Construction And Optimization Of Recombinant Strains For Space Urine Wastewater Treatment

The organic acid, urea and salt in urine wastewater is very high,while urea is easily broken down and difficultly to treat. So the spatial urine wastewater treatment has been a problem in space technology of China. The traditional physicochemical methods such as distillation and advanced oxidation method have many defects. Currently, many countries begin to deal with space urine by biological method. In order to treat urine waste water efficiently, the research furtherly construct recombinant strains using genes of Nitrobacter winogradskyi Nb-255 and Nitrosomonas europaea ATCC19718. The main results are as follows:Recombinant plasmids p DHC29::nxr, recombinant E.coli DH5α(p DHC29::nxr) named L2 and E.coli DH5α(p DHC29::nxr, p Trc99a::pro-hao) named L5 with nitrification function were obtained, and recombinant plasmids p Trc99a::pro-hao, recombinant E.coli DH5α(p Trc99a::pro-hao) named L3 and recombinant plasmids p Trc99a::pro-hao+C554+C552, recombinant E.coli DH5α(p Trc99a::pro-hao+C554+C552) named L6 with nitrosation function were also obtained.The recombinant strain L3 has the capacity of converting hydroxylamine hydrochloride into nitrite, and the addition of Cu2+, Fe2+ and Zn2+ could promote the catalytic ability of the recombinant strain. When different concentrations of iron ion and zinc ion were added to the culture fluid, the yield of nitrite nitrogen increased by about 10 times, and the output of nitrite nitrogen increased by 3.059mg/L when Cu2+ was 0.5m M, up to 15 times of the same period; Coexpression of Cytochromes c-554 and Cytochromes c-552 which are related to the electron transfer chain during ammonia oxidation has no significant improvement to the catalytic activity of HAO.The analysis of the recombinant strain L2 was carried out by ion chromatograph and the results showed that L2 had the ability of converting nitrite into nitrate; The inorganic ions such as Mo2+ and Fe3+ had no effect on the conversion capacity of L2; Anaerobic incubation of recombinant L2 showed that NXR can catalyze nitrate to nitrite under anaerobic conditions.The result of shaking-flask cultivation of L5 at ambient pressure was undesirable. The end product was almost 0, and the intermediate product had little yield.