title: Developing a high-throughput screening method for threonine overproduction based on an artificial promoter.
abstract: BACKGROUND
  L-Threonine is an important amino acid for animal feed. Though the industrial fermentation technology of threonine achieved a very high level, there is still significant room to further improve the industrial strains. The biosensor-based high-throughput screening (HTS) technology has demonstrated its powerful applications. Unfortunately, for most of valuable fine chemicals such as threonine, a HTS system has not been established mainly due to the absence of a suitable biosensor. In this study, we developed a HTS method to gain high-yielding threonine-producing strains.
  
  
  RESULTS
  Novel threonine sensing promoters including cysJp and cysHp were discovered by proteomic analyses of Escherichia coli in response to extracellular threonine challenges. The HTS method was constructed using a device composed of the fused cysJp and cysHp as a promoter and a linked enhanced green fluorescent protein gene as a reporter. More than 400 strains were selected with fluorescence activated cell sorting technology from a library of 20 million mutants and tested within 1 week. Thirty-four mutants have higher productivities than the starting industrial producer. One mutant produced 17.95 % more threonine in a 5-L jar fermenter.
  
  
  CONCLUSIONS
  This method should play a functional role for continuous improvement of threonine industry. Additionally, the threonine sensor construction using promoters obtained by proteomics analyses is so convenient that it would be easily extended to develop HTS models for other biochemicals.
authors: College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300222, People's Republic of China. lyn8952@163.com.|Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. lyn8952@163.com.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. lyn8952@163.com.
authors: Ya'nan
authors: Y
authors: Liu
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. li_qg@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. li_qg@tib.cas.cn.
authors: Qinggang
authors: Q
authors: Li
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zheng_p@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zheng_p@tib.cas.cn.
authors: Ping
authors: P
authors: Zheng
authors: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zhang_zd@tib.cas.cn.
authors: Zhidan
authors: Z
authors: Zhang
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. liu_yf@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. liu_yf@tib.cas.cn.
authors: Yongfei
authors: Y
authors: Liu
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. sun_cm@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. sun_cm@tib.cas.cn.
authors: Cunmin
authors: C
authors: Sun
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. cao_gq@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. cao_gq@tib.cas.cn.
authors: Guoqiang
authors: G
authors: Cao
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zhou_wj@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zhou_wj@tib.cas.cn.
authors: Wenjuan
authors: W
authors: Zhou
authors: School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, 211800, People's Republic of China. 1255653441@qq.com.
authors: Xiaowei
authors: X
authors: Wang
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zhang_dw@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. zhang_dw@tib.cas.cn.
authors: Dawei
authors: D
authors: Zhang
authors: College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300222, People's Republic of China. tony@tust.edu.cn.
authors: Tongcun
authors: T
authors: Zhang
authors: Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. sun_jb@tib.cas.cn.|Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. sun_jb@tib.cas.cn.
authors: Jibin
authors: J
authors: Sun
authors: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. ma_yh@tib.cas.cn.
authors: Yanhe
authors: Y
authors: Ma
mesh_terms: D019149:Bioreactors; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D005818:Genetic Engineering / Q000379:methods; D057166:High-Throughput Screening Assays; D011401:Promoter Regions, Genetic; D040901:Proteomics; D013912:Threonine / Q000096:biosynthesis*
chemical_list: D013912:Threonine