Engineering wild-type robust Pediococcus acidilactici strain for high titer l- and d-lactic acid production from corn stover feedstock

Abstract

Pediococcus acidilactici TY112 producing l-lactic acid and P. acidilactici ZP26 producing d-lactic acid, were engineered from the wild-type P. acidilactici DQ2 by ldhD or ldh gene disruption, and the robustness of the wild-type strain to the inhibitors derived from lignocellulose pretreatment was maintained well. In simultaneous saccharification and fermentation (SSF), 77.66gL−1 of l-lactic acid and 76.76gL−1 of d-lactic acid were obtained at 25% (w/w) solids content of dry dilute acid pretreated and biodetoxified corn stover feedstock. l- and d-Lactic acid yield and productivity were highly dependent on the inhibitor removal extent due to the significant down-regulation on the expressions of ldh and ldhD encoding lactate dehydrogenase by inhibitor, especially syringaldehyde and vanillin at the low concentrations. This study provided a prototype of industrial process for high titer l- and d-lactic acid production from lignocellulose feedstock.