Enzyme-Powered Nanomotor as a Mobile Immobilization Carrier for Facilitating the Enzymatic Degradation of Chitin.

Abstract

Chitin, the second most abundant biomass after cellulose on earth, can be degraded into chitin oligosaccharides (CHOS), which hold considerable commercial value. However, the sustainable bioconversion of chitin is impeded by its mass transfer limitations and poor accessibility of chitinase to the substrate. Herein, a Janus urease-powered nanomotor (JUNM) was synthesized via a facile approach and employed as an immobilization carrier for chitinase (Chi B) to improve the enzymatic production of CHOS. It was demonstrated that the structural asymmetry of JUNM enabled the asymmetric decomposition of urea, thereby achieving more efficient self-propulsion at low urea concentrations than a symmetric urease-powered nanomotor (UNM). The self-propulsive behavior of the resulting immobilized chitinase nanomotor (Chi B@JUNM) enhanced its enzymatic performance. Compared with the passive counterpart, the enhanced enzyme-substrate contact induced by the autonomous movement and by the substrate adsorption resulting from electrostatic interactions improved the substrate affinity (a 50% decrease in apparent Km) and led to a 53% increase in catalytic efficiency (apparent kcat·Km-1). Moreover, the immobilization of Chi B on JUNM exhibited typical advantages of enhanced stability and reusability. As a result, the final CHOS yield achieved by the self-propelled Chi B@JUNM (with 50 mM urea) was 1.34 and 2.15 times the yield of passive Chi B@JUNM and free Chi B, respectively. Taken together, the reported enzyme-powered nanomotor provided an efficient platform for chitin degradation and paved the way for the design of advanced immobilization carriers to facilitate enzymatic reactions.

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