Optimization of Medium Constituents for ɛ‐Poly‐L‐Lysine Fermentation with Response Surface Methodology

Abstract: ɛ‐Poly‐L‐lysine (ɛ‐PL) is a novel food biopreservative with broad antimicrobial activity. In the present study, single‐factor experiments were applied to screen optimal carbon and nitrogen sources that affect the yield of a ɛ‐PL‐producing strain, Streptomyces violaceusniger , which was obtained in our laboratory recently. Box‐Behnken design and response surface methodology (RSM) were adopted to derive a statistical model for optimizing the composition of the fermentation medium. The results showed that the main factors that affect ɛ‐PL production were glucose, carbon source; peptone, organic nitrogen source; and (NH 4 ) 2 SO 4 , inorganic nitrogen source. The optimum fermentation medium for ɛ‐PL production of S. violaceusniger consisted of (g/L) glucose, 62.49; peptone, 5.71; (NH 4 ) 2 SO 4 , 11.19; MgSO 4 , 0.5; FeSO 4 , 0.03; ZnSO 4 , 0.04; KH 2 PO 4 , 1.36; and Na 2 HPO 4 .12H 2 O, 3.58. When cultured in the optimum medium, the ɛ‐PL production was an average of 0.349 ± 0.025 mg/mL, which was 1.75 times higher than the initial medium. Practical Application: The present study illustrated the potential use of response surface methodology with the Box‐Behnken design in biotechnology. Results from this work suggested that ɛ‐PL production was increased greatly with the optimal medium constituents by the potential organism, S. violaceusniger , which may be a good resource for the industrial production of ɛ‐PL in future.