Biodegradation of Carbendazim (CRD) by Microorganisms Isolated from Pesticides Contaminated Soil

Abstract

Excessive use of pesticides has been known to create hazardous to the environment, including affecting soil fertility may also impart toxicity in living organisms. Presently, there have been biological approaches implicated to reduce or eradicate pesticides through physical and chemical methods are inefficient. Microorganisms have a potential to mineralize carbendazim with the help of nutrient minimal mineral salt (MMS) medium and soil. Microorganisms were developed resistant against carbendazim MMS medium and they were identified based on its colony morphological characters and 16s rDNA gene sequencing. A total of four bacteria were identified and evaluated for the degradation of Carbendazim. Initially, all bacteria were grown in MMS media supplemented with fungicide to acclimatized and use Carbendazim as sole source of Carbon. The chemical oxygen demand (COD) was carried out and removal of Carbendazim were recorded after 3, 7, 11 and 14 days of incubation period. Bioremediation of carbendazim was analysed in three defined concentration as 100 mg/l, 200 mg/l, and 300 mg/l in μg/ml ratio. After every 14 days interval, the final concentration of Carbendazim and their residues were determined by HPLC technique. HPLC profiling revealed that P. aeruginosa degrade the carbendazim up to 90.03%, 79.22% and 64.42% followed by P. fluorescens 72.33%, 71.83% and 55.08% at three defined concentrations respectively. Microbial consortium with cow dung slurry was also tested to degrade Carbendazim in the soil and it was observed that COD was reduced while 70.48 % degradation was recorded. HPLC-MS analysis found 2-aminobenzimidazole (134.48 m/z) and unknown metabolite with molecular ions (M+) of m/z 132.91, 159.99, 192.01 and 218.90. The toxicity of Carbendazim was observed on fish and seed germination of wheat and mung bean. In fish assay, the survival period of fishes was high in Carbendazim degraded compounds as compared to the aquarium containing pure Carbendazim. Similarly, seed germination of both wheat and mung bean were found to be grater in Carbendazim degraded residues than pure Carbendazim. It indicates that microbial degradation of Carbendazim is eco-friendly (less toxic) to the microbial population as the degraded residues exhibited low toxicity to fish and seed germination of wheat and mung bean. Out of four tested bacteria, P. aeruginosa was found to be most potential followed by P. fluorescence for degradation of Carbendazim. Both are capable to utilize Carbendazim as a sole source of carbon and energy it convert into nontoxic compounds, therefore obtained metabolites are eco-friendly. This technique can be applied on large scale to degrade the toxic compound in soil and also beneficial for soil remediation.