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Wu J.,Nanjing University of Technology | Wu J.,National Engineering Technique Research Center for Biotechnology | Chen C.,Research Institute of Benzene Chemical
Acta Crystallographica Section E: Structure Reports Online | Year: 2014

In the title compound, C21H26O2SSe, the S atom adopts a pyramidal geometry (bond-angle sum = 304°) and the n-butyl chain shows an extended conformation. An intramolecular C-H⋯O hydrogen bond closes an S(8) ring. In the crystal, inversion dimers are formed with molecules linked by pairs of O-H⋯O=S hydrogen bonds, generating R 2 2(14) loops. Weak C-H⋯O interactions also occur. Source


Li H.,Nanjing University of Technology | Xu H.,Nanjing University of Technology | Li S.,Nanjing University of Technology | Guo C.,Nanjing University of Technology | And 3 more authors.
Biotechnology and Bioprocess Engineering | Year: 2010

Low-energy nitrogen ion beam implantation technique was used for the strain improvement of Alcaligenes sp. NX-3 for the production of exopolysaccharide welan gum. A high welan gum producing mutant, Alcaligenes sp. NX-3-1, was obtained through 20 keV N + ion beam irradiation. Starting at a concentration of 50 g/L of glucose, mutant NX-3-1 produced 25.0 g/L of welan gum after 66 h of cultivation in a 7.5 L bioreactor, which was 34.4% higher than that produced by the wild-type strain. The results of metabolic flux analysis showed that the glucose-6-phosphate and acetyl coenzyme A nodes were the principle and flexible nodes, respectively. At the glucose-6-phosphate node, the fraction of carbon measured from glucose-6-phosphate to glucose-1-phosphate was enhanced after mutagenesis, which indicated that more flux was used to synthesize welan gum in the mutant. By analyzing the activities of related enzymes in the biosynthetic pathway of sugar nucleotides essential for welan gum production, we found that the specific activities of phosphoglucomutase, UDP-glucose pyrophosphorylase, UDP-glucose dehydrogenase, and dTDP-glucose pyrophosphorylase in the mutant strain were higher than those in the wild-type strain. These improvements in enzyme activities could be due to the affected of ion beam implantation. © 2010 The Korean Society for Biotechnology and Bioengineering and Springer-Verlag Berlin Heidelberg. Source


Ren B.,Nanjing University of Technology | Li S.,Nanjing University of Technology | Xu H.,Nanjing University of Technology | Feng X.-H.,Nanjing University of Technology | And 2 more authors.
Bioprocess and Biosystems Engineering | Year: 2011

A highly selective sucrose isomerase (SIase) was purified to homogeneity from the cell-free extract of Erwinia rhapontici NX-5 with a recovery of 27.7% and a fold purification of 213.6. The purified SIase showed a high specific activity of 427.1 U mg-1 with molecular weight of 65.6 kDa. The K m for sucrose was 222 mM while V max was 546 U mg -1. The optimum pH and temperature for SIase activity were 6.0 and 30 °C, respectively. The purified SIase was stable in the temperature range of 10-40 °C and retained 65% of the enzyme activity after 2 weeks' storage at 30 °C. The SIase activity was enhanced by Mg2+ and Mn 2+, inhibited by Ca2+, Cu2+, Zn2+, and Co2+, completely inhibited by Hg2+ and Ag 2+. The purified SIase was strongly inhibited by SDS, while partially inhibited by dimethylformamide, tetrahydrofuran, and PMSF. Additionally, glucose and fructose acted as competitive inhibitors for purified SIase. © 2011 Springer-Verlag. Source


Ji W.,State Key Laboratory of Materials Oriented Chemical Engineering | Ji W.,Nanjing University of Technology | Ji W.,National Engineering Technique Research Center for Biotechnology | Sun W.,University of North Carolina at Chapel Hill | And 10 more authors.
Scientific Reports | Year: 2015

N-Acetylneuraminic acid lyase (NAL, E.C. number 4.1.3.3) is a Class I aldolase that catalyzes the reversible aldol cleavage of N-acetylneuraminic acid (Neu5Ac) from pyruvate and N-acetyl-D-mannosamine (ManNAc). Due to the equilibrium favoring Neu5Ac cleavage, the enzyme catalyzes the rate-limiting step of two biocatalytic reactions producing Neu5Ac in industry. We report the biochemical characterization of a novel NAL from a "GRAS" (General recognized as safe) strain C. glutamicum ATCC 13032 (CgNal). Compared to all previously reported NALs, CgNal exhibited the lowest kcat/Km value for Neu5Ac and highest kcat/Km values for ManNAc and pyruvate, which makes CgNal favor Neu5Ac synthesis the most. The recombinant CgNal reached the highest expression level (480 mg/L culture), and the highest reported yield of Neu5Ac was achieved (194 g/L, 0.63 M). All these unique properties make CgNal a promising biocatalyst for industrial Neu5Ac biosynthesis. Additionally, although showing the best Neu5Ac synthesis activity among the NAL family, CgNal is more related to dihydrodipicolinate synthase (DHDPS) by phylogenetic analysis. The activities of CgNal towards both NAL's and DHDPS' substrates are fairly high, which indicates CgNal a bi-functional enzyme. The sequence analysis suggests that CgNal might have adopted a unique set of residues for substrates recognition. Source


Ye Q.,State Key Laboratory of Materials Oriented Chemical Engineering | Ye Q.,Nanjing University of Technology | Ye Q.,National Engineering Technique Research Center for Biotechnology | Ouyang P.,State Key Laboratory of Materials Oriented Chemical Engineering | And 5 more authors.
Applied Microbiology and Biotechnology | Year: 2011

Ethyl (S)-4-chloro-3-hydroxybutanoate ester ((S)-CHBE) is a precursor of enantiopure intermediates used for the production of chiral drugs, including the cholesterol-lowering 3-hydroxy-3-methyl-glutaryl CoA reductase inhibitors (statins). The asymmetric reduction of ethyl 4-chloro-3-oxobutanoate ester (COBE) to (S)-CHBE by biocatalysis has several positive attributes, including low cost, mild reaction conditions, high yield, and a high level of enantioselectivity. During genome database mining of the yeast Pichia stipitis, our group found two novel carbonyl reductases (PsCRI and PsCRII) that have a promising future for the industrial production of (S)-CHBE with >99% enantiomeric excess. This review covers the main process of biosynthesis of (S)-CHBE: screening of microorganisms that catalyze the reduction of COBE to (S)-CHBE (I); gene cloning, expression, and characterization of carbonyl reductases for the production of (S)-CHBE in Escherichia coli (II); development of cofactor generation systems for regenerating cofactors (III); and biocatalysis of COBE to (S)-CHBE by recombinant E. coli (IV). © 2010 Springer-Verlag. Source

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