Biodegradation of nicotine by newly isolated Pseudomonas sp. CS3 and its metabolites.

AIMS

Isolation and characterization of nicotine-degrading bacteria with advantages suitable for the treatment of nicotine-contaminated water and soil and detection of their metabolites.

METHODS AND RESULTS

A novel nicotine-degrading bacterial strain was isolated from tobacco field soil. Based on morphological and physiochemical properties and sequence of 16S rDNA, the isolate was identified as Pseudomonas sp., designated as CS3. The optimal culture conditions of strain CS3 for nicotine degradation were 30°C and pH 7·0. However, the strain showed broad pH adaptability with high nicotine-degrading activity between pH 6·0 and 10·0. Strain CS3 could decompose nicotine nearly completely within 24 h in liquid culture (1000 mg L(-1) nicotine) or within 72 h in soil (1000-2500 mg kg(-1) nicotine) and could endure up to 4000 mg L(-1) nicotine in liquid media and 5000 mg kg(-1) nicotine in soil. Degradation tests in flask revealed that the strain had excellent stability and high degradation activity during the repetitive degradation processes. Additionally, three intermediates, 3-(3,4-dihydro-2H-pyrrol-5-yl) pyridine, 1-methyl-5-(3-pyridyl) pyrrolidine-2-ol and cotinine, were identified by GC/MS and NMR analyses.

CONCLUSIONS

The isolate CS3 showed outstanding nicotine-degrading characteristics such as high degradation efficiency, strong substrate endurance, broad pH adaptability, and stability and persistence in repetitive degradation processes and may serve as an excellent candidate for applications in the bioaugmentation process to treat nicotine-contaminated water and soil. Also, detection of nicotine metabolites suggests that strain CS3 might decompose nicotine via a unique nicotine-degradation pathway.

SIGNIFICANCE AND IMPACT OF THE STUDY

The advantage of applying the isolated strain lies in broad pH adaptability and stability and persistence in repetitive use, the properties previously less focused in other nicotine-degrading micro-organisms. The strain might decompose nicotine via a nicotine-degradation pathway different from those of other nicotine-utilizing Pseudomonas bacteria reported earlier, another highlight in this study.