Ethanol induction of laccase depends on nitrogen conditions of Pycnoporus sanguineus

Christian A Hernández,Julieta Mallerman,Enrique Alarcón,Isabelle Perraud-Gaime,Norma Sandoval,Anne-Marie Farnet,José Antonio García-Pérez

doi:10.1016/j.ejbt.2015.05.008

Abstract

article i nfo Background:Ethanol has been pointedout asa laccase inducer.However, thereare controversial reportsabout its efficiency with some fungi. In this study, we hypothesized that ethanol laccase induced inPycnoporus sanguineus depends on nitrogen nutriment conditions. To prove this, we assessed laccase production in submerged cultures of P.sanguineus,withdifferentnitrogenconcentrationsandwith,orwithoutethanoladdedinafactorialdesigned 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 repression mechanism; 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.

Highlights

It is well known that nitrogen is one of the main nutrients for microbial metabolism because it is an essential component of proteins and nucleic acids, as well as carbon
In all treatments with urea as nitrogen supply (Fig. 1b) laccase activity was lower than 1.6 U/L
In accordance with previous reports for other fungi [3] such as P. ostreatus, our ANOVA results indicate that the source of nitrogen is the most significant source of variation in laccase activity, and that the yeast extract promotes more laccase production in a submerged culture than urea

Summary

Introduction

It is well known that nitrogen is one of the main nutrients for microbial metabolism because it is an essential component of proteins and nucleic acids, as well as carbon. Thereby, it has been observed that laccase production in submerged cultures is performed in the presence of nitrogen as a simple mineral source (such as ammonium nitrate and ammonium sulfate [11]), or complex organic supplies (e.g. a mixture of amino acids, peptone, and yeast extract, [12,13,14]). In this sense, high laccase yields have been reported, when complex organic nitrogen was added to the medium, in contrast with a simple mineral nitrogen source, for Agaricus bisporius [15], Pleurotus ostreatus [3], Trametes hirsuta [16] and Trametes pubescens [17]. Conclusions: We suggest that laccase in P. sanguineus is regulated by a catabolic nitrogen repression mechanism; 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

Methods

Results

Discussion

Conclusion