%0 Journal Article
%T Efficient synthesis of L-malic acid by malic enzyme biocatalysis with CO2 fixation.
%A Shi J
%A Fan Y
%A Jiang X
%A Li X
%A Li S
%A Feng Y
%A Xue S
%J Bioresour Technol
%V 403
%N 0
%D 2024 Jul 20
%M 38777233
%F 11.889
%R 10.1016/j.biortech.2024.130843
%X The malic enzyme (ME) catalyzes the synthesis of L-malic acid (L-MA) from pyruvic acid and CO2 with NADH as the reverse reaction of L-MA decarboxylation. Carboxylation requires excess pyruvic acid, limiting its application. In this study, it was determined that CO2 was the carboxyl donor by parsing the effects of HCO3- and CO2, which provided a basis for improving the L-MA yield. Moreover, the concentration ratio of pyruvic acid to NADH was reduced from 70:1 to 5:1 using CO2 to inhibit decarboxylation and to introduce the ME mutant A464S with a 2-fold lower Km than that of the wild type. Finally, carboxylation was coupled with NADH regeneration, resulting in a maximum L-MA yield of 77 % based on the initial concentration of pyruvic acid. Strategic modifications, including optimal reactant ratios and efficient mutant ME, significantly enhanced L-MA synthesis from CO2, providing a promising approach to the biotransformation process.