Optimization of Medium Composition for Lipopeptide Production from Bacillus subtilis N7 using Response Surface Methodology

-Ser) cycledwith a β-amino fatty acid. The surfactin family encom-passes structural variants, but all the members of this familyare heptapeptides interlinked with a β-hydroxy fatty acid toform a cyclic lactone ring structure. Fengycin are lipode-capeptides with an internal lactone ring in the peptide moi-ety and with a β-hydroxy fatty acid chain that can besaturated or unsaturated [12]. Because of their amphiphilicnature, lipopeptides readily associate with and tightlyanchor into lipid layers; in addition they exhibit antagonisticactivities against several plant pathogens by interfering withbiological membrane integrity in a dose-dependent manner[7]. Along with their surface activity and wide spectrum ofantibiotic activity, biologically-derived lipopeptides haveadvantages over synthetic chemical fungicides, specificallylow toxicity, low allergic effect on humans and animals, andhigh biodegradability [14].To meet the need for lipopeptides, most previous workemphasized the isolation and screening of hyper-producingmicroorganisms [2] that were cultured via submerged fer-mentation (SMF) [16] or solid-state fermentation (SSF) [11].Fermentation processes mostly used organic nitrogen, car-bon, and potassium salt. However, few studies have beendevoted to investigating trace elements and precursorssuch as Fe