| In this research, the luc gene coding firefly luciferase (LUC) was amplified by using the DNA of Luciferase reporter vector pXP2 as the template. The luc gene was subcloned into expression vector pQE30 and its product LUC was overexpressed in Escherichia coli M15. There was a single band about 60 kDa on SDS-PAGE gel and the expressed LUC accounted for 50.9 % in E. coli.LUC purified by Ni-NTA affinity chromatography showed a single band about 60 kDa on SDS-PAGE gel, and the specified activity was about 1.43×109 RFU/mg, the purification fold was 10.6 times and the activity recovery was 32.5%. The optimum reaction pH was 7.5. The thermal stability was fine. It was sensitive to light and salt concentration. The metalion such as Mg2+,Zn2+,Mn2+,Ca2+,NH4+could promote the activity of LUC, among the total the promotation of Mg2+ was most obviously.EDTA,BSA and DTT could promote the activity of LUC, and TritonX-100 could protect the activity of LUC in low concertration, but could inhibit the activity of LUC in high concertration. In the single factor of test, the conditon of EDTA 1.0 mmol/L, BSA 0.2%, DTT 4.0 mmol/L, TritonX-100 0.2% was the best. The orthogonal experimental design indicated: DTT 4.0 mmol/L, EDTA 1.5 mmol/L, TritonX-100 0.1%, BSA 0.2% could protect the LUC very well, The relative activity of LUC was 89.18% after 30 days later.The optimum fermentation condition was: pH 7.0,the amount of medium 20%, imcoculum size 2%, the final concentration of IPTG 0.5 mmol/L, 1030 mmol/L Mg2+, the rotating speed 200 r/min, inducing 3.5 h at 37℃. After orthogonal experimental design, the result showed that the initial pH 7.0, 40 mmol/L Mg2+, 2% inoculation amount and the 20% medium amount had the best exprssion of LUC, and the specific activity was 1.63×108 RFU/mg. The fermentation test on fermentation tank indicated that the course of fermentation was the same as in the shake-flask, the activity of LUC was 2.01×108 RFU/mg. So the fermentation of recombinant strain could be amplified.
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