In this study, the yield of EPS produced from S. thermophilus
05-34 reached up to 250 mg/L under the optimal fermentationcondition. Structure analysis showed that EPS produced under this
condition was with a molecular mass of 4.7 105 Da, which was
increased by 9 times compared with that obtained under the
non-optimal fermentation condition. However, the monosaccharide
composition of EPS did not change under the fermentation
conditions tested in this study. Lastly, the transcription level of
epsC was up-regulated by 2.7-fold under the optimal fermentation
condition. Taken all together, the optimal fermentation condition
could up-regulate the transcription level of epsC, which further
improved the molecular mass of EPS from S. thermophilus 05-34
by increasing the polymerization degree of monosaccharide. Our
findings suggested that metabolic engineering is a potential strategy
to improve molecular mass of EPS by enhancing the expression
of epsC.