Optimized culture medium and fermentation conditions for enzyme production by the salt-tolerant chlorpyrifos-degrading bacterium HY-1

Abstract:

In order to improve the treatment effect of wastewater from pesticide enterprise, it is necessary to study the salt-tolerant characteristics and fermentation conditions of the degrading bacterium. A chlorpyrifos-degrading bacterium Bacillus cereus HY-1 was isolated in laboratory from pesticide wastewater. The optimal fermentation medium and fermentation conditions of HY-1 were selected by single factor and orthogonal test, and the amount of enzyme produced by HY-1 was estimated based on the specific activity of the enzyme. The experimental results were analyzed by the SPSS system. The optimal composition of the culture medium included glucose 6.0 g/L, tryptone 2.2 g/L, K₂HPO₄ 2.0 g/L, K₂HPO₄ 0.2 g/L, MgSO₄·7H₂O 0.1 g/L, NaCl 0.1 g/L, trace elements solution 2 mL/L. The optimal fermentation conditions of HY-1 were: incubation time of the seed culture 16 h, fermentation time 18 h, inoculum size 1% (V/V), initial pH 7.0. The specific activity of the degrading enzyme was not affected while the sodium chloride concentration of the fermentation medium increased from 0 g/L to 30 g/L. To the best of our knowledge, this is the most extremely salt-tolerant bacterium reported that could degrade chlorpyrifos.

Key words:Chlorpyrifos, Degrading enzyme, Culture medium, Fermentation condition optimization, Salt-tolerant bacterium