Characterization of Aspergillus fumigatus CAS-21 tannase with potential for propyl gallate synthesis and treatment of tannery effluent from leather industry
2018
Cavalcanti, RayzaMorganna Farias | Jorge, JoãoAtílio | Guimarães, LuisHenrique Souza
One of the tannase isoforms produced by the fungus Aspergillus fumigatus CAS-21 under submerged fermentation (SbmF) was purified 4.9-fold with a 10.2% recovery. The glycoprotein (39.1% carbohydrate content) showed an estimated molecular mass of 60 kDa. Optimum temperature and pH for its activity were 30–40 °C and 5.0, respectively. It showed a half-life (t₅₀) of 60 min at 45 and 50 °C, and it was stable at pH 5.0 and 6.0 for 3 h. The tannase activity was insensitive to most salts used, but it reduced in the presence of Fe₂(SO₄)₃ and FeCl₃. On contrary, in presence of SDS, Triton-X100, and urea the enzyme activity increased. The Kₘ value indicated high affinity for propyl gallate (3.61 mmol L⁻¹) when compared with tannic acid (6.38 mmol L⁻¹) and methyl gallate (6.28 mmol L⁻¹), but the best Kcₐₜ (362.24 s⁻¹) and Kcₐₜ/Kₘ (56.78 s⁻¹ mmol⁻¹ L) were obtained for tannic acid. The purified tannase reduced 89 and 25% of tannin content of the leather tannery effluent generated by manual and mechanical processing, respectively, after 2-h treatment. The total phenolic content was also reduced. Additionally, the enzyme produced propyl gallate, indicating its ability to do the transesterification reaction. Thus, A. fumigatus CAS-21 tannase presents interesting properties, especially the ability to degrade tannery effluent, highlighting its potential in biotechnological applications.
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