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Ulvan lyase degrades the ulvan from green macroalgae, which is a very attractive biocatalyst in algae biomass degradation. Here, a novel N57P mutant from Nonlabens ulvanivorans ulvan lyase (NuPL28) with improved catalytic efficiency and thermostability was rationally designed. Compared with the wild type, the kinetic parameters (k cat and k cat /K m ) of N57P were 2.46 and 3.20 times higher than that of WT, respectively. The N57P variant cooperating with commercial cellulase showed 1.33-fold higher activity for degradation of ulva powder to unsaturated sugar than that of WT. Molecular dynamics (MD) simulations were performed to reveal that the N57P mutant anchored the substrate in the active site through reducing the flexibility of the two loops T102-R117 and G209-R216. Moreover, it is also found that, compared with WT, the catalytic residues of N57P possessed a suitable nucleophilic attack distance and more hydrogen bonds with the tetrasaccharide. These findings would facilitate the discovery of the improved catalytic behavior of ulvan lyase and reduce the cost of algal biomass conversion.

Saponin is an important class of natural products with various pharmacological activities. The selective separation of saponins is an essential step before further analysis.Molecular imprinting has been an effective strategy for preparing antibody mimics. However, a facile and efficient imprinting strategy for saponins is still lacking owing to their amphiphilic nature. Herein, we have prepared the saponins imprinted nanoparticles via cooperative imprinting strategy. This new strategy relies on the combination of various non-covalent interactions (hydrophobic and hydrogen bonding) and covalent boronate affinity interactions. The obtained imprinted nanoparticles could rebind specific saponins from complex matrices with good selectivity, superb tolerance to interference, and fast binding equilibrium. This method was verified to be versatile and facile. Thus, this strategy could greatly facilitate the preparation of imprinted nanoparticles for the specific recognition of saponins. K E Y W O R D Samphiphilic molecules, mass spectrometry, molecular imprinting, sample preparation, saponins 2162