Modification of aspartokinase III and dihydrodipicolinate synthetase increases the production of l-lysine in Escherichia coli
2016
Xu, Jianzhong | Han, Mei | Ren, Xidong | Zhang, Weiguo
To develop an l-lysine high-yielding strain, the enzymes involved in the l-lysine biosynthetic pathway, including aspartokinase III (AK III) and dihydrodipicolinate synthetase (DHDPS) were investigated. Allosteric enzymes involved in l-lysine production from l-lysine producer Escherichia coli LATR11 were sequenced and showed that AK III with mutation T344M or DHDPS with mutation H56K is more conducive to l-lysine production than AK III with mutation M318I or E250K-M318I-G323D or DHDPS with mutation H118Y. Moreover, an l-lysine high-yielding strain was developed from E. coli LATR11 via overexpression of ppc, lysCᵀ³⁴⁴ᴹ, asd, dapAᴴ⁵⁶ᴷ, dapB, and lysA combined with heterologous expression of Corynebacterium glutamicum ddh. The resulting strain LATR11/pWG-DCSᴹASᴹBHc.gLP showed high l-lysine production (37.2±2.3gL⿿¹) with productivity (QP) of 1.16gL⿿¹h⿿¹ in shake flasks. In fed-batch fermentation, LATR11/pWG-DCSᴹASᴹBHc.gLP produced about 125.6gL⿿¹ of l-lysine with QP of 3.14gL⿿¹h⿿¹ and glucose conversion rate (α) of 58.97% after 40h. From which we got the following conclusions: the enzyme with non-feedback control and high activity, and the high flux through biosynthetic pathway are beneficial to improve l-lysine production in E. coli. These results provide a definite theoretical foundation for breeding amino acid high-yielding strains via genetic engineering from classical producers.
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