Effect of the pat, fk, stpk gene knock-out and mdh gene knock-in on mannitol production in Leuconostoc mesenteroides

Leuconostoc mesenteroides can be used to produce mannitol by fermentation, but the mannitol productivity is not high. Therefore, in this study modify the chromosome of Leuconostoc mesenteroides by genetic methods to obtain high-yield strains of mannitol production. In this study, gene knock-out strains and gene knock-in strains were constructed by a two-step homologous recombination method. The mannitol productivity of the pat gene (which encodes phosphate acetyltransferase) deleteon strain (Δpat::amy), fk gene (which encodes fructokinase) deleteon strain (Δfk::amy) and stpk gene (which encodes serine-threonine protein kinase) deleteon strain (Δstpk::amy) were all increased compared to the wild type, and the productivity of mannitol for each strain was 84.8%, 83.5% and 84.1% respectively. The mannitol productivity of the mdh gene (which encodes mannitol dehydrogenase) knock-in strains (Δpat::mdh, Δfk::mdh and Δstpk::mdh) was increased to a higher level than that of the single-gene deletion strains, and the productivity of mannitol for each was 96.5%, 88% and 93.2%, respectively. The multi-mutant strain ΔdtsΔldhΔpat::mdhΔstpk::mdhΔfk::mdh had mannitol productivity of 97.3%. This work shows that multi-gene knock-out and gene knock-in strains have the greatest impact on mannitol production, with mannitol productivity of 97.3% and an increase of 24.7% over wild type. This study used the methods of gene knock-out and gene knock-in to genetically modify the chromosome of Leuconostoc mesenteroides. It is of great significance that we increased the ability of Leuconostoc mesenteroides to produce mannitol and revealed its broad development prospects.