Use of response surface methodology to evaluate the effect of metal ions (Ca 2+, Ni 2+, Mn 2+, Cu 2+) on production of antifungal compounds by Paenibacillus polymyxa

Abstract

The effects of four metal ions (Ca 2+, Ni 2+, Mn 2+ and Cu 2+) were evaluated on growth and production of antifungal compounds by Paenibacillus polymyxa SQR-21 and a quadratic predictive model was developed using response surface methodology (RSM). The results revealed, Mn 2+ and Ni 2+ showed most positive synergistic interactive affect on production of antifungal compounds followed by the positive interactive synergistic affect of Cu 2+ and Ni 2+ and then Mn 2+ and Cu 2+. While the interactive effect of Ca 2+ with all other three metals inhibited the production of antifungal compounds. The Mn 2+ ( P = 0.0384), Ni 2+ ( P = 0.0004) and Cu 2+ ( P = 0.0117) significantly affected the production of antifungal compounds while the effect of Ca 2+ ( P = 0.1851) was less significant. The maximum growth (OD 600 = 1.55) was obtained at 500 (0), 125 (0), 100 (−2) and 37.5 (0) μM levels and the maximum size of inhibition zone (31 mm) was measured at 400 (−1), 150 (1), 400 (1) and 25 μM (−1) levels of Ca 2+, Mn 2+, Ni 2+ and Cu 2+, respectively. The RSM model provided an easy and effective way to determine the interactive effect of metal ions on production of antifungal compounds by P. polymyxa SQR-21 so that optimum media recipes can be developed to produce maximum amounts of antifungal compounds under laboratory and commercial fermentation conditions.