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ABSTRACT: Nucleoside analogues are used widely for the treatment of viral diseases and cancer, however the preparation of some important intermediates of these nucleoside analogues, including 2'-deoxyadenosine (dAR) and 5-methyluridine (5-MU), remains inconvenient. To optimize the synthesis of dAR and 5-MU, recombinant strains and auto-induction medium were employed in this study. E. coli BL21(DE3) strains overexpressing purine nucleoside phosphorylase (PNP), uridine phosphorylase (UP) and thymidine phosphorylase (TP) were constructed and cultured in auto-induction ZYM-Fe-5052 medium for 8 h. The cultures of these strains were then used directly to synthesize dAR and 5-MU. Under optimized conditions, 30 mM adenine was converted to 29 mM dAR in 1 h, and 32 mM 5-MU was obtained from 60 mM thymine, using 6% (v/v) cell solutions as biocatalysts. These results indicate that our convenient and efficient method is ideal for the preparation of dAR and 5-MU, and has potential for the preparation of other nucleoside analogue intermediates.
MIRCEN Journal of Applied Microbiology and Biotechnology 02/2012; 28(2):721-7. · 1.08 Impact Factor
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ABSTRACT: N-deoxyribosyltransferases are essential enzymes in the nucleotide salvage pathway of lactobacilli. They catalyze the exchange between the purine or pyrimidine bases of 2'-deoxyribonucleosides and free pyrimidine or purine bases. In general, N-deoxyribosyltransferases are referred to as cytoplasmic enzymes, although there is no experimental evidence for this subcellular localization. In this work, the subcellular localization of N-deoxyribosyltransferase II (NTD) from Lactobacillus fermentum was examined by subcellular fractionation, transmission electron microscopy, and fluorescence microscopy. Our results indicate that L. fermentum NTD are distributed not only in the cytoplasm but also on the cell wall surface, and further studies showed that surface-attached NTD can be released into the culture broth and conventional buffers.
FEMS Microbiology Letters 10/2011; 323(2):132-41. · 2.04 Impact Factor
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ABSTRACT: Prednisolone represents an important compound in pharmaceutical preparations. To obtain more bioactive prednisolone derivatives, the microbial transformation of prednisolone was carried out. The steroid products were assigned by an interpretation of their spectral data using mass spectrometry and proton nuclear magnetic resonance ((1)H NMR) analyses. The product was assigned the chemical structure of 11β, 17α, 20β, 21-tetrahydroxypregna-1,4-diene-3-one (named as 20β-hydroxy prednisolone). The conversion of prednisolone to 20β-hydroxy prednisolone by Streptomyces roseochromogenes TS79 was different from a previous study on the microbial transformation of steroid by this organism, which usually generates a 16α-hydroxy steroid product. The different reaction parameters for maximum conversion of prednisolone were optimized. The analysis revealed that the optimum values of the tested variables were 7.5 mg/ml prednisolone dissolved in DMSO and added to the 24-h pre-culture fermentation culture containing 0.05% MgSO(4) and incubated for 24 h. A conversion of 95.1% of prednisolone was observed, which has the potential to be used in industrial production.
Applied Microbiology and Biotechnology 06/2011; 92(4):727-35. · 3.42 Impact Factor
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ABSTRACT: Mutant libraries of avermectin-producing Streptomyces avermitilis strains were constructed by different mutagenesis strategies. A metric was applied to assess the mutation spectrum by calculating the distribution of average phenotypic distance of each population. The results showed for the first time that a microgravity environment could introduce larger phenotype distribution and diversity than UV and N-methyl-N-nitro-N-nitrosoguanidine (NTG) could.
Applied and environmental microbiology 07/2010; 76(13):4583-6. · 3.69 Impact Factor
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Ying Zhuo, Wenquan Zhang,
Difei Chen,
Hong Gao,
Jun Tao,
Mei Liu,
Zhongxuan Gou,
Xianlong Zhou,
Bang-Ce Ye,
Qing Zhang,
Siliang Zhang,
Li-Xin Zhang
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ABSTRACT: Avermectin and its analogues are produced by the actinomycete Streptomyces avermitilis and are widely used in the field of animal health, agriculture, and human health. Here we have adopted a practical approach to successfully improve avermectin production in an industrial overproducer. Transcriptional levels of the wild-type strain and industrial overproducer in production cultures were monitored using microarray analysis. The avermectin biosynthetic genes, especially the pathway-specific regulatory gene, aveR, were up-regulated in the high-producing strain. The upstream promoter region of aveR was predicted and proved to be directly recognized by sigma(hrdB) in vitro. A mutant library of hrdB gene was constructed by error-prone PCR and selected by high-throughput screening. As a result of evolved hrdB expressed in the modified avermectin high-producing strain, 6.38 g/L of avermectin B1a was produced with over 50% yield improvement, in which the transcription level of aveR was significantly increased. The relevant residues were identified to center in the conserved regions. Engineering of the hrdB gene can not only elicit the overexpression of aveR but also allows for simultaneous transcription of many other genes. The results indicate that manipulating the key genes revealed by reverse engineering can effectively improve the yield of the target metabolites, providing a route to optimize production in these complex regulatory systems.
Proceedings of the National Academy of Sciences 06/2010; 107(25):11250-4. · 9.68 Impact Factor
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Hong Gao,
Mei Liu,
Xianlong Zhou,
Jintao Liu,
Ying Zhuo,
Zhongxuan Gou,
Bing Xu, Wenquan Zhang,
Xiangyang Liu,
Aiqun Luo,
Chuansen Zheng,
Xiaoping Chen,
Lixin Zhang
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ABSTRACT: Avermectins produced by Streptomyces avermitilis are potent against a broad spectrum of nematode and arthropod parasites with low-level side effects on the host organisms. This study was designed to investigate a high-throughput screening strategy for the efficient identification of avermectin high-yield strains. The production protocol was miniaturized in 96 deep-well microplates. UV absorbance at 245 nm was used to monitor avermectin production. A good correlation between fermentation results in both 96 deep-well microplates and conventional Erlenmeyer flasks was observed. With this protocol, the production of avermectins was determined in less than 10 min for a full plate without compromising accuracy. The high-yield strain selected through this protocol was also tested in 360 m(3) batch fermentation with 1.6-fold improved outcome. Thus, the development of this protocol is expected to accelerate the selection of superior avermectin-producing strains.
Applied Microbiology and Biotechnology 12/2009; 85(4):1219-25. · 3.42 Impact Factor
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ABSTRACT: Response surface methodology was employed to optimize the composition of medium for the production of avermectin B1a by Streptomyces avermitilis 14-12A in shaker flask cultivation. Corn starch and yeast extract were found to have significant effects on avermectin B1a production by the Plackett-Burman design. The steepest ascent method was used to access the optimal region of the medium composition, followed by an application of response surface. The analysis revealed that the optimum values of the tested variables were 149.57 g/l corn starch and 8.92 g/l yeast extract. A production of 5128 mg/l, which was in agreement with the prediction, was observed in verification experiment. In comparison to the production of original level (3528 mg/l), 1.45-fold increase had been obtained.
Bioresource technology 05/2009; 100(17):4012-6. · 4.25 Impact Factor
