A higher yield of dextran strain Leuconstoc mesenteroides TDS2-19 was isolated from Chinese sauerkraut juice. Effects of the three main factors on exopolysaccharide (EPS) yield were investigated by central composite design (CCD) and the optimum composition was sucrose 117.48g/L, sodium acetate 4.10g/L, and initial pH 6.88. Optimum results showed that EPS yield was increased to 71.23+/-2.25g/L in 48h fermentation, 31.24% higher than before. The molecular weight (Mw) of ESP was 8.79x10(7)Da, as determined by high-performance size-exclusion chromatography (HPSEC). Fourier transform infrared spectra (FT-IR) and nuclear magnetic resonance spectra (NMR) showed that the polysaccharide synthesized by L. mesenteroides TDS2-19 in the MRS medium was dextran with a peak, a linear backbone composed of consecutive α-(1→6)-linked d-glucopyranose units. No branching was observed in the dextran structure. The present study suggested that L. mesenteroides TDS2-19 might be used for the industrial-scale production of linear dextran.

structural analysis, purification, optimization, Dextran, response surface methodology

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
	aDGlcp	99.30	73.20	74.83	71.21	71.76	65.54


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
	aDGlcp	4.97	?	?	?	?	?


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
	aDGlcp	99.30/4.97	73.20/?	74.83/?	71.21/?	71.76/?	65.54/?

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]OC[C@H]1O[C@H]([*])[C@H](O)[C@@H](O)[C@@H]1O

162.141 g/mol (C₆H₁₀R₂O₅, R = next and previous repeats, not counted in mol weight)