title: Bioconversion of tyrosol into hydroxytyrosol and 3,4-dihydroxyphenylacetic acid under hypersaline conditions by the new Halomonas sp. strain HTB24.
abstract: This paper reports the characterization of a Halomonas sp. strain (named HTB24) isolated from olive-mill wastewater and capable of transforming tyrosol into hydroxytyrosol (HT) and 3,4-dihydroxyphenylacetic acid (DHPA) in hypersaline conditions. This is the first time that a halophile has been shown to perform such reactions. The potent natural antioxidant HT was obtained through a C3 hydroxylation on the ring cycle, whereas DHPA was synthesized via the 4-hydroxyphenylacetic acid (HPA) pathway, which has been well described from other bacterial sources. HT was produced first, and then DHPA was detected in the medium accompanied by traces of HPA. HPA involved another pathway resulting from the activity of an aryl-dehydrogenase, which is suggested to be responsible for both tyrosol and hydroxytyrosol oxidation. Maximal HT content (2.30 mM) and maximal DHPA (5.15+/-0.42 mM) were obtained from a culture inoculated in the presence of 20 mM tyrosol and 0.5 g L(-1) yeast extract. Following this, DHPA was quickly degraded into 5-carboxymethyl-2-hydroxymuconic semialdehyde by a 2,3-dioxygenase, finally resulting in succinate and pyruvate. Phylogenetic analysis of the 16S rRNA gene revealed that this isolate was a member of the genus Halomonas. Strain HTB24, with a G+C content of 55.3 mol%, is closely related to Halomonas neptunia DSM 15720(T), 'Halomonas alkaliantarctica' DSM 15686(T) and Halomonas boliviensis DSM 15516(T).
authors.affiliation: Microbiologie et Biotechnologie des Environnements Chauds, Universités de Provence et de la Méditerranée, Marseille, France.
authors.forename: Pierre-Pol
authors.initials: PP
authors.lastname: Liebgott
authors.forename: Marc
authors.initials: M
authors.lastname: Labat
authors.forename: Laurence
authors.initials: L
authors.lastname: Casalot
authors.forename: Agnès
authors.initials: A
authors.lastname: Amouric
authors.forename: Jean
authors.initials: J
authors.lastname: Lorquin
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism; D001482:Base Composition; D001711:Biotransformation; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005516:Food Microbiology; D020632:Halomonas / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007220:Industrial Waste; D008969:Molecular Sequence Data; D010648:Phenylacetates / Q000378:metabolism; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000378:metabolism; D010802:Phylogeny; D019289:Pyruvic Acid; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D019802:Succinic Acid / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D000447:Aldehydes; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D007220:Industrial Waste; D010648:Phenylacetates; D012336:RNA, Ribosomal, 16S; D015102:3,4-Dihydroxyphenylacetic Acid; C005975:3,4-dihydroxyphenylethanol; C011867:4-hydroxyphenylethanol; C015930:2-hydroxy-5-carboxymethylmuconate semialdehyde; C008070:4-hydroxyphenylacetic acid; D019289:Pyruvic Acid; D019802:Succinic Acid; D010626:Phenylethyl Alcohol