Nitrifying bacteria utilize molecular oxygen to oxidize ammonia to nitrate and occupy a key position in the nitrogen cycle in nature. Being litho-autotrophic organisms, these bacteria tend to produce little biomass, even in well controlled fermenters in the laboratory. In the present study, two nitrifying strains, including ammoniaoxydizing Nitrosomonas sp. DVAl and nitrite-oxydizing Nitrobacter sp. DVN1, were used for demonstrating mass cultivation in a 10 liter fermenter (Satorius, Germany). It has been shown that cultivation of each strain separately could only reach cell densities of 2,5 - 3,8 x 10 exponent 8 cells/ml, mainly due to the inhibitory effect of nitrite in the medium. At the same time, co-cultivation of these two strains allowed to increase cell density to 1,2 - 1,5 x 10 exponent 9 cells/ml since the nitrite produced by the arnmonia-oxydizing strain was immediately utilized by the nitrite-oxydizing strain, and by that way the inhibitory effect of nitrite was minimized. The mass cultivation procedure for the nitrifying bacteria demonstrated in this study coud be a good reference for other studies and applications that require biomass from this litho-autotrophic bacterial group.
Lọc theo danh mục
Lượt truy cập :
20,972,756
Xem toàn văn