Development of a regulatable low-temperature protein expression system using the psychrotrophic bacterium, <i>Shewanella livingstonensis</i> Ac10, as the host

A low-temperature protein expression system is useful for the production of thermolabile proteins. We previously developed a system that enables constitutive protein production at low temperatures, using the psychrotrophic bacterium <i>Shewanella livingstonensis</i> Ac10 as the host. To increase the utility of this system, in the present study, we introduced a repressible promoter of the <i>trp</i> operon of this bacterium into the system. When ß-lactamase was produced under the control of this promoter at 18°C and 4°C, the yields were 75 and 33 mg/L-culture, respectively, in the absence of L-Trp, and the yields were decreased by 72% and 77%, respectively, in the presence of L-Trp. We also found that 3-indoleacrylic acid, a competitive inhibitor of the <i>Escherichia coli trp</i> repressor, increased the expression of the reporter gene. This repressible gene expression system would be useful for regulatable recombinant protein production at low temperatures. A regulatable low-temperature protein expression system was constructed by using a cold-adapted bacterium as the host and its trp operon promoter.