The Study On The Strain Fermentation Of Nitrite Reductase And Its Application In Cooking Sausage

Nitrite, which is one kind of the coloring agent, not only can make the meat Translucent, but also can prevent the meat from corrupting. However, if nitrite comes into the human body, it could induce cancer and lose the function of carrying Oxygen by changing the normal hemoglobin. For this reason,it is very important to investigate the changing of the nitrite contents in food and degradation mechanism by biology technology.Nitrite reductase have attracted considerable research interest in recent years because its potential application in the food industry. In the paper, we used B.megaterium MPF-906,which was isolated from tobacco waste and soils with nicotine and identified before,produces nitrite reductase,but enzyme activity is not enough as we need.The nitrite reductase production strain B.megaterium MPF-906 was treated with UV,then a genetic stability and high nitrite reductase activity strain was obtained,named Z85.And its nitrite reductase were 28.76 U/mL,which was incerased by 71% as compared with the starting stain.The effects of compositions of culture medium and cultural conditions on nitrite reductase production were investigated. The optimal culture media are:Glucose 1.5 %, (NH4)2SO4 0.1 %, beef extract 0.2 %, KH2PO4 0.07 %,K2HPO4 0.135 %, NaCl 0.1 %, MnSO4·H2O 0.001 %, MgSO4·7H2O 0.02 %, CaCl2·2H2O 0.002 %, NaNO2 0.0138 % .The optimal cultural conditions including incubating temperature,load of shake flask,rotation rate and amount of inoculation are:30℃,160 r/min,initial pH 6.5 and 4 %,respectively. Under this condition,the nitrite reductase reached 45.94 U/mL.The nitrite reductase which comes from Z85 was extracted,and the optimal temperature and pH for enzyme reactivity were 40℃and 6.5 respectively. At 80℃, there still remained about 50 %enzyme activity (good thermal stability).It was in stable state under the condition of pH value between 5.0 and 9.0 and the activity of residual redutase was above 50 % on average.Besides, the nitrite reductase was strongly inhibited by Mn2+, Pb2+ and moderately inhibited by Na+, Fe3+, Mg2+, Al3+(other ions had no evident efects on it within the range of experimental concentration). Adding some alcoholicmaterials and thickening agent etc. into the nitrite reductase solution, the stability of nitrite reductase could be increased. Using glycerol,xanthic pastern and CaCl2 though orthogonal experiments of four elements and three levels, a satisfying p rotective agent, which included glycerin (4 %) , xanthan gum (0.6 %) and CaCl2 (0.15 %) and had a significant effect on the enhancement of the inulinase stability.There is a lower nitrite residual by adding nitrite reductase of the situation:water content 50%,enzymatic treating temperature 85℃,reacting time 2 h,nitrite reductase concentration 2000 U/Kg,electron donor Vc 3.52 g/Kg and salt 2.5 %,15.84 mg/Kg ,which is much lower than GB(30mg/Kg).