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Effect of Ammonium in Medium on Ansamitocin P-3 Production by Actinosynnema pretiosum
Jinxia Lin,Linquan Bai,Zixin Deng,Jian-Jiang Zhong 한국생물공학회 2010 Biotechnology and Bioprocess Engineering Vol.15 No.1
Ansamitocin P-3 (AP-3) is an antitumor agent produced by Actinosynnema pretiosum with a market demand for large and cheap supply, but its productivity is yet low. This work investigated the effects of ammonium in medium on the productivity, enzyme activities, and gene transcription for AP-3 biosynthesis. As observed, AP-3 production was depressed by medium ammonium, although the dry cell weight and the consumption of total sugar and isobutanol were not influenced obviously. From the onset of AP-3 accumulation, isobutyrate accumulation showed a different behavior in medium with or without ammonium. Isobutanol dehydrogenase activity was enhanced during production phase in medium with ammonium, but valine dehydrogenase activity was not substantially changed. qRT-PCR analysis revealed that transcriptional levels of structure genes asm14, asm24, asm43, and asm19 were down-regulated by medium ammonium. The transcription of regulatory gene asm2, asm29, and asm31 were slightly up-regulated while that of asm39 was down-regulated by ammonium. The results indicated that inhibition of AP-3 production by ammonium might be related to the AP-3 ester side chain supply and the repression of gene transcription responsible for 3-amino-5-hydroxybenzoic acid and methoxymalonyl-ACP biosynthesis. The information is useful for future AP-3 productivity enhancement.
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Qiong Wu,Linquan Bai,Weicheng Liu,Yingying Li,Caige Lu,Yaqian Li,Kehe Fu,Chuanjin Yu,Jie Chen 한국미생물학회 2013 The journal of microbiology Vol.51 No.2
Streptomyces lydicus A01 and Trichoderma harzianum P1are potential biocontrol agents of fungal diseases in plants. S. lydicus A01 produces natamycin to bind the ergosterol of the fungal cell membrane and inhibits the growth of Botrytis cinerea. T. harzianum P1, on the other hand, features high chitinase activity and decomposes the chitin in the cell wall of B. cinerea. To obtain the synergistic biocontrol effects of chitinase and natamycin on Botrytis cinerea, this study transformed the chit42 gene from T. harzianum P1 to S. lydicus A01. The conjugal transformant (CT) of S. lydicus A01 with the chit42 gene was detected using polymerase chain reaction (PCR). Associated chitinase activity and natamycin production were examined using the 3, 5-dinitrosalicylic acid (DNS)method and ultraviolet spectrophotometry, respectively. The S. lydicus A01-chit42 CT showed substantially higher chitinase activity and natamycin production than its wild type strain (WT). Consequently, the biocontrol effects of S. lydicus A01-chit42 CT on B. cinerea, including inhibition to spore germination and mycelial growth, were highly improved compared with those of the WT. Our research indicates that the biocontrol effect of Streptomyces can be highly improved by transforming the exogenous resistance gene, i.e. chit42from Trichoderma, which not only enhances the production of antibiotics, but also provides a supplementary function by degrading the cell walls of the pathogens.
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Liu, Yiqi,Song, Wenlong,Li, Ningning,Bai, Linquan,Ji, Yanchao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6
This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.
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Yiqi Liu,Wenlong Song,Ningning Li,Linquan Bai,Yanchao Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6
This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.
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Lee, Mi-Jin,Kong, Dekun,Han, Kyuboem,Sherman, David H,Bai, Linquan,Deng, Zixin,Lin, Shuangjun,Kim, Eung-Soo Springer International 2012 Applied microbiology and biotechnology Vol.95 No.1
<P>Polyene antibiotics such as nystatin are a large family of very valuable antifungal polyketide compounds typically produced by soil actinomycetes. Previously, using a polyene cytochrome P450 hydroxylase-specific genome screening strategy, Pseudonocardia autotrophica KCTC9441 was determined to contain an approximately 125.7-kb region of contiguous DNA with a total of 23 open reading frames, which are involved in the biosynthesis and regulation of a structurally unique polyene natural product named NPP. Here, we report the complete structure of NPP, which contains an aglycone identical to nystatin and harbors a unique di-sugar moiety, mycosaminyl-(α1-4)-N-acetyl-glucosamine. A mutant generated by inactivation of a sole glycosyltransferase gene (nppDI) within the npp gene cluster can be complemented in trans either by nppDI-encoded protein or by its nystatin counterpart, NysDI, suggesting that the two sugars might be attached by two different glycosyltransferases. Compared with nystatin (which bears a single sugar moiety), the di-sugar containing NPP exhibits approximately 300-fold higher water solubility and 10-fold reduced hemolytic activity, while retaining about 50% antifungal activity against Candida albicans. These characteristics reveal NPP as a promising candidate for further development into a pharmacokinetically improved, less-cytotoxic polyene antifungal antibiotic.</P>
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