Improved L-threonine production of Escherichia coli mutant by optimization of culture conditions.
L-threonine production was investigated in a minimal salt medium using L-threonine-overproducing Escherichia coli MT201, derived from E. coli K-12. It was observed that dry cell weight reached 12.5 g/l with 15.9 g/lL-threonine. To increase dry cell weight and L-threonine production, the fermentation process was optimized. When biotin was added as growth factor, L-threonine production reached 52.0 g/l from 15.9 g/l without biotin. Dry cell weight and L-threonine production were further increased by continuous feeding of the feed media with an optimized L-methionine concentration (5.0 g/l). However, high-cell-density culture caused oxygen-limited condition, which resulted in the accumulation of organic acids. To overcome this problem, oxygen-enriched air was supplied to the fermentor with the minimal salt medium. Under these optimal conditions, we achieved an L-threonine production of 80.2 g/l in the minimal salt medium.
Division of Food and Biotechnology, Kyungnam University, 449 Wolyoung-dong, Masan 631-701, Republic of Korea.
Man-Hyo
MH
Lee
Hong-Weon
HW
Lee
Jin-Ho
JH
Park
Jung-Oh
JO
Ahn
Joon-Ki
JK
Jung
Yong-Il
YI
Hwang
D000388:Air; D001431:Bacteriological Techniques; D001710:Biotin / Q000494:pharmacology; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D007218:Industrial Microbiology / Q000379:methods*; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D012492:Salts; D013912:Threonine / Q000096:biosynthesis*
D003470:Culture Media; D012492:Salts; D013912:Threonine; D001710:Biotin; D010100:Oxygen