## 3 Results and Discussions
### Expression Change of Genes Related to Phosphotransferase System (PTS)
One gene (_scrA_) associated with sucrose transport, which converted extracellular sucrose into intracellular sucrose 6-phosphate, was down-regulated by 3.86 times. Another gene _sacA_ encoding fructofuranosidase further catalyzed sucrose 6-phosphate to form \(\alpha\)-D-glucose-6-phosphate and D-fructose. D-fructose further formed D-fructose-1-phosphate and FBP by double-phosphorylation. Two _mtlA_ genes involved in mannitol transport, which converted extracellular mannitol to intracellular mannitol-1-phosphate, were down-regulated by 2.43 times and 2.76 times, respectively. In addition, Gene _mtlD_ encoding mannitol-1-phosphate 5-dehydrogenase was down-regulated by 2.75 times, which further catalyzed mannitol-1-phosphate into \(\beta\)-D-glucose6-phosphate. Three genes (_UllaA_, _UllaB_, and _UllaC_) associated with ascorbate transport were down-regulated by 3.14-3.83 times, and these 3 genes converted extracellular L-ascorbate into intracellular L-ascorbate-6-phosphate. The obtained L-ascorbate-6-phosphate was further catalyzed to form xylulos-5-phosphate in the cell, and xylulos-5-phosphate participated in the pentose phosphate pathway. Five genes (_citC_, _citD_, _citE_, _citF_, and _frdA_) encoding the citrate lyase in the two-component system were also down-regulated by 5.75-41.32 times, and the encoded citrate lyase catalyzed citric acid to form oxalacetic acid and acetic acid. However, 10 genes (_lacA_, _lacD_, _lacB_, _galK_, _gatC_, _lacC_, _gatA_, _gatB_, _galE_, and _galT_) related to galactose and galactitol transport were up-regulated by 2.75-9.20 times. These 10 genes were responsible for transporting extracellular galactose and galactitol into the cells to form galactose-6-phosphate and galactitol-1-phosphate which were further converted into fructose-6-phosphate, and the obtained fructose-6-phosphate participated in the glycolysis and pentose phosphate pathways. In general, compared with that in the cells from solid-state fermentation, the transport of various carbohydrates in the cells from liquid-state fermentation was weakened. The possible reason might lie in that the sugars were in a dissolved state in the liquid matrix; thus, the absorption, transport, and utilization of carbohydrates were easier. The expression upregulation of genes related to galactose transport in cells from liquid-state fermentation is worth further study. Expression Change of Genes Related to Glycolysis, Pentose Phosphate Pathway, and Pyruvate Metabolism  
Some genes related to glycolysis were down-regulated in the liquid-state fermented cells, compared with the solid-state fermented cells. Specifically, the expression of the gene _fluA_ encoding fructose-bisphosphate aldolase was down-regulated by 8.45 times, and the encoded fructose-bisphosphate aldolase catalyzed the reversible reaction between fructose-1,6-2-phosphate and dihydroxyacetone phosphate or glyceraldehyde triphosphate. Gene _fbp3_ encoding fructose-1,6-bisphosphatase III was down-regulated by 2.64 times. _Gene triA_ encoding the triphosphate isomerase was down-regulated by 3.80 times, and the encoded triphosphate isomerase catalyzed a reversible reaction between dihydroxyacetone phosphate and glyceraldehyde triphosphate. Gene _pgk_ encoding phosphoglycerate kinase was down-regulated by 2.85 times, and the enzyme encoded by this gene catalyzed a reversible reaction between 1,3-2 phosphate and glycerate-3-phosphate. Two _gpmA_ genes encoding 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase were down-regulated by 2.07 times and 2.51 times, respectively, and the enzyme encoded by these two genes catalyzed a reversible reaction between glycerate-3-phosphate and glycerate-2-phosphate. However, gene _eno_ encoding enolase was up-regulated in the liquid-state fermented cells. In general, the expression change of the gene related to glycolysis indicated the downstream glycolysis metabolism were partially weakened, and metabolic flow was changed.