Characterization of Aspergillus fumigatus CAS-21 tannase with potential for propyl gallate synthesis and treatment of tannery effluent from leather industry.

Abstract

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 60kDa. Optimum temperature and pH for its activity were 30-40°C and 5.0, respectively. It showed a half-life (t50) of 60min at 45 and 50°C, and it was stable at pH 5.0 and 6.0 for 3h. 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 (3.61mmol L-1) when compared with tannic acid (6.38mmol L-1) and methyl gallate (6.28mmol L-1), but the best Kcat (362.24s-1) and Kcat/Km (56.78s-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.