Propane dehydrogenation (PDH) is an industrial technology for direct propylene production which has received extensive attention in recent years. Nevertheless, existing non-oxidative dehydrogenation technologies still suffer from the thermodynamic equilibrium limitations and severe coking. Here, we develop the intensified propane dehydrogenation to propylene by the chemical looping engineering on nanoscale core-shell redox catalysts. The core-shell redox catalyst combines dehydrogenation catalyst and solid oxygen carrier at one particle, preferably compose of two to three atomic layer-type vanadia coating ceria nanodomains. The highest 93.5% propylene selectivity is obtained, sustaining 43.6% propylene yield under 300 long-term dehydrogenation-oxidation cycles, which outperforms an analog of industrially relevant K-CrO x /Al 2 O 3 catalysts and exhibits 45% energy savings in the scale-up of chemical looping scheme. Combining in situ spectroscopies, kinetics, and theoretical calculation, an intrinsically dynamic lattice oxygen “donator-acceptor” process is proposed that O 2- generated from the ceria oxygen carrier is boosted to diffuse and transfer to vanadia dehydrogenation sites via a concerted hopping pathway at the interface, stabilizing surface vanadia with moderate oxygen coverage at pseudo steady state for selective dehydrogenation without significant overoxidation or cracking.
Bin Ma,Jiafeng Niu,Hao Zhu,Huibing Chi,Zhaoxin Lu,Fengxia Lu,Ping Zhu
Aldo-keto reductase is responsible for the formation of nontoxic 3-epi-deoxynivalenol (3-epi-DON) from 3-keto-DON, which is an enzymatic detoxification manner to completely eliminate the toxicity of mycotoxin DON against health and environmental threats. Therefore, unlocking the facilitated substrate specificity of aldo-keto reductase for 3-keto-DON has become a critical challenge for advanced catalytic performance. In this endeavor, a loop-based engineering strategy was developed for aldo-keto reductase AKR13B3 from Devosia A6–243 to catalyze 3-keto-DON. A 31.9-fold switch from a disfavored substrate to the preferred one was produced along with a significant 37.9-fold increase in catalytic efficiency. Kinetic parameter determinations, structural analyses, and molecular simulations were employed to elucidate the molecular mechanisms underlying these enhancements in catalytic activity and substrate specificity. Overall, our work presents a feasible scheme for designing aldo-keto reductases with exceptional substrate specificity and catalytic activity, holding great promise for developing enzymatic detoxification agents.
Kemin Lv,Xiaozhou Li,Kequan Chen,Bin Wu,Bingfang He,Gerhard Schenk
Processive endoglucanase is a typical bifunctional biocatalyst for cellulose degradation. A GH5 processive endoglucanase from Bacillus subtilis BS-5 was previously identified and shown to exhibit highly efficient catalytic performance. To further augment its catalytic efficiency, both consensus mutagenesis and loop engineering were applied. Compared to the wild-type enzyme, a variant (M3-1) with the four point mutations, i.e., K91I, A198T, Q237D, and V240P, exhibits an 8.5- and 4.8-fold increase in catalytic efficiency toward the soluble substrate carboxymethyl cellulose-Na (CMC) and the insoluble phosphoric acid-swollen cellulose (PASC), respectively. Molecular dynamics simulations were employed to elucidate the conformational changes that led to the enhanced catalytic efficiency. Structural superpositions suggest that the mutations cause a swing in loop 230–241, which in turn affects enzyme–substrate affinity and recognition. Residues K91 and A198 are located distal from the active site. The mutations K91I and A198T influence key amino acids within the active pocket through residue interaction networks in the protein. Furthermore, dynamic cross-correlation matrices (DCCMs) indicate that variant M3-1 possesses a conformation that is more favorable than that of the wild-type enzyme, promoting an increased frequency of interactions between active site residues and substrate molecules and thereby enhancing catalytic efficiency. The combined results provide valuable insights into the rational design and engineering of processive endoglucanases and other glycoside hydrolases, enabling the development of improved enzymatic catalysts for biotechnology applications.
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