Enhanced production of iturin A in Bacillus amyloliquefaciens by genetic engineering and medium optimization

•The promoter PbacA was proven as the most efficient promoter for iturin A synthesis.•Deletion of regulator gene abrB improved iturin A synthetase gene cluster transcription and iturin A production.•The titer of 2013.43 mg/L iturin A was produced by optimizing fermentation medium formulas, increased by 392.15 %.•Enhancing the synthetic capability of iturin A was beneficial for the suppression of A. alternate.