Effect of nitrogen and carbon sources on Indigo and Congo red decolourization by Aspergillus alliaceus strain 121C.

The decolourizing ability of Aspergillus alliaceus 121C was investigated on solid medium. The effects of nitrogen (N), carbon (C) sources and supplements on the decolourization of Indigo and Congo red dyes were studied. It has been shown that both the nature and the quantity of available N- and C-sources exert an influence on growth and decolourization. For the six N-sources (NH(4)Cl, Diammonium Tartrate, urea, malt extract, peptone and yeast extract) tested for Congo red decolourization, 8mM yeast extract provided the higher decolourized zone diameter (80 mm) and colony diameter (80 mm). 12 mM urea provided the higher decolourized zone diameter (76+/-2mm) and colony diameter (80 mm) for Indigo decolourization. For the C-sources tested (glucose, starch, glycerol and lactose), above 12.5mM of glucose and 62.5mM of starch provided the higher decolourized zones diameters of 80 mm and 77+/-3mm for Indigo and Congo red, respectively. When the fungi was grown in liquid medium containing optimum carbon and nitrogen sources supplemented with oak sawdust and wheat bran, more than 98.6% and 98% of colour removal are obtained for Indigo and Congo red dyes, respectively. The detection of ligninolytic enzymes proved that laccase and lignine-peroxidase (LiP) are the two enzymes responsible of the decolourization of the two dyes.