Effect of media and fermentation conditions on surfactin and iturin homologues produced by Bacillus natto NT-6: LC-MS analysis

Abstract

Lipopeptides possess excellent broad spectrum antimicrobial activity. Different lipopeptides have their own unique chemical structures, properties and biological activities. Quantitative analysis of the lipopeptides iturin and surfactin and their homologues produced by Bacillus natto NT-6 subjected to different culture media, shaking speed of rotary shaker, and liquid and solid fermentation methods was conducted using LC-MS. For iturins, liquid-state fermentation in Landy medium at a shaking speed of 160 r min^-1 was the most suitable for maximal homologue production. Addition of 0.4% attapulgite powder increased production by 1.92-fold; activated carbon significantly reduced production. For surfactin homologues, solid-state fermentation in potato dextrose broth medium at shaking speed > 160 r min^-1 was the best. Addition of 0.4% attapulgite powder increased production by 1.96-fold; activated carbon had no effect. Thus it is clear that fermentation conditions can be manipulated to maximize iturin and surfactin production.

Keywords: Antimicrobial lipopeptide; Bacillus natto; Iturin; LC–MS; Surfactin.

Fig. 1

Effect of different culture media on the production of surfactin homologues (a), iturin homologues (b) and lipopeptides (c). Values are expressed as mean ± SD, n = 4. The different letters indicate significant differences between treatments (p < 0.05). LB lysogeny broth, NB nutrient broth, LAN Landy medium, PDB potato-dextrose broth

Fig. 2

Concentration of surfactin homologues (a), iturin homologues (b) and lipopeptide (c) production at different shaking speeds. Values are expressed as mean ± SD, n = 5. The different letters indicate significant differences between treatments (p < 0.05)

Fig. 3

Ion chromatogram of iturin and surfactin homologues produced by liquid-state fermentation (a), and solid-state fermentation (b)

Fig. 4

Ion chromatogram of iturin and surfactin homologues produced by Landy medium with added 0.6% activated carbon powder (a) and 0.4% attapulgite powder (b)

Fig. 5

Effect of activated carbon powder (ACP) and attapulgite powder (AP) addition to Landy medium on surfactin homologue concentrations (a), iturin homologue production (b), and lipopeptides production (c). Values are mean ± SD, n = 3. The different letters indicate significant differences between treatments (p < 0.05)