Enhancement of avermectin and ivermectin production by overexpression of the maltose ATP-binding cassette transporter in Streptomyces avermitilis.
ABSTRACT We investigated the function of maltose ABC transporter system encoded by malEFG-a and the effect of its overexpression on antibiotic production in Streptomyces avermitilis. A malEFG-a deletion mutant was unable to grow in a minimal medium with maltose as sole carbon source and produce avermectin. Maltose utilization and avermectin production were restored by introduction of a single copy of malEFG-a. RT-PCR analysis showed that the expression of malE-a was induced by maltose, and was strongly repressed by glucose. When multi-copy, integrative malEFG-a gene expression vectors were introduced into wild-type strain ATCC31267 and ivermectin-producer OI-31, antibiotic production increased by 2.6- to 3.3-fold and the time required for fermentation decreased by about 10%. The overexpression of malEFG-a improved the utilization rate of starch, and thereby enhanced avermectin production. Such an approach would be useful for the improvement of commercial antibiotic production using starch as the main carbon source in the fermentation process.
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ABSTRACT: Avermectins (AVMs), produced by Streptomyces avermitilis MA-4680 (or ATCC 31267, NRRL 8165, NCBIM 12804), are 16-member macrocylic lactones that play very important functions as bactericidal and antiparasitic agents against nematodes and anthropods, as well as Mycobacterium tuberculosis H37Rv. Since its discovery in 1975, use of AVM has been widely spreading around the globe. To date, the whole genome sequence of S. avermitilis K139 has been acquired, in which the AVM biosynthetic gene cluster was the most highly investigated to mine the genes responsible for functional as well as regulatory roles. Therefore, significant progress has been achieved for understanding and manipulating the biosynthesis, improved production, regulation mechanism, side effects, as well as the resistance of AVMs and their derivatives. These findings will facilitate further strain improvement and biosynthesis of novel derivatives bearing stable and improved biological activities, as well as overcoming the resistance mechanism to open up a bright period for these compounds. In this review, we have summarized and analyzed the update in advanced progress in biochemistry and biotechnological approaches used for the production of AVMs and their derivatives.Applied Microbiology and Biotechnology 08/2014; · 3.81 Impact Factor
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ABSTRACT: Streptomyces lydicus has been reported to produce antibiotic streptolydigin. Pitching ratios play crucial roles in primary and secondary metabolism of Streptomyces bacteria. The higher pitching ratio (30%, v/v) significantly enhanced the levels of streptolydigin products in S. lydicus. Proteome analysis revealed that betaglucosidase and UTP-glucose-1-phosphate uridylyltransferase were up-regulated to accelerate the starch hydrolyzation at the high pitching ratios. Enhancement in the levels of UDPN-acetylmuramoylalanyl-D-glutamate-2, 6-diaminopimelate ligase and glycine cleavage system aminomethyltransferase were involved in the conversion of amino acids into secondary metabolites. Additionally, the expression levels of PfkA2, PfkA3, Zwf2, SucD, GalE1, GatB, TktA1 and ThcA, associated with glycolysis, pentose phosphate pathway, TCA cycle and amino acid metabolism, were dramatically elevated at high pitching ratios, which play important roles in the enhanced streptolydigin production in S. lydicus E9. Interestingly, the levels of proteins (glutamine synthetase I, glutamate synthase subunit beta and glutamine synthetase) were down-regulated with the increases of pitching ratios and fermentation progress, revealing that pitching ratio altered the glutamine synthetase levels and consequently regulated the streptolydigin production of S. lydicus E9. The up-regulation of proteins (eg, aldehyde dehydrogenase and alkyl hydroperoxide reductase) was involved in the redox-based regulation network triggered by an imbalance of the intracellular cell redox homeostasis and by crosstalk with secondary metabolism at the higher pitching ratio. These results settle new insights into physiological facts of S. lydicus E9 in responses to pitching ratios and will eventually improve the antibiotic production schemes in industry.Biotechnology and Bioprocess Engineering 17(5). · 1.22 Impact Factor
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ABSTRACT: The S-adenosylmethionine synthetase gene (metK) from Streptomyces avermitilis was cloned into multi-copy vector pIJ653 and integrative vector pSET152 yielding two metK expression plasmids pYJ02 and pYJ03, respectively. When wild-type strain ATCC31267 was transformed with these two plasmids, avermectin production was increased about 2.0-fold and 5.5-fold, respectively. The introduction of integrative expression plasmid pYJ03 into the engineered strain GB-165, which produces only avermectin B, promoted the production of avermectin approximately 2.0-fold. However, introduction of pYJ02 did not influence avermectin accumulation in GB-165. Moreover, transformation of the avermectin-overproducing industry strain 76-05 with these two plasmids did not stimulate avermectin production. These results showed that there were different effects of metK expression levels on avermectin production in various S. avermitilis strains. Additionally, the transcript levels of metK, aveR (the avermectin pathway-specific regulatory gene) and aveA1 (one avermectin biosynthesis gene) meet the expectation of fermentation levels of avermectin in wild-type strain and its recombinant strains. The gene expression levels of metK, aveR and aveA1 in GB-165 and 76-05 were much higher then those in wild-type strain, which probably limited the increasement of avermectin by overexpression of metK.World Journal of Microbiology and Biotechnology (Formerly MIRCEN Journal of Applied Microbiology and Biotechnology) 04/2013; · 1.35 Impact Factor