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| Construction of bkdFGH and aveD-deleted Doramectin-producing Strains |
| Zhen Liu1,Yuanyuan Pan1,Zaiqing Yang1,Ting Lei |
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Abstract Doramectin is a novel macrolide antibiotics derived from avermectin and widely used as an anti-parasitic drug in animal husbandry. Doramectin can be produced by genetically modified Streptomyces avermitilis with altered avermectin synthesis pathways. Disruption of branched-chain alpha-keto acid dehydrogenase gene cluster (bkdFGH), which encodes the components of the branched-chain alpha-keto acid dehydrogenase(BCDH) complex multi-enzyme system, can direct S. avermitilis to produce effective doramectin (CHC-B1), along with other undesired analogues such as CHC-A1 and -A2, when cyclohexanecarboxylic acid (CHC) is added to the fermentation medium as a precursor. aveD, which encodes avermectin B 5-O-methyltransferase, is reported to be responsible for transforming avermectin "B" component to "A". Deletion of aveD may reduce the amount of CHC-A component in doramectin produced by bkdFGH-deleted S. avermitilis. Here we reported the construction of 2 mutant S. avermitilis strains capable of doramectin biosynthesis. S. avermitilis strain SAV939, an avermectin high-producing strain, was deleted for bkdFGH gene by homologous double crossover to generate mutant strain LZ-01. High performance liquid chromatography (HPLC) analysis demonstrated that LZ-01 could produce effective doramectin (CHC-B1) when CHC was added as a precursor in the fermentation process. Based on that, we further deleted avermectin D(aveD) in LZ-01 and obtained mutant strain LZ-02. Like LZ-01, LZ-02 could also produce CHC-B1 through fermentation, but without the ineffective component CHC-A. This work provides 2 novel doramectin producer mutants from an avermectin-overproducing industrial strain of S. avermitilis, which could potentially become industrial doramectin-producing strains after further improvement.
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Received: 19 August 2015
Published: 05 February 2016
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Corresponding Authors:
Ting Lei
E-mail: leiting@mail.hzau.edu.cn
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