In this work, supported Cu–Ni bimetallic catalysts were synthesized and evaluated for the in situ hydrogenation and decarboxylation of oleic acid using methanol as a hydrogen donor. The supported Cu–Ni alloy exhibited a significant improvement in both activity and selectivity towards the production of heptadecane in comparison with monometallic Cu and Ni based catalysts. The formation of the Cu–Ni alloy is demonstrated by high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM), energy dispersive X-ray spectroscopy (EDS-mapping), X-ray diffraction (XRD) and temperature programmed reduction (TPR). A partially oxidized Cu in the Cu–Ni alloy is revealed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) following CO adsorption and X-ray photoelectron spectroscopy (XPS). The temperature programmed desorption of ethylene and propane (ethylene/propane-TPD) suggested that the formation of the Cu–Ni alloy inhibited the cracking of C–C bonds compared to Ni, and remarkably increased the selectivity to heptadecane. The temperature programmed desorption of acetic acid (acetic acid-TPD) indicated that the bimetallic Cu–Ni alloy and Ni catalysts had a stronger adsorption of acetic acid than that of the Cu catalyst. The formation of the Cu–Ni alloy and a partially oxidized Cu facilitates the decarboxylation reaction and inhibits the cracking reaction of C–C bonds, leading to enhanced catalytic activity and selectivity.

N-acetyl-d-glucosamine (GlcNAc) possesses many bioactivities that have been used widely in many fields. The enzymatic production of GlcNAc is eco-friendly, with high yields and a mild production process compared with the traditional chemical process. Therefore, it is crucial to discover a better chitinase for GlcNAc production from chitin. A novel chitinase gene (Cmchi1) cloned from Chitinolyticbacter meiyuanensis SYBC-H1 and expressed in Escherichia coli BL21(DE3) cells. The recombinant enzyme (CmChi1) contains a glycosyl hydrolase family 18 catalytic module that shows low identity (12–27%) with the corresponding domain of the well-characterized chitinases. CmChi1 was purified with a recovery yield of 89% by colloidal chitin affinity chromatography, whereupon it had a specific activity of up to 15.3 U/mg. CmChi1 had an approximate molecular mass of 70 kDa after the sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and its optimum activity for colloidal chitin (CC) hydrolysis occurred at pH 5.2 and 50 °C. Furthermore, CmChi1 exhibited kcat/Km values of 7.8 ± 0.11 mL/s/mg and 239.1 ± 2.6 mL/s/μmol toward CC and 4-nitrophenol N,N′-diacetyl-β-d-chitobioside [p-NP-(GlcNAc)2], respectively. Analysis of the hydrolysis products revealed that CmChi1 exhibits exo-acting, endo-acting and N-acetyl-β-d-glucosaminidase activities toward N-acetyl chitooligosaccharides (N-acetyl CHOS) and CC substrates, behavior that makes it different from typical reported chitinases. As a result, GlcNAc could be produced by hydrolyzing CC using recombinant CmChi1 alone with a yield of nearly 100% and separated simply from the hydrolysate with a high purity of 98%. The hydrolytic properties and good environmental adaptions indicate that CmChi1 has excellent potential in commercial GlcNAc production. This is the first report on exo-acting, endo-acting and N-acetyl-β-d-glucosaminidase activities from Chitinolyticbacter species.

In this study, we propose a novel biological fermentation method to process chitin powder utilizing the bacteria Chitinolyticbacter meiyuanensis SYBC-H1. The chitin obtained from this process is called CBF, and it was further investigated for N-acetyl-D-glucosamine (GlcNAc) enzymatic production. This fermentative treatment caused chitin powder to acquire a visible fleecy structure, and scanning electron microscopy showed that the surface of the CBF was a fiber-like structure with a diameter ranging from 10 nm to 200 nm. Moreover, Fourier transform infrared spectrometry, X-ray diffraction and gel permeation chromatography revealed that the crystallinity and average molecular weight of the chitin clearly decreased in the absence of deacetylation following bacterial fermentation treatment. The optimal conditions for bacterial treatment of chitin were determined at 25 °C, 200 rpm, and an initial pH of 7.5 for 12 h. Additionally, 19.2 g L⁻¹ of GlcNAc could be obtained with a yield of 96% from 20 g L⁻¹ of CBF in a batch enzymatic reaction within 6 h. This new approach provided an environmentally friendly and mild method for reducing the crystallinity of chitin and enhancing GlcNAc conversion without the use of oxidants, acids, or other environment unfriendly reagents.