Screening Of Aerobic Denitrifiers

It is considered that anaerobic condition was necessary for denitrifying in a long period. But since 1950s, many researchers have demonstrated that aerobic denitrification could be taken place under the aerobic condition. Some strains have the ability of both reducing oxygen and nitrogen at the same time, while some strains have capability of denitrification when there is enough oxygen. For example, strain Thiosphaera pantotropha simulates nitrification and denitrification. Deoxide enzyme activities including Nar,dNir,Nor and Nos can be monitored, but the rate of denitrification is much lower in aerobic condition. The result of 15N marker indicates nitrogen comes from nitrite, which shows nitrogen is not the resultant of nitrifying. Studying deeply aerobic denitrification and isolating aerobic denitrifiers can not only enrich the knowledge of denitrification but also stimulate the innovation of biology denitrifying on waste water treatment.There are three advantages for aerobic denitrifying by aerobic denitrifiers: firstly, nitrification and denitrification can take place in the same reactor, which can lessen space and curtail decrease building fund, so disposal periods is shorten; secondly, less chemicals are used for adjusting pH because of aerobic denitrifiers, that means it can curtail cost; finally, aerobic denitrifiers can be controlled easily in the process of dealing with.Up to now, there are only little reports about aerobic denitrifiers in the world, so it is very important to isolate aerobic denitrifiers. And the purpose of this paper is to isolate some aerobic denitrifiers from soil and study the process of denitrifying and the effect of environment.The soil is got from Yangzhou city. We named six strains after H1,H2,H5,F2,F5 and F6 separately, and they all have good capability of aerobic denitrification. Alignment of 16S rDNA sequences revealed similarity of strain H1 with rhizobium R. taiwanensis is about 98%, so are strains H2 and H5. the similarity of strain F2 and F5 are all about 98% with B.licheniformis, the similarity of strain F6 is about 99.9% with B.subtilis subsp. spizizenii. So we choose H1,F2 and F6 as representation.