Bioremediation of glyphosate herbicide using pure cultures and bacterial isolates from glyphosate applied maize field

Glyphosate is a post emergence and non-selective herbicide used in both agriculture and non-agriculture areas. During crop development and after crop harvest, glyphosate can be used in no-till agriculture for preparation of fields before planting. The use of glyphosate has a damaging effect on environment due to leaching and sorption in soil. Therefore. it is necessary to remediate glyphosate contaminated soil. Microbial degradation can be used as an efficient strategy to degrade glyphosate. Laboratory degradation and microcosm experiment was conducted to assess the potential of selected pure cultures and glyphosate applied soil enriched cultures. The experiment was performed using five treatments with three different concentrations of glyphosate and three replications. Control was maintained without microbial inoculation/soil sterilization. Four pure cultures Salinicoccus roseus DSM 5351, Salinicoccus hispanicus DSM 5352, Salinicoccus alkaliphilus KCTC 13928, Bacillus subtilis KCTC 3135 were used to assess their degradation potential for glyphosate and compare with soil enriched cultures from glyphosate applied maize field. Periodic sampling was done to assess the degradation potential of pure strains and was compared with soil enriched cultures. Collected samples were run on High Performance Liquid Chromatography for assessing the degradation of glyphosate by comparing it with control treatments. Results with respect to optical density showed that a significant and more efficient growth curve was observed in minimal salt medium (MSM) containing a pure strain Bacillus subtilis KCTC 3135 as compared to Salinicoccus alkaliphilus KCTC 13928 Salinicoccus rose us DSM 5351 and Salinicoccus hispanicus DSM 5352. However soil enriched cultures from glyphosate applied maize field also showed more efficient growth rate as compared to pure cultures. Degradation results of different microbial strains and soil enriched cultures from glyphosate applied maize field showed that soil enriched cultures showed higher degradation efficiency as compared to pure cultures. Among pure cultures, Bacillus subtilis KCTC 3135 showed best degradation efficiency as compared to Salinicoccus alkaliphilus KCTC 13928 Salinicoccus roseus DSM 5351, Salinicoccus hispanicus DSM 5352. From above summarized results, it can be concluded that bacterial cultures have the ability to degrade glyphosate more efficiently.