Nitrite metabolism in Debaryomyces hansenii TOB-Y7, a yeast strain involved in tobacco fermentation.
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.
Vigliotta
Giovanni
G
Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università degli Studi di Lecce, Via Monteroni, 73100, Lecce, Italy.
Di Giacomo
Michele
M
Carata
Elisabetta
E
Massardo
Domenica R
DR
Tredici
Salvatore M
SM
Silvestro
Daniele
D
Paolino
Marianna
M
Pontieri
Paola
P
Del Giudice
Luigi
L
Parente
Dino
D
Alifano
Pietro
P
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*
D005656:Fungal Proteins; D009573:Nitrites; D009602:Nitrosamines; D012337:RNA, Ribosomal, 18S; D009572:Nitrite Reductases