L-天冬酰胺酶工程菌株培养条件及稳定性

L-天冬酰胺酶工程菌株的酶活和表达水平受菌体生物量和诱导时间的影响。在生物量Ａ６００03×１０左右，热诱导4h酶活力和表达水平可达到较高水平。葡萄糖对酶的生成有阻遏作用，当葡萄糖浓度大于025%时，对工程菌酶的合成造成阻遏。确定了工程菌培养的培养基、pH值、接种量等因素。重组质粒pASN在%E.coli% JM105,TG1和AS1357等宿主菌中具有很好的稳定性，工程菌培养50代以上重组质粒保留90%以上，在LB和M|3培养基中也较稳定。

CULTURE CONDITIONS OF ENGINEERED STRAIN OF L|ASPARAGINASE AND THE RECOMBINANT PLASMID STABILITY

The growth curves of engineered strain JM105(pASN) were different in LB and M-3 media. The expression level and activity of L-asparaginase were affected apparently by both biomass and induction time. Glucose repression of production of L-asparaginase was found. The stability of the recombinant plasmid pASN in different host strains and in LB and M-3 media was determined. After cultivation inLB broth and M-3 media at 30 degrees C for more than 50 generations without antibiotic selection, then induced at 42 degrees C for up to 5 h, the engineered strains were proved to be stable, except for DHA alpha (pASN).