Journal of Pure and Applied MicrobiologyVol. 9 No. 3

Optimization of Medium to Improve the Antifungal Activity of Bacillus atrophaeus XW2 using Response Surface Methodology

Huayi Huang, Dimei Yu, Yan Sun and Chengming Tian

The Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University, No.35, Tsinghua Eastern Road, Haidian District, Beijing 100083, China.

Received on 28 April 2015 and accepted on 04 June 2015

 

ABSTRACT

Bacillus atrophaeus XW2, isolated from poplar leaves, shows a strong inhibitory effect against the fungus Colletotrichum gloeosporioides, which causes poplar anthracnose. The effects of different medium components on antifungal activity against C. gloeosporioides were examined with a view to improving the antifungal activity of XW2. Plackett-Burman design revealed that among eight components within the basal medium, glucose, peptone, and yeast extract had positive effects on antifungal activity. The steepest ascent method determined the local maximums for these important factors. Central composite design then determined the optimum levels of these factors to be 22.64 g/L (glucose), 11.93 g/L (peptone), and 1.85 g/L (yeast extract). Overall, a 52.15% increase in antifungal activity was obtained after growth in optimized medium compared with basal medium. The antifungal activities of the B. atrophaeus XW2 lipopeptides and proteins were effectively increased by 44.84% and 44.83%, respectively. Moreover, after optimization, strain XW2 displayed strong antagonism towards fungal phytopathogens belonging to various taxonomic groups, with inhibition rates ranging from 69.55% to 100%.

Keywords : Bacillus atrophaeus, antifungal activity, medium optimization, Plackett-Burman design, Central composite design, response surface methodology.