Repeated aspartate tags improve functional expression of Candida antarctica lipase B in recombinant Escherichia coli

 Escherichia coli is the best-established microbial host strain for production of proteins and chemicals, but has a weakness for not secreting high amounts of active heterologous proteins to the extracellular culture medium, of which origins belong to whether prokaryotes or eukaryotes. In this study, Candida antarctica lipase B (CalB), a popular eukaryotic enzyme which catalyzes a number of biochemical reactions and barely secreted extracellularly, was expressed functionally at a gram scale in culture medium by using a simple amino acid-tag system of E. coli. New fusion tag systems consisting of a pelB signal sequence and various anion amino acid tags facilitated both intracellular expression and extracellular secretion of CalB. Among them, the N-terminal five aspartate tag changed the quaternary structure of the dimeric CalB and allowed production of 1.9 g/L active CalB with 65 U/ml activity in culture medium, which exhibited the same enzymatic properties as the commercial CalB. This PelB anion amino acid tag-based expression system for CalB can be extended to production of other industrial proteins hardly expressed and exported from E. coli, thereby increasing target protein concentrations and minimizing purification steps.