Production of aminolevulinic acid by recombinant Escherichia coli co-expressing hemA and otsBA using crude glycerol as carbon source

Abstract

This study aimed to develop a microbial process for producing aminolevulinic acid (ALA) using crude glyc-erol. In the culture of ALA-producing cells (Escherichia coli/pH-hemA) in a medium containing crude glyc-erol, the cell density and production were 1.8-fold and 1.2-fold lower than those obtained from pure glycerol, respectively. However, the cell growth and production were improved by supplementing the medium with trehalose (30 or 100 g/l). Engineered cells (E. coli/pH-hemA/pS-otsBA) were constructed to express otsBA and their culture performance was compared with that of control cells (E. coli/pH-hemA/pSTV28). The effects of isopropyl β-D-1-thiogalactopyranoside (IPTG) concentration and the time of induction were examined to improve the cell growth and ALA production in engineered cells cultured using crude glycerol. When 0.6 mM of IPTG was added at the beginning of the exponential growth phase, the ALA produced by cells was 2,121 mg/l, which was comparable to that from pure glycerol. The results demonstrate that otsBA expression endowed cells with the capacity to tolerate the toxicity of crude glycerol for direct use. ? 2016, The Korean Society for Microbiology and Biotechnology.