Integrated strategy for purification of esterase from Aureobasidium pullulans

Abstract

Esterases catalyze the cleavage and formation of ester bonds of a broad range of substrates presenting a widespread spectrum of industrial applications. This work aimed to partially purify and characterize an esterase from Aureobasidium pullulans LABIOTEC 01 produced in a culture medium containing olive mill wastewater. Esterase purification was evaluated using different strategies, namely the enzyme recovery by PEG-salt aqueous two-phase systems (ATPSs); and the enzyme precipitation with ammonium sulfate, acetone, and ethanol. The best purification factor (18±2) was obtained when the ATPS composed of 20% (w/w) polyethylene glycol (PEG) 6000 and 5.8% (w/w) potassium phosphate buffer (PPB) pH 8.0 was combined with acetone precipitation. The partially purified enzyme presented an optimum pH of 5.0, although it remained active in the pH range of 4.5 to 7.5 ( 50% relative activity). The optimum temperature was found to be 60°C. Furthermore, the addition of salts such as FeCl3, CuSO4 and MnCl2 promoted an increase in the enzymatic activity (above 100%). The enzyme was found to be stable and showed high activity when exposed to polar solvents such as dimethyl sulfoxide, dimethylformamide, and methanol. The use of an integrated strategy of purification combining simple purification methods such as ATPS and precipitation was herein reported for the first time for esterase. This strategy proved to be an interesting approach to partially purify the esterase produced under submerged fermentation by A. pullulans. Furthermore, the enzyme showed potential to be applied in industrial biocatalytic processes using high temperature and different salts or solvents. Also, the production of esterase using olive mill wastewater as substrate demonstrated to be a suitable alternative to reduce and valorize agro-industrial residues.