Abstract:
Nitrate contamination of water bodies has become a serious issue worldwide. This
study aimed to isolate and identify nitrate reducing bacteria and investigate their
nitrate removal efficiency in synthetic medium as the initial step for bioremediation
of nitrate contaminated water. The strain (A22) was isolated from poultry manure
enriched soil sample. Primary screening was carried out on BTB agar plate
supplemented with KNO3. The efficiency of the bacterial strain on nitrate removal
was investigated using mineral salt medium either with glucose or starch as carbon
source at three levels (0.25 %, 0.5 %, and 1 %) with 500 mgl-1 KNO3. Strain A22
reduced 93 % of nitrate without nitrite accumulation in 60 hours of incubation with
0.5 % of glucose while 64.5 % and 52.3 % of nitrate reduction was observed with
0.25 % and 1 % of glucose, respectively. Moreover, strain A22 did not grow in the
medium containing starch. Therefore, among two carbon sources in three levels
(0.25, 0.5, and 1.0 %), glucose 0.5 % showed significantly highest nitrate reduction
and found to be the best level of carbon source for efficient nitrate reduction. Strain
A22 was identified as Pseudomonas aeruginosa by biochemical studies and 16s
rRNA sequencing analysis. The results of this study suggest Pseudomonas
aeruginosa is capable of reducing nitrate in nitrate rich medium. However, due to its
opportunistic pathogenicity, application of the strain for drinking water treatment is
not recommended. Further studies are required to decide the suitability of its
application in waste water treatment.
