title: A novel biocatalyst for efficient production of 2-oxo-carboxylates using glycerol as the cost-effective carbon source.
abstract: BACKGROUND
  The surplus of glycerol has increased remarkably as a main byproduct during the biofuel's production. Exploiting an alternative route for glycerol utilization is significantly important for sustainability of biofuels.
  
  
  RESULTS
  A novel biocatalyst that could be prepared from glycerol for producing 2-oxo-carboxylates was developed. First, Pseudomonas putida KT2440 was reconstructed by deleting lldR to develop a mutant expressing the NAD-independent lactate dehydrogenases (iLDHs) constitutively. Then, the Vitreoscilla hemoglobin (VHb) was heterologously expressed to further improve the biotransformation activity. The reconstructed strain, P. putida KT2440 (ΔlldR)/pBSPPcGm-vgb, exhibited high activities of iLDHs when cultured with glycerol as the carbon source. This cost-effective biocatalyst could efficiently produce pyruvate and 2-oxobutyrate from dl-lactate and dl-2-hydroxybutyrate with high molar conversion rates of 91.9 and 99.8 %, respectively.
  
  
  CONCLUSIONS
  The process would not only be a promising alternative for the production of 2-oxo-carboxylates, but also be an example for preparation of efficient biocatalysts for the value-added utilization of glycerol.
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Yujiao
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Yingxin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Tianyi
authors.initials: T
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Binbin
authors.initials: B
authors.lastname: Sheng
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China ; State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240 People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, 250100 People's Republic of China.
authors.forename: Cuiqing
authors.initials: C
authors.lastname: Ma
keywords: 2-Oxo-carboxylate; Biocatalyst; Glycerol; NAD-independent lactate dehydrogenase; Pseudomonas putida KT2440