토양 분리 박테리아에 의한 2,4-Dichlorophenoxyacetic산의 분해 최적화

Statistical Optimization for Biodegradation of 2,4-Dichlorophenoxyacetic Acid by Soil Isolated Bacterium

2,4-D는 자연에서 잘 분해되지 않아 환경에 대하여 심각하게 문제를 일으키지만 널리 사용되고 있는 제초제이다. 이 연구는 광주광역시 인근 지역 과수원에서 분리한 균주 중 가장 높은 2.4-D분해 활성을 보이는 균주를 선정하여, 동정한 결과 Aeromonas sp.로 판명된 균주를 가지고 표면 반응법(Response Surface Methodology)을 이용하여 2,4-D 분해를 최대화하기 위한 중요한 변수들인, pH,온도, 영양분의 농도들의 최적조건을 고찰하였다. 2,4-D분해에 많은 영향을 미치는 변수는 영양분의 농도로 밝혀졌으며, 통계 분석결과 2,4-D분해 최적 조건은 pH 6.5, 온도 $31.8-32.1^{\circ}C$, 영양분 29.6-30.1 g/1로 밝혀졌다.

2,4-Dichlorophenoxyacetic acid (2,4-D) as a widely used herbicide has caused serious environmental problems because of its difficult decomposition in nature. We isolated the strain capable of metabolizing 2,4-D as sole carbon and energy source by an enrichment culture technique from the 2,4-D contaminated soil collected at orchard in Gwangju, Korea. This strain was identified tentatively as Aeromonas sp. NOH2. With this strain, we established the response surface methodology (Box-Behnken Design) to optimize the principle parameters for maximizing biodegradation of 2,4-D such as culture pH, temperature, and nutrient concentration in liquid batch culture. The ranges of parameters were obtained from preliminary works done at our laboratory and chosen as 5.5, 6.5, and 7.5 for pH, 25, 30, and $35^{\circ}C$ for temperature, and 5, 20, and 35 g/1 nutrient concentration. Initial concentration of 2,4-D was 500 ppm and nutrient source was tryptic soy broth. The experimental data were significantly fitted to a second order polynomial equation using multiple regression. The most important parameter influencing 2,4-D degradation and biomass production was nutrient concentration. For 2,4-D degradation, the optimum values of pH and temperature, and nutrient concentration were obtained at pH (6.5), temperature (31.8 to $32.1^{\circ}C$), and nutrient concentration (29.6 to 30.1.0 g/1).