Background: Ethanol has been pointed out as a laccase inducer. However, there are controversial reports about its
efficiencywith some fungi. In this study,we hypothesized that ethanol laccase induced in
Pycnoporus sanguineus
depends on nitrogen nutriment conditions. To prove this,we assessed laccase production in submerged cultures
of
P. sanguineus,with different nitrogen concentrations andwith, orwithout ethanol added in a factorial designed
experiment.
Results: In order to analyze the effects of factors on the response variables, a factorial ANOVA, and
response-surface models were performed. It was found that the nitrogen source was the main factor that
affected laccase production in
P. sanguineus. The treatments with yeast extract (2 g/L) and ethanol (3 g/L)
induced the highest laccase activity (31.01 ± 4.9 U/L), while the treatments with urea reached the lowest
activity (less than 1.6 U/L). Ethanol had positive and synergic effects on laccase production, in accordance with
the surface response model, as long as simple nitrogen sources (urea) were not available.
Conclusions: We suggest that laccase in
P. sanguineus is regulated by a catabolic nitrogen repressionmechanism;
laccase activity is strongly inhibited by urea used as nitrogen source and it decreases when the amount of urea
increases; contrarily, a synergic positive effect was observed between yeast extract and ethanol on laccase
production.
