A Recombinant Lipoprotein Antigen against Lyme Disease Expressed in E. coli*. Fermentor Operating Strategies for Improved Yield

Decorin-binding lipoprotein, lpp-DBP, a bacterial surface adhesin, shows promise as a vaccine against Lyme disease. It is expressed in recombinant E. coli as an undesirable 20.5 KDa apoprotein that is subsequently lipidated in vivo to the desired 22 KDa lppDBP form. This study defines fermentation conditions for maximizing lpp-DBP yield. Super broth medium, a low post-induction temperature (30 °C), and a glucose feed based on dissolved oxygen resulted in high lpp-DBP yield and minimized apoprotein formation. Since cells lysed within 2-3 h after induction, the cell yield was maximized by growing cells to high cell density prior to induction. Compared to a glucose feed based on maintaining a constant fermentor glucose concentration (Glucose-Stat), feeding based on maintaining a constant dissolved oxygen level (DO-Stat) improved yields. Also, a dissolved oxygen level of 60% (air saturation) was best, as no product degradation was detected by Western blotting and SDS-PAGE. Acetic acid levels under both modes of glucose feed were sufficiently low, and no adverse growth effects were observed.