Design Of Microchannel Immobilized Urease Cleas Reactor And Study On Urine Treatment

In recent years,large progress has been made in the study on crosslinked enzyme aggregates(CLEAs),but CLEAs still have many problems in CLEAs,such as high viscosity,inconvenient reuse and few application scenarios,which limit the development of CLEAs.In this paper,CLEAs and microchannel reactor were combined to prepare microchannel reactor immobilized urease CLEAs(MRIUC).MRIUC not only can overcome the shortcomings of CLEAs,but also can exert the advantages of microchannel reactor,such as large specific surface area and quick mass transfer.MRIUC is used to treat urine on the space station.In this study,firstly,the preparation and condition optimization of urease CLEAs were explored;secondly,the materials for microchannel reactor preparation was screened in terms of enzyme immobilization;then,the conditions for CLEAs immobilization in microchannel reactor were studied;finally,the effect and influencing factors of urine treatment by microchannel reactor with immobilized urease CLEAs were explored.The experiment will provide a new solution for the treatment of urine wastewater in the space station.The main results are as follows:(1)The study on the preparation of urease CLEAs showed that urease CLEAs activity was the highest as 45%of free urease under the following conditions:10 mg/ml enzyme solution,60%acetone as precipitant,7%glutaraldehyde as crosslinking agent,precipitation/crosslinking time 1h,and25℃.(2)The study on material screening for microchannel reactor preparation showed that polymethyl methacrylate was the most suitable material for immobilizing urease CLEAs among the five materials.CLEAs immobilized on PMMA showed the highest activity as 2.7U/cm~2under the following conditions:20 mg/ml enzyme solution,50%acetone,5%glutaraldehyde,precipitation/crosslinking time 1 h,and 25℃.Immobilized CLEAs showed good characteristics.For example,its residual activity could be observed after 40 min under 60℃;residual activity was 45%after 4 cycles reuse,and was 72%after 28 d storage in 4℃;its activity was stable in range of p H 5.0-9.0.(3)The study on preparation of microchannel reactor with immobilized urease CLEAs(MRIUC)showed that MRIUC showed the high activity as0.49U/cm~2under when the solution mixture of 10 mg/ml enzyme solution,20%acetone and 2%glutaraldehyde was passed through the microchannel reactor at the flow rate of 50μl/min for 1 h at 25℃.(4)The study on the influence factors of simulated urine treated by MRIUC showed that the best treatment effect was obtained when urine(urea concentration 1.86 g/L)was passed through MRIUC at the flow rate of 200μl/min at 25℃and hydraulic retention time was 5 min.The treatment efficiency increased from 62μmol/h to 106μmol/h when urine p H increased from 6 to 8.MRIUC showed good performance.the treatment efficiency was 51μmol/h with residual activity of 34%after 40 min under 60℃.The treatment efficiency was 26μmol/h with residual activity of 64%after 3 cycles reuse.After storage at 4℃for 28 days,the treatment efficiency was 42μmol/h with residual activity of 58%.However,MRIUC activity recovery was poor,which may be due to excessive urease loss and inactivation.