Effect of transport proteins on L-isoleucine production with the L-isoleucine-producing strain Corynebacterium glutamicum YILW.
Previous studies have shown that the deletion of brnQ from the Corynebacterium glutamicum chromosome results in a significant reduction in L-isoleucine uptake rates, while overexpression of brnFE leads to enhanced L-isoleucine export rates. Given that net excretion rates would be an important factor for high titers of L-isoleucine accumulation, we have tested the notion that decreased L-isoleucine uptake combined with increased L-isoleucine excretion will further improve high-yield strains that are currently used for the industrial-scale production of L-isoleucine. To examine the effect of the two carriers on L-isoleucine accumulation in L-isoleucine producer C. glutamicum YILW, we constructed a brnQ deletion mutant (C. glutamicum YILW∆brnQ) and two brnFE overexpressors (C. glutamicum YILWpXMJ19brnFE and C. glutamicum YILW∆brnQpXMJ19brnFE). Compared to the original strain, the efflux rate of the brnQ mutant increased from 19.0 to 23.6 nmol min(-1) mg (dry wt)(-1) and its L-isoleucine titer increased from 154.3 mM (20.2 g l(-1)) to 170.3 mM (22.3 g l(-1)). The efflux rates of C. glutamicum YILWpXMJ19brnFE and C. glutamicum YILW∆brnQpXMJ19brnFE were 33.5 and 39.1 nmol min(-1) mg (dry wt)(-1), and their L-isoleucine production titers were 197.2 mM (25.9 g l(-1)) and 221.0 mM (29.0 g l(-1)), respectively. Our results suggest that modifications of the transport system could provide a promising avenue for further increasing L-isoleucine yield in the L-isoleucine producer.
Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, China.
Xixian
X
Xie
Lanlan
L
Xu
Jianming
J
Shi
Qingyang
Q
Xu
Ning
N
Chen
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D007532:Isoleucine / Q000096:biosynthesis* / Q000378:metabolism
D001426:Bacterial Proteins; D002352:Carrier Proteins; D007532:Isoleucine