Tyrosinase from the peels of Musa cavendish: purification, characterization, immobilization and application in phenol biodegradation.

Tyrosinase is an enzyme implicated in fruit ripening and the browning of plant parts exposed to mechanical injury. Tyrosinase has numerous reported biotechnological importance. This enzyme was extracted from the waste peels of Musa cavendish, purified via aqueous two-phase partitioning system (ATPS) and QAE-Sephadex ion-exchange chromatography. The purified tyrosinase was biochemically characterized. Tyrosinase was thereafter immobilized, characterized, and applied in the oxidation of phenols in model wastewaters. After purification, the yield and fold obtained were 23% and 8.0 respectively. The molecular weight of the enzyme was estimated to be 43.0 kDa. The purified enzyme had an optimum pH and temperature of 6.5 and 60 °C respectively. The k cat K m (M−1s−1) obtained for substrates such as L-DOPA, catechol and pyrogallol were 3.6 × 10 4 , 3.8 × 10 4 and 1.6 × 10 4 respectively. The purified enzyme was stable in organic solvents: acetone > ethanol > methanol > n-butanol. Quercetin, ascorbic acid, l-cysteine and arginine were potent inhibitors. The immobilized tyrosinase was more resistant to thermoinactivation than the free enzyme as evidenced by its kinetic ( k d , t 1 / 2 ) and thermodynamic ( Δ G d * , Δ H d * , Δ S d * ) characteristics. The immobilized tyrosinase removed 70% of 650-µM phenol after 2 h compared to 50% removal by the free tyrosinase. After six repeated cycles of phenol biodegradation using the immobilized enzyme, about 40% of phenol was removed. The fresh peels of M. cavendish served as a green-based source of relatively thermostable immobilized tyrosinase deployable in large-scale biodegradation of phenol-containing wastewater. [ABSTRACT FROM AUTHOR]