Growth Inhibition Test of Glyphosate Herbicide For Glyphosate-Degrading-Bacteria Screening

Abstract

Glyphosate is one of the most widely used herbicide for weed eradication. Excessive usage of glyphosate may lead to contamination of soil, water, and crops. Soil bioremediation using microorganisms to degrade glyphosate is an effective and cheap method when the level of glyphosate is higher than maximum permitted level. The resistance of the microorganism to glyphosate can be determined by observing IC 50 parameter. The microorganisms which are resistant to high concentration of glyphosate can be selected as candidate for glyphosate biodegradation process. The objective of this study was to determine IC 50 for consortium bacterial culture isolated from glyphosate-contaminated soil and uncontaminated soil. Generally IC 50 value is determined by measuring optical density, but in this study IC 50 value was determined using total number of cell to observe the real effect of glyphosate toward bacteria cell in the soil. Higher tolerance was observed for bacterial consortium culture isolated from uncontaminated soil (IC 50 is 263.38mg/L) compared with the culture from glyphosate-contaminated soil (IC 50 is 2.04 mg/L). Glyphosate at low concentration below 10 mg/L could increase bacterial growth. This study suggested that the bacteria could use low concentration glyphosate as nutrition source.