Impact of nitrogen concentration on validamycin A production and related gene transcription in fermentation of Streptomyces hygroscopicus 5008

State Key Laboratory of Bioreactor Engineering, School of Biotechnology, East China University of Science and Technology, Shanghai, China,
Bioprocess and Biosystems Engineering (Impact Factor: 2). 03/2012; 35(7):1201-8. DOI: 10.1007/s00449-012-0707-3
Source: PubMed


Validamycin A (VAL-A) is an important and widely used agricultural antibiotic. In this study, statistical screening designs were applied to identify significant medium variables for VAL-A production and to find their optimal levels. The optimized medium caused 70% enhancement of VAL-A production. The difference between optimized medium and original medium suggested that low nitrogen source level might attribute to the enhancement of VAL-A production. The addition of different nitrogen sources to the optimized medium inhibited VAL-A production, which confirmed the importance of nitrogen concentration for VAL-A production. Furthermore, differences in structural gene transcription and enzyme activity between the two media were assayed. The results showed that lower nitrogen level in the optimized medium could regulate VAL-A production in gene transcriptional level. Our previous study indicated that the transcription of VAL-A structural genes could be enhanced at elevated temperature. In this work, the increased fermentation temperature from 37 to 42 °C with the optimized medium enhanced VAL-A production by 39%, which testified to the importance of structural gene transcription in VAL-A production. The information is useful for further VAL-A production enhancement.

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Available from: Jian-Jiang Zhong, May 17, 2015
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    • "3.1. Effect of initial corncob hydrolysate concentration on VAL-A production In general, a relatively high sugar concentration may lead to a higher VAL-A titer in its fermentation (Wei et al., 2012). To investigate the feasibility of using corncob hydrolysate as a low-cost raw material by S. hygroscopicus 5008, various initial concentrations of corncob hydrolysate were attempted for VAL-A fermentation. "
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    ABSTRACT: Validamycin A (VAL-A) is an important agricultural antibiotic produced by Streptomyces hygroscopicus 5008, which uses starch as carbon source occupying about 20% of total production cost. To reduce the medium cost, corncob hydrolysate – a hemicellulose hydrolysate was applied as a low-cost substrate to VAL-A fermentation. It was found that three major sugars in corncob hydrolysate including d-glucose, d-xylose and l-arabinose could all be utilized by S. hygroscopicus 5008 to produce VAL-A while d-xylose was the main contributor. A higher VAL-A production titer from d-xylose was achieved by using a genetically engineered strain TC03 derived from S. hygroscopicus 5008, which resulted in 1.27-fold improvement of VAL-A production from the medium containing 13% (v/v) corncob hydrolysate compared to that by its original strain. A medium cost analysis was done and compared with previous reports. This work indicates a great potential of the hemicellulose hydrolysate as substrate for antibiotic fermentation.
    Bioresource Technology 01/2015; 175. DOI:10.1016/j.biortech.2014.10.051 · 4.49 Impact Factor
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    • "Due to a large market for VAL-A, a great deal of research and development has been undertaken to improve its production titer and to reduce its production cost as low as possible. These investigations range from process improvement such as medium optimization with agro-industrial residues (Wei et al. 2012a), application of fermentation strategies (Wei et al. 2012b), and stimulator addition (Tan et al. 2013; Wei et al. 2011; Zhou et al. 2012), to metabolic pathways for increasing precursor supply (Zhou et al. 2011). For industrial scale production , strain improvement is essential to obtain a relatively high amount of products. "
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    ABSTRACT: Validamycin A (VAL-A) is a widely used antifungal antibiotic for the treatment of sheath blight disease of rice and other plants. It can be produced from agro-industrial by-products by Streptomyces hygroscopicus 5008. To enhance its production titer, in this work, the entire val gene cluster was amplified in tandem in S. hygroscopicus 5008 by integrating the zouA-mediated DNA amplification system into between the two boundaries of val gene cluster, resulting in multiple copies (mainly three to five) of the val gene cluster. The genetic stability of the amplified copies was confirmed by Southern blot and fermentation experiments. In shake flask fermentation, the recombinant strain (TC03) led to a 34 % enhancement of VAL-A production titer compared to that of the wild-type strain, while the accumulation of intermediate validoxylamine A was decreased in TC03. Additionally, both the structural gene transcription levels and the ValG enzyme activity were significantly increased in TC03. This work demonstrated that the amplification of the val gene cluster was an efficient strategy to enhance VAL-A production by S. hygroscopicus 5008, and the information obtained would be helpful for engineering other interesting antibiotic biosynthesis by gene cluster amplification.
    Applied Microbiology and Biotechnology 07/2014; 98(18). DOI:10.1007/s00253-014-5943-9 · 3.34 Impact Factor
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    ABSTRACT: Sodium decanoate was first found to be an effective precursor for synthesis of daptomycin from Streptomyces roseosporus NRRL11379 which was increased to 71.55-fold, compared with decanoic acid. The optimal flow rate of precursor was at 600 mg/(L day) after 48 h fermentation. From protein analysis via SDS-PAGE and identification of Tandem MS/MS afterwards, it deciphered that guanosine pentaphosphate synthetase, PNPase, tripeptidylamino peptidase primarily dealing with daptomycin synthesis. By applying Taguchi's L16 in culture optimization, the best yield was obtained from the medium with 60 g/L dextrin, 10 g/L dextrose, 1.0 g/L molasses, and 8 g/L yeast extract, respectively. The fed-batch fermentation, applied with feedback control of dextrin, stimulated the production up to 812 mg/L at 288 h. To our best knowledge, the daptomycin production in this study is significantly higher than that in previous studies and can make it more widely used in pharmaceutical industry.
    Bioprocess and Biosystems Engineering 07/2013; 37(3). DOI:10.1007/s00449-013-1007-2 · 2.00 Impact Factor
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