.8 × 10 −13 M. As expected, the substrate decay was much faster by PEF due to the more active OH formed from Reactions (7) and (8). Fig.…”

“…One can infer that the main oxidant in EF and PEF is OH in the bulk. The slightly faster destruction in PEF can then be ascribed to the generation of additional amounts of OH by photolytic Reaction (8).…”

“…4-Hydroxyphenylacetic acid is a typical phenolic component routinely found in OOMW. It is a primary product formed upon oxidation of tyrosol (4-hydroxyphenylethanol), which is a well known phenolic compound in OOMW as well [8,9]. On the other hand, 4-hydroxyphenylacetic acid is useful for the industrial synthesis of various end products like the β-blocker atenolol, among others.…”