Improving laccase thermostability with aqueous natural deep eutectic solvents.

The wide-spread use of laccases in industry is often limited due to the enzyme inactivation over time at conditions which exceeds the operating conditions of the enzymes, which are neutral pH and ambient temperatures (30-40 °C). Natural Deep Eutectic Solvents (NADESs) have attracted considerable attention as reaction media in biocatalysis due to their promising compatibility with enzymes and sustainable derivation. In this contribution we demonstrate the possibility of applying aqueous NADESs as incubation media to alter the activity of and inhibit thermal inactivation of laccase T. versicolor. For example we show that by incubating 0.25 g L-1 laccase in an aqueous 25 wt% betaine-xylitol based NADES at 70 °C for 15 min, the measured residual activity of laccase is a near 10 fold greater than the measured residual activity of laccase when incubated without the NADES. Moreover, the comparison of the residual activities of the enzyme in presence betaine, xylitol or NADES is clearly showing the advantage of using a NADES because a synergistic effect. The drastic enhancement of the enzyme thermostability by pre-incubation of laccase in NADES media showcases a facile, cheap and green method of boosting the stability laccase.