Effects of glucose and NH 4+ concentrations on sequential dye decoloration by Trametes versicolor

Abstract

Mycelial pellets of Trametes versicolor, grown at initial glucose and ammonium tartrate concentrations of 10 g/l (56 mM) and 0.442 g/l (2.4 mM) respectively, decolorized successive additions of the same dye (Amaranth) and of different dyes and dye mixtures. Decoloration commenced by Day 3 and all dyes were decolorized at high rates during the next 12 days. Glucose was consumed at a steady rate and was depleted by Day 15. Dyes added after this time were decolorized at decreased rates and decoloration ceased at Day 18. Replenishing glucose levels to 5 g/l restored the decoloration rate. Above about 0.13 g/l of glucose, the rate of decoloration was constant and when less than 0.13 g/l, the rate of decoloration decreased as glucose concentration decreased. Decolorizing cultures used glucose at a higher rate than when no dye was added. Ammonium was depleted at Day 4 whether dye was initially present or absent. Rapid decoloration was maintained at 0.086 g/l NH 4 +, but was inhibited at 0.86 g/l NH 4 +. When NH 4 + was increased from 0.086 to 0.86 g/l in actively decolorizing cultures, decoloration ceased. This requirement for nitrogen-limitation has been reported during decoloration by ligninolytic cultures of Phanerochaete chrysosporium and suggests that decoloration by T. versicolor may be a similar process. However, the culture conditions used in this study repress ligninolysis and dye decoloration by P. chrysosporium, indicating that dye decoloration by T. versicolor may be distinct from lignin and pollutant degradation by P. chrysosporium.