Combining metabolic engineering and adaptive evolution to enhance the production of dihydroxyacetone from glycerol by Gluconobacter oxydans in a low-cost way

Gluconobacter oxydans can rapidly and effectively transform glycerol to dihydroxyacetone (DHA) by membrane-bound quinoprotein sorbitol dehydrogenase (mSLDH). Two mutant strains of GDHE Δadh pBBR-PtufBsldAB and GDHE Δadh pBBR-sldAB derived from the GDHE strain were constructed for the enhancement of DHA production. Growth performances of both strains were largely improved after adaptively growing in the medium with glucose as the sole carbon source. The resulting GAT and GAN strains exhibited better catalytic property than the GDHE strain in the presence of a high concentration of glycerol. All strains of GDHE, GAT and GAN cultivated on glucose showed enhanced catalytic capacity than those grown on sorbitol, indicating a favorable prospect of using glucose as carbon source to reduce the cost in industrial production. It was also the first time to reveal that the expression level of the sldAB gene in glucose-growing strains were higher than that of the strains cultivated on sorbitol.