title: Nitrite metabolism in Debaryomyces hansenii TOB-Y7, a yeast strain involved in tobacco fermentation.
abstract: The Italian cigar manufacturing process includes a fermentation step that leads to accumulation of nitrite and tobacco-specific nitrosamines (TSNA), undesirable by-products due to their negative impact on health. In this study, growth and biochemical properties of Debaryomyces hansenii TOB-Y7, a yeast strain that predominates during the early phase of fermentation, have been investigated. With respect to other D. hansenii collection strains (Y7426, J26, and CBS 1796), TOB-Y7 was characterized by the ability to tolerate very high nitrite levels and to utilize nitrite, but not nitrate, as a sole nitrogen source in a chemically defined medium, a property that was enhanced in microaerophilic environment. The ability to assimilate nitrite was associated to the presence of YNI1, the gene encoding the assimilatory NAD(P)H:nitrite reductase (NiR), absent in Y7426, J26, and CBS 1796 by Southern blot data. YNI1 from TOB-Y7 was entirely sequenced, and its expression was analyzed in different media by Northern blot and reverse transcriptase polymerase chain reaction. The evidence that, in D. hansenii TOB-Y7, YNI1 was transcriptional active also in the presence of high ammonia concentration typical of tobacco fermentation, stimulated the development of an improved process that, on a laboratory scale, was proved to be effective in minimizing nitrite and TSNA accumulation.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università degli Studi di Lecce, Via Monteroni, 73100, Lecce, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Vigliotta
authors.forename: Michele
authors.initials: M
authors.lastname: Di Giacomo
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Carata
authors.forename: Domenica R
authors.initials: DR
authors.lastname: Massardo
authors.forename: Salvatore M
authors.initials: SM
authors.lastname: Tredici
authors.forename: Daniele
authors.initials: D
authors.lastname: Silvestro
authors.forename: Marianna
authors.initials: M
authors.lastname: Paolino
authors.forename: Paola
authors.initials: P
authors.lastname: Pontieri
authors.forename: Luigi
authors.initials: L
authors.lastname: Del Giudice
authors.forename: Dino
authors.initials: D
authors.lastname: Parente
authors.forename: Pietro
authors.initials: P
authors.lastname: Alifano
mesh_terms: D015152:Blotting, Northern; D015139:Blotting, Southern; D019143:Evolution, Molecular; D005285:Fermentation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics; D009572:Nitrite Reductases / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D009602:Nitrosamines / Q000378:metabolism; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D004718:Saccharomycetales / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014026:Nicotiana / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D009573:Nitrites; D009602:Nitrosamines; D012337:RNA, Ribosomal, 18S; D009572:Nitrite Reductases