Evaluation of metal ions (Zn(2+), Fe(3+) and Mg(2+)) effect on the production of fusaricidin-type antifungal compounds by Paenibacillus polymyxa SQR-21.

Effect of metal ions (Mg(2+), Zn(2+) and Fe(3+)) on the production of fusaricidin-type antifungal compounds by Paenibacillus polymyxa SQR-21 was studied in liquid culture. First, one-factor; three-level experiments were conducted to find out optimal concentrations of each metal ion for maximum production of fusaricidins. Later, three-factor; five-level experiments were performed and a quadratic predictive model was developed using response surface methodology (RSM). The results indicated that Fe(3+) and Mg(2+) positively affected the growth of P. polymyxa as determined by measuring the OD(600) of the liquid culture. The production of fusaricidin-type antifungal compounds was significantly inhibited by Zn(2+) (P=0.0114) and increased by Mg(2+) (P=0.0051) but the effect of Fe(3+) (P=0.2157) was non-significant. However, a synergistic positive effect of Mg(2+) and Fe(3+) on the production of antifungal compounds was observed. This study sheds lights on the pertinent effects of the individual and combined metal ions on the production of fusaricidins in P. polymyxa. It provides the key information for optimization of the metal ions in the fermentation media to achieve the maximum antibiotic production in this strain. 2010 Elsevier Ltd. All rights reserved.