Abstract
Laccases are copper polyphenol oxidases that are interesting for several applications such as in the food industry, sewage treatment and decolorization. The use of agro-industrial byproducts allows bioprocesses development for the production of large quantities at viable cost enzymes. In this study, the laccase production of Agaricus blazei was optimized in submerged cultivation (SmC). First, the following agro-industrial substrates were evaluated: sugarcane molasses, soybean molasses, coffee husks, soybean husks and pellet citrus pulp; and then these nitrogen sources: urea, ammonium sulfate, yeast extract. For the optimization of laccase production, a Plackett-Burman and 2(4-1) incomplete factorial designs were used to evaluate the effect of KH2PO4, MgSO4, KCl, FeSO4, ZnSO4 and the ethanol on laccase activity, and for the optimization of sugarcane molasses, urea, MgSO4 and ethanol concentrations. Finally, laccase production kinetics was determined. The best substrate for laccase production by A. blazei was sugarcane molasses. After optimization, it was found that laccase activity of 9635 U/L was obtained in medium with sugarcane molasses (6 g/L), urea (1.5 g/L), MgSO4 (12 mM), ethanol (1.2 mM ) at 28°C and pH 8.0 during 10 days of cultivation. The results indicate that sugarcane molasses is a promising substrate for A. blazei laccase production. Key words: Agaricus brasiliensis, Agaricus subrufescens, laccase, manganese peroxidase, sugarcane molasses.
Highlights
Laccases are copper containing polyphenol oxidases where copper atoms are distributed among three different highly-conserved binding sites, each one with an important role in the catalytic mechanism of the enzyme (Soden and Dobson, 2001; Couto and Toca-Herrera, 2006)
The sugarcane molasses, soybean molasses and coffee husks increased laccase activity when compared with the control with glucose (Table 1)
The highest (p≤0.05) laccase activity was with sugarcane molasses and it was 1.7, 1.5 and 3.8 times higher than soybean molasses, coffee husk and glucose, respectively
Summary
Laccases are copper containing polyphenol oxidases where copper atoms are distributed among three different highly-conserved binding sites, each one with an important role in the catalytic mechanism of the enzyme (Soden and Dobson, 2001; Couto and Toca-Herrera, 2006). Laccases have different physiological functions such as delignification, defense against oxidative stress produced by lignin degradation and morphogenesis (Giardina et al, 2010). The delignification process by laccase involves the transfer of electrons from phenolic substrates to molecular oxygen, reducing it to water while oxidizing phenolic substrates to semiquinone radicals (Zhou et al, 2013). The number and diversity of substrates susceptible to oxidation by laccase vary greatly from one laccase to another (Dittmer and Kanost, 2010). These peculiarities make it a very interesting enzyme for
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