Glucose and biomass

Glucose concentration was assayed by the method of Luff-Schoorl (19). Biomass was determined as dry weight after drying the samples at 60°C for 48 hours.

RESULTS AND DISCUSSION

T. villosa and P. sanguineus were analyzed regarding their ability to decolorize 28 reactive dyes routinely employed in cotton dyeing (Table 1). T. villosa decolorized all dyes tested, whereas 5 dyes were not decolorized by P. sanguineus. T. villosa completely decolorized 17 dyes, whereas P. sanguineus completely decolorized only 8. Some dyes inhibited fungal growth, with a reduction in the growth rate. In general, dye decolorization progressed more slowly than radial growth and the decolorization halo of some dyes did not occupy the entire diameter of the plate even when the incubation time was prolonged to 21 days. Levafix Orange, Drimaren Brilliant Orange, Drimaren Red and Levafix Red were found to be more resistant to fungal action, probably because of their chemical structure and the presence of chlorine in the molecule (22, 24).

Dye decolorization by fungi during growth on solid medium has been widely employed to identify the ligninolytic potential and potential degradation of xenobiotic compounds by basidiomycetes (13, 23, and 26). The time required by T. villosa and P. sanguineus to decolorize the synthetic dyes was similar to that reported for other basidiomycetes (7 to 20 days).

Differences in the capacity of dye decolorization between fungi have been related to inter- and intra specific variations, the molecular complexity of the dye and culture conditions (6, 15, and 25).The action of T. villosa on a broad spectrum of textile dyes confirms the previously demonstrated biotechnological potential of this fungus (12, 16). P. sanguineus decolorized Drimaren Brilliant Blue, which T. villosa was unable to decolorize completely on solid medium. Therefore, some parameters that Influence the decolorization of dyes by basidiomycetes were studied in submerged culture using this dye and pure and mixed cultures of the two fungi. Shaking favored the decolorization of Drimaren Brilliant Blue by T. villosa (Fig. 1), with about 85% decolorization being obtained after seven days.

Although shaking has been shown to suppress the expression of the ligninolytic system in Phanerochaete chrysosporium (10,26), this condition generally results in higher dye decolorization than obtained with static cultures due to an increase in mass and oxygen transfer between cells and the medium, factors that optimize the action of oxidative enzymes.

However, Kirby et al. (9) observed better dye decolorization by Phlebia tremellosa under static conditions, but decolorization was only determined after 14 days of incubation and therefore monitoring of the decolorization kinetics was not possible.

The initial concentration of the dye influenced the decolorization capacity of T. villosa (Fig. 2).