Isolation and Purification of Nitrite Reductase and Electron Donor from Lactobacillus casei LCR 6013 and Their Synergetic Degradation of Nitrites
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Abstract:
After Lactobacillus casei LCR 6013 was induced with sodium nitrite solution (10.00 mg/L) and treated with lysozyme, the crude enzyme solution was precipitated using 30% and 60% saturated ammonium sulfate solution, respectively. The precipitates were dissolved and dialyzed to obtain protein solution I and protein solution II, respectively, which were purified by anion DEAE Sepharose Fast Flow column chromatography and SephadexG-100 gel filtration. The nitrite reductase (NiR) purified from protein solution II could degrade nitrite only after adding cytochrome C. A total of 0.54 mg of active enzyme protein, with an activity of 1851.20 U/mg, was obtained from 1.00 L of LCR 6013 fermentation liquid, and the specific NiR activity of the purified enzyme increased by 16-fold with an yield of 2.08%. The monomer molecular weight of NiR was about 45.00 ku based on SDS-PAGE patterns. Moreover, when the protein purified from protein solution I was added to NiR from LCR 6013, it showed the ability to degrade nitrites. The protein was identified as an electron donor protein (ElD). The monomer molecular weight of the ElD, as confirmed using SDS-PAGE, was about 13.00 ku, which is the same as that of cytochrome C. It was also found that when combined with NiR from LCR 6013, the ElD from LCR 6013, cytochrome C, ferrous sulfate, and sodium sulfite could degrade 75.00 mg/L of sodium nitrite completely within 48 h, but ElD from LCR 6013 and cytochrome C were the most effective for nitrite degradation.
