Enhanced production of cytidine 5'-monophosphate using biocatalysis of di-enzymes immobilized on amino-functionalized sepharose

Cytidine 5'-monophosphate(5'-CMP)is an essential nucleotide for additives.In this study,enhanced production of 5'-CMP was realized by the transformation of cytidine using co-immobilized di-enzymes,uridine-cytidine kinase(UCK)and acetate kinase(AcK).The immobilization yield of the enzyme had a clear correlation with the surface charges as zeta potential(ξ).Among them,ε-polylysinefunctionalized sepharose(SA-EPL,ξ=9.31 m V)showed high immobilization yield(78.8%),which was4.9-fold than that of nitrilotriacetic acid functionalized sepharose(SA-NTA,ξ=-12.6 m V).The residual activity of affinity co-immobilized enzyme(EPL-Ni/EPL@Ac K-UCK)was higher than 70.6%after recycled 10 times.Thus,this study provides an effective approach for the production of 5'-CMP with the advantages of low adenosine 5'-triphosphate(ATP)consumption,reduced side reactions,and improved reusability by co-immobilized UCK and Ac K on the functionalized Sepharose.

Rapid Detection of Serum Procalcitonin by Immunochromatograghy Technology Based on Freeze-dried Up-conversion Nanoparticles/Antibody Conjugates

Procalcitonin （PCT） is a sensitive and specific biomarker for sepsis diagnosis and widely used as a biomarker to improve the diagnosis of bacterial infections and to guide the antibiotic therapy. In our work, an improved up-converting nanoparticle （UCP） technology based on the immunochromatographic assay （UPT-ICA） was developed for rapid and quantitative detection of PCT. In order to further improve the accuracy, sensitivity and stability of the assay on the basis of our previous study, the UCP coupling with rnonoclonal antibody of PCT （UCP-Abl） was freeze-dried under certain conditions. And the detections of PCT levels with UCP-Abl conjugates before and after freeze-drying were evaluated. The results show that, compared to the UCP-Abl conjugates without freeze-drying, the detection sensitivity of freeze-dried UCP-Abl is slightly improved, having a lower immunochromatogragh background and better stability. This improved method can provide a rapid, accurate, and relatively easy way for the clinical detection of PCT.

Kinetic studies of xylan hydrolysis of corn stover in a dilute acid cycle spray flow-through reactor

Xylan of corn stover was pretreated with 1%,2%and 3%(w/w)sulfuric acid at relatively low temperatures(90℃,95℃ and 100℃)in a dilute acid cycle sprayflow-through reactor(DCF).The hydrolysis of xylan to its monomeric xylose was modeled by a series offirst-order reactions.Both biphasic and Saeman hydrolysis models were applied tofit the experimental data.The results confirmed that the kinetic data of xylan hydrolysisfitted afirst-order irreversible reaction model and the experimental data.The reaction rates of xylose monomer formation and degradation were sensitive to catalyst concentration and temperature.Higher catalyst concentra-tion and lower reaction temperature result in high xylose yield.The activation energy for xylose formation and degradation were determined to be 112.9 and 101.0 kJ·mol^(-1),respectively.Over 90%theoretical xylose obtained from corn stover can be used to produce ethanol,xylitol and fumaric acid by fermentation.