Abstract
Genome shuffling is an effective method for the rapid improvement of the production of secondary metabolites. This study used the principle of gene shuffling to enhance the yield of iturin A produced by Bacillus amyloliquefaciens LZ-5. Improvements in lipopeptide yield were evident among four strains subjected to recursive protoplast fusion. The four strains were obtained through mutagenesis processes: nitrosoguanidine, ultraviolet irradiation, and atmospheric and room temperature plasma. A high yield strain with 179.22 mg/l of iturin A was obtained after two rounds of genome shuffling, which was a 2.03-fold increase compared with the wild strain. To evaluate the efficacy of iturin A for control of spoilage yeast in food, the anti-yeast efficacy of iturin A was evaluated in orange juice incubated with Saccharomyces cerevisiae. The juice treated with 0.76 mg/ml iturin A showed a significant (p < 0.05) control on yeast population during the storage, similar to that of the 0.30 mg/ml natamycin. In addition, iturin A showed a tiny effect on chemical-physical characteristics of orange juice. Our results provide a basis for the application of antimicrobial lipopeptide in juice products.
Highlights
Bacillus strains can produce many kinds of secondary metabolites including antimicrobial lipopeptides synthesized by a complex multifunctional enzyme system
The mutants were maintained in the standard potato dextrose agar (PDA) media at 37◦C, and the inoculums were prepared in potato dextrose broth (PDB) media shaking at 180 rpm at 37◦C for 12 h
This study demonstrates that the gene shuffling is an effective method to accelerate the evolution of strains by improving the iturin A production in B. amyloliquefaciens
Summary
Bacillus strains can produce many kinds of secondary metabolites including antimicrobial lipopeptides synthesized by a complex multifunctional enzyme system. They are reported to have a genomic basis for the biosynthesis of polyketide or nonribosomal peptide derivatives due to the presence of polyketide synthases (PKSs) and nonribosomal peptide-synthetase (NRPS). Antimicrobial lipopeptides are used in the cosmetic industries (Kanlayavattanakul and Lourith, 2010), food (Bie et al, 2005) They can enhance oil recovery (Schaller et al, 2004) and improve the bioremediation of oil-contaminated sites (Mulligan et al, 2001). Iturin A is produced mainly by Bacillus amyloliquefaciens and B. subtilis, but its application is limited by low production
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