Screening a surfactin and iturin A producing strain and characterization of its lipopeptide products

After preliminarily isolated from soil of vegetable gardens by using blood-agar method,eight strains were further examined by oil-spreading test and inhibitory test.Primers were designed according to genes(sfp,ituD,lpa-14) related to surfactin and iturinA synthesis,and one bacterial strain XZ-173 with a broad spectrum of phytopathogens was screened out by PCR of the sfp,ituD,lpa-14 gene.Based on the physiological and biochemical properties and 16S rDNA sequence analysis,it was identified as Bacillus amyloliquefaciens.The FT-IR and HPLC results indicated that the biosurfactnat produced by strain XZ-173 was lipopeptides that contained surfactin and iturin A.The prepared crude lipopeptides reduced the surface tension of water to 26.6 mN/m with a critical micelle concentration(CMC) of 500 mg/L and showed stable emulsification capability and strong inhibition against Rhizoctonia solani and Ralstonia solanacearum.Lipopeptide-producing stain XZ-173 had potential to be used in biological control of soil-borne plant diseases.