| Compared with chemical surfactants,surfactin has characteristics with high surface activity,non-toxic or low-toxic,biodegradable,without environment pollution.It has also great potential for application in antibacterials,antiviral,anti-tumor,and anti-mycoplasmal activities.However,present studies show that surfactin production of wild strains is almost at the level of mg.The cost of production,separation and purification is also very high.Therefore,the effects of carbon sources,nitrogen sources,amino acids,and fermentation conditions on the surfactin production of B.amyloliquefaciens HM618 were investigated.In addition,the whole genome of B.amyloliquefaciens HM618 was analyzed with genomic sequencing.The main results are as follows:These results showed that sucrose and yeast extracts were beneficial to produce surfactin when pure culture HM618 and co-culture HM618 and Bacillus subtilis(BS)after analysis of single factor experiments.The strain HM618 undre pure culture prefered aspartate while HM618 and BS under co-culture prefers glutamate during surfactin production.The surfactin productions were elevated from 0.724 to 1.876 g/L and from 0.995 to 1.888 g/L under pure culture HM618 and co-culture of HM618 and BS with the the optimized media,respectively.Furthermore,the surfactin production of HM618 in the 5L-fermenter reached to2.651 g/L at 12 h under pure culture after aptimizing fermentation conditions.Compared with pure culture,the surfactin production was increased by 23.5% under the co-culture HM618 and B.cinereal,while the surfactin production was inhibited under the co-culture HM618 and R.solani or Escherichia coli DH5α.The results of the whole genomic analysis revealed that the strain HM618 had4,037,030 bp circular chromosome with a 15,179 bp plasmid,and 6 gene clusters of synthesis lipopeptides including surfactin,bacillibactin,difficidin,bacillaene,fengycin,and bacilysin.Combining above results with metabolic pathway analysis showed that HM618 could prefer to transform asparate and asparate into acetyl-Co A for synthesizing the precursor fatty acid chain of surfactin.These findings provided an experimental basis for further enhancing the surfactin production. |
