The α-amino acid ester acyltransferase (SAET) from Sphingobacterium siyangensis is one of the enzymes with the highest catalytic ability for the biosynthesis of l-alanyl-l-glutamine (Ala-Gln) with unprotected l-alanine methylester and l-glutamine. To improve the catalytic performance of SAET, a one-step method was used to rapidly prepare the immobilized cells (SAET@ZIF-8) in the aqueous system. The engineered Escherichia coli (E. coli) expressing SAET was encapsulated into the imidazole framework structure of metal organic zeolite (ZIF-8). Subsequently, the obtained SAET@ZIF-8 was characterized, and the catalytic activity, reusability and storage stability were also investigated. Results showed that the morphology of the prepared SAET@ZIF-8 nanoparticles was basically the same as that of the standard ZIF-8 materials reported in literature, and the introduction of cells did not significantly change the morphology of ZIF-8. After repeated use for 7 times, SAET@ZIF-8 could still retain 67% of the initial catalytic activity. Maintained at room temperature for 4 days, 50% of the original catalytic activity of SAET@ZIF-8 could be retained, indicating that SAET@ZIF-8 has good stability for reuse and storage. When used in the biosynthesis of Ala-Gln, the final concentration of Ala-Gln reached 62.83 mmol/L (13.65 g/L) after 30 min, the yield reached 0.455 g/(L·min), and the conversion rate relative to glutamine was 62.83%. All these results suggested that the preparation of SAET@ZIF-8 is an efficient strategy for the biosynthesis of Ala-Gln.
Escherichia coli/genetics* ; Glutamine ; Zeolites/chemistry* ; Amino Acids

The effects of reaction temperature, ethanol concentration and weight hourly space velocity (WHSV) on the ethylene production from ethanol dehydration using zinc, manganese and cobalt modified HZSM-5 catalyst were investigated by response surface methodology (RSM). The results showed that the most significant effect among factors was reaction temperature and the factors had interaction. The optimum conditions were found as 34.4% ethanol concentration, 261.3 0 degrees C of reaction temperature and 1.18 h(-1) of WHSV, under these conditions the yield of ethylene achieved 98.69%.
Catalysis ; Cobalt ; chemistry ; Dehydration ; Ethanol ; chemistry ; Ethylenes ; chemistry ; metabolism ; Manganese ; chemistry ; Zeolites ; chemistry ; Zinc ; chemistry

Pyrolysis of cellulose with different catalysts has been conducted in a fixed-bed reactor. Micro-mesoporous composite molecular sieves of ZSM-5(38)/A1-MCM-41 with different Si/A1 ratios were prepared under hydrothermal conditions. With powder X-ray diffraction (XRD), the catalyst samples were characterized. GC-MS was used to analyze the bio-oil composition. The effects of catalysts on the pyrolysis product yields were investigated and the results were compared with the results of experiments performed without catalyst under the same pyrolitic conditions. The presence of the catalysts decreased the liquid yield, while increased the moisture content. The major improvement in the quality of bio-oil with the use of catalysts was the increase of DL-2,3-Butanediol. ZSM-5(38)/A1-MCM-41(20) favored the formation of phenol and 2-methoxy-phenol. In addition, these catalysts were all benefit for the generation of small molecular compounds. Also, it was found that ZSM-5(38) was better for the production of C4-C5 compounds. And micro-mesoporous composite molecular sieves mainly promoted the production of C6-C8 compounds.
Catalysis ; Cellulose ; metabolism ; Plant Oils ; metabolism ; Refuse Disposal ; Silicon Dioxide ; chemistry ; Zeolites ; chemistry

The treatment of bleeding wound of solid visceral and the rescue of uncontrollable bleeding are still confronted with difficulties in surgery and first-aid field. Many researchers devote to study in the field of hemostasis, and the novel porous hemostatic agent is one of the hot spot of research about hemostasis. The review focuses on the hemostatic effect, properties, hemostatic mechanism, shortcoming and future trends of three novel porous hemostatic agents such as polysaccharides, zeolite and wollastonite.
Calcium Compounds ; Hemorrhage ; therapy ; Hemostatic Techniques ; Hemostatics ; administration & dosage ; chemistry ; Humans ; Polysaccharides ; Porosity ; Silicates ; Zeolites