Autor(es):
Ramalho, Patrícia A. 
; Cardoso, M. Helena ; Ramalho, Maria Teresa ; Paulo, Artur Cavaco
Data: 2002
Identificador Persistente: http://hdl.handle.net/1822/2158
Origem: RepositóriUM - Universidade do Minho
Assunto(s): Azoreductase; Non-conventional yeasts
Descrição
Poster apresentado no Annual Workshop COST 847 Textile Quality and Biotechnology, 2, Villa Olmo, Como, Itália, 10-11 Outubro 2002. Several non-conventional ascomycete yeast strains, isolated from dye-contaminated environments, display azo-reductive capabilities. Those strains can therefore decolorize azo dyes, which are widely used in the textile industries. The azoreductase activity has been described and investigated in a wide variety of anaerobic bacterial species, particularly from the intestinal microflora, and also, although more rarely, in aerobic bacteria. The present work describes some characteristics of the azoreductase present in one of the isolated yeast strains. This enzyme activity seems to be constitutive in the microorganism, as the decolourization process is not affected by pre-adaptation of the cells to the tested dyes. The azo reduction activity, measured at constant OD (optical density), has a maximum at the end of the exponential growth phase. For cells collected in this phase, the decolourization profile for the two dyes derived from N,N-dimethylaniline (I and II) presents a plateau between pH 3 and 5, while the analogue dyes derived from beta-naphtol (III and IV) have a maximum at pH 3. The azoreductase activity in resting cells shows a typical saturation kinetics in relation to the concentration of the dye. For dye II, at pH 4.0, a Km of 0,42 mM and a vmáx of 3,4 mmol*h-1*gDW-1 were obtained. Despite the low specificity of this yeast azoreductase, both the initial decolourization rate and the extent of the process are dependent on the dye structure.
