Abstract:The gene lysC1 encoding aspartate kinase AK-1 from a Brevibacterium lactofermentum L-isoleucine producer was sequenced.Compared with the lysC from Corynebacterium glutamicum ATCC13032,there were deletions of two nucleotides 1186G and1187C,leading to the pre-termination of translation.In addition,the following two mutated sites were also identified in lysC1: Ala 279 Thr and Ser 317 Ala.In Escherichia coli BL21,the expression level of lysC1 was lower than that of lysC from B.lactofermentum ATCC13869.The AK-1 had a lower apparent value of specific activity than the wild type AK,but it was not sensitive to the feedback inhibition by the mixture of L-lysine and L-threonine.lysC1 was cloned into an E.coli-Brevibacterium flavum shuttle expression vector pDXW-8 and transformed into wild type B.lactofermentum ATCC13869.The recombinant strain ATCC13869/pDXW-8-lysC1 accumulated 7.5 g/L L-lysine after 90 h flask fermentation and 40 g/L after 72 h batch fermentation.These results would be very useful for constructing a genetically identified L-lysine producing strain with minimum genetic alterations.
