Discovering and Designing a Chimeric Hyperthermophilic Chitinase for Crystalline Chitin Degradation

Abstract

Chitin is one of the most abundant renewable biopolymers on earth. However, it is highly crystalline and recalcitrant to degrade. Here, we report a hyperthermophilic chitinase (ActChi) to directly hydrolyze crystalline chitin at its optimal temperature of 80 °C. It contains a malectin domain, a fibronectin type-III (Fn3) domain, and a catalytic domain (CD chi ). Both Fn3 and malectin have the function of chitin binding domain (ChBD) to increase the activity. Fn3 also significantly increases thermostability, but malectin decreases it. To enhance both activity and thermostability, we introduced a heterogeneous and hyperthermophilic ChBD at the N-terminus of CD chi to obtain ChBD-CD chi . The activity of this hybrid enzyme is 201 U/μmol for crystalline chitin, which has increased 400% compared with that of ActChi. In addition, ChBD-CD chi can continuously degrade crystalline chitin for more than 4 days at 70 °C to increase the overall hydrolysis rate. The strategy is a good example of green sustainable degradation for crystalline biopolymer in nature.

Hollow dodecahedron K3PW12O40/CdS core-shell S-scheme heterojunction for photocatalytic synergistic H2 evolution and benzyl alcohol oxidation

“…Photocatalytic water splitting has emerged as a sustainable, green method for H2 generation [9][10][11][12]. However, conventional photocatalytic H2 evolution reaction (HER) technologies require sacrificial agents to enhance photogenerated carrier separation, posing challenges for practical application (Scheme 1) [13][14][15][16]. By employing a suitable sacrificial agent that participates in a value-added reaction, it is feasible to co-produce H2 fuel and high-value-added products using light as the sole energy input [17][18][19].…”