The Degradation Pathway of Nitrite by LCR 6013 and the Primary Localization of Its Nitrite Reductase
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Abstract:
The effects of Vc, NaCl on the nitrites degradation by Lactobacillus casei subsp. rhamnosus 6013 (LCR 6013) in the De Man, Rogosa and Sharpe medium (MRS) were investigated. The degradation pathway was confirmed by electron capture gas-chromatography and indophenol blue colorimetric method. The nitrite reductase (NiR) localization was examined by measuring the enzyme activity of different cellular components from LCR 6013 cells. In MRS, the degraded nitrites concentration reached the highest to 9.29 μg/mL and 9.89 μg/mL when NaCl and Vc concentrations were 0.75 % and 0.02 %, respectively. To compare with the control, the degradation effect of treatment was significant (p?0.01). When the initial concentration of nitrites was 10.00 μg/mL, the degradation products contained 28.81?10-6 N2O. The strain LCR 6013 completely degraded the nitrites with initial concentration of 50.00 μg/mL after 16 h incubation And the volume fraction of N2O reached 96.61?10-6 after 14 h. The enzyme activity of nitrites from the periplasm extraction was 2.5 fold higher than that from the cytoplasm extraction. In summary, the effective degradation of nitrites is due to the reaction of the nitrite reductase in the LCR 6013 cell. The most likely pathway of degradation was as follows: NO2-?NO?N2O?N2, rather than ammonification. The degradation products contain N2O gas.
