LAUSR

Here, we report the one-step secretory production of D-lactate (LA)-based oligomers (D-LAOs) by engineered Escherichia coli from glucose. Notably, D-LAOs are spontaneously secreted into the medium without the introduction of exogenous exporters. This study was originated from the finding that a small amount of oligo[LA-co-3-hydroxybutyrate(3HB)] was secreted by the cells expressing the D-specific LA-polymerizing enzyme (LPE). To increase D-LAOs production, we attempted to increase the frequency of chain transfer (CT) reaction of LPE using CT agents, which bear alcoholic moiety. As the result, addition of diethylene glycol into the culture medium was found to be particularly effective. The highest yield of D-LAOs production of 8.3 ± 1.5 g L−1 from 20 g L−1 glucose was 57% of the theoretical maximum. Furthermore, we demonstrated the covalent conjugation of diethylene glycol at the carboxyl terminal of D-LAOs by NMR analyses. The secreted D-LAOs have the potential to be used as precursors of lactide, enablin...