Rational selection and engineering of exogenous principal sigma factor (σ(HrdB)) to increase teicoplanin production in an industrial strain of Actinoplanes teichomyceticus

BACKGROUND: Transcriptional engineering has presented a strong ability of phenotypic improvement in microorganisms. However, it could not be directly applied to Actinoplanes teichomyceticus L-27 because of the paucity of endogenous transcription factors in the strain. In this study, exogenous transcription factors were rationally selected and transcriptional engineering was carried out to increase the productivity of teicoplanin in L-27. RESULTS: It was illuminated that the σ(HrdB) molecules shared strong similarity of amino acid sequences among some genera of actinomycetes. Combining this advantage with the ability of transcriptional engineering, exogenous sigma factor σ(HrdB) molecules were rationally selected and engineered to improve L-27. hrdB genes from Actinoplanes missouriensis 431, Micromonospora aurantiaca ATCC 27029 and Salinispora arenicola CNS-205 were selected based on molecular evolutionary analysis. Random mutagenesis, DNA shuffling and point mutation were subsequently performed to generate diversified mutants. A recombinant was identified through screening program, yielding 5.3 mg/ml of teicoplanin, over 2-fold compared to that of L-27. More significantly, the engineered strain presented a good performance in 500-l pilot scale fermentation, which meant its valuable potential application in industry. CONCLUSIONS: Through rational selection and engineering of exogenous transcriptional factor, we have extended the application of transcriptional engineering. To our knowledge, it is the first time to focus on the related issue. In addition, possessing the advantage of efficient metabolic perturbation in transcription level, this strategy could be useful in analyzing metabolic and physiological mechanisms of strains, especially those with the only information on taxonomy.