Degradation of the Herbicide Bentazon by Soil Microorganisms

제초제 Bentazon 의 토양미생물에 의한 분해

In order to elucidate the degradation of the herbicide bentazon (3-isopropyl-2,1,3-benzothiadiazin-4-one-2,2-dioxide) by soil microorganisms, it was incubated at $23{\pm}1^{\circ}C$ under the submerged and upland soil conditions of the different soils in the Chung Buk area. When bentazon (200 ppm) was incubated in Cheong Won A soil (silty loam; pH, 5.2; organic matter 1.4%) under the submerged condition for 6 months, 6-hydroxy bentazon (1.27%) was formed as the major degradation product and 8-hydroxy bentazon (0.57%) and anthranilic acid (0.13%) were formed as the minor ones. Meanwhile, when 500 ppm of bentazon was incubated in the same soil for 2 months, a trace amount of 6-hydroxy bentazon was formed. Eight strains of microorganisms isolated from the soils did not give any distinct degradation products in the pure culture experiment. The greater dehydrogenase activity in Cheong Won A soil than in Cheong Ju A soil might be related to the greater bentazon-degradability of the former soil than that of the latter. When bentazon (10 ppm) was incubated for 14 days with 14 strains of bacteria and 8 strains of fungi, the identities of which were all known, Rhizopus stolonifer produced 4.6${\sim}$31.6% of anthranilic acid as the major product from batch to batch, with trace amounts of 6-hydroxy bentazon and 8-hydroxy bentazon as minor products. The rest microorganisms did not produce any noticeable products.

토양미생물에 의한 제초제 bentazon(3-isopropyl-2,1,3-benzothiadiazin-4-one-2,2-dioxide)의 분해를 구명하기 위하여 성질이 서로 다른 충북지역의 밭토양 2종과 논토양 2종을 담수 및 밭토양 조건하에서 $23{\pm}1^{\circ}C$ 배양하였다. Bentazon 200 ppm을 처리한 Cheong Won A 토양 (Silty loam; pH, 5.2; 유기물 함량 1.4%)을 6개월 동안 담수상태에서 배양하였을 때 주 분해산물로 6-hydroxy bentazon (1.27%) 및 소량의 8-hydroxy bentazon (0.57%,)과 anthranilic acid (0.13%)가 형성되었다. 한편 bentazon 500 ppm을 처리한 동일토양을 2개월 동안 배양하였을 때는 소량의 6-hydroxy bentazon이 형성되었다. 8종의 미생물을 토양으로 부터 분리하여 순수배양실험을 하였으나 뚜렷한 분해산물을 검출하지 못하였다. Cheong Won A 토양이 Cheong Ju A 토양보다 더욱 큰 dehydrogenase 활성을 나타낸 것으로 보아 전자가 후자보다 더 큰 bentazon 분해력을 가질 것이라고 추측되었다. 세균 14종과 곰팡이 8종에 대하여 bentazun 10 ppm을 처리하고 14일간 배양하였을 때 Rhizopus stolonifer만이 주 분해산물로 anthranilic acid (4.6${\sim}$31.6%) 그리고 소량의 6-hydroxy bentazon과 8-hydroxy bentazon (1.27%)을 형성하였으며, 나머지 미생물에서는 대사산물을 검출할 수 없었다.