Characterization of dextran produced from Leuconostoc citreum S5 strain isolated from Korean fermented vegetable

A novel exopolysaccharide from Weissella cibaria FAFU821: Structural characterization and cryoprotective activity

Exopolysaccharides produced by Weissella cibaria has attracted increasing attention owing to their biological activity. Here, a strain was isolated from the home-made fermented octopus, which was identified as W. cibaria FAFU821. In addition, the polysaccharide were isolated and purified by cellulose DE-52 column and Sephadex G-100 column, and named EPS821-1. In this work, the structure of EPS821-1 and its cryoprotective activity on Bifidobacterium longum subsp. longum F2 were investigated in vitro. These results suggested that the EPS821-1 is a novel glucan, which mainly consists of α-(1 → 6) linkage with α-(1 → 4), α-(1 → 4,6) and α-(1 → 3,6) residue as branches. In addition, EPS821-1 existed the three-dimensional network structure and exhibited the excellent cryoprotective activities for B. longum subsp. longum F2, which was 2.75 folds higher than that of the controls. This study provided scientific evidence and insights for the application of EPS821-1 as cryoprotection in food field.

Effects ofBacillus subtilisandLeuconostoc mesenteroideson the Quality Characteristics of PotatoGaraetteok

To investigate the texture and cooking properties ofgaraetteokelaborated with potato flour, experimental products were elaborated replacing partially the rice flour, traditionally used, with nonfermented (NF) or fermented potato flour withBacillus subtilis(BS) orLeuconostoc mesenteroides(LM) in percentages of 15% (NF15, BS15, and LM15) and 20% (NF20, BS20, and LM20). The control product (CON) was made using only rice flours. The pH ofgaraetteokwas significantly lower in the BS and LM groups compared to CON and NF. Titratable acidity was the highest in BS20 and LM15. LM groups showed similar textural profiles to CON. The addition of potato flour togaraetteokincreased the turbidity of soup (tteokguk), but the fermentation significantly lowered its turbidity. During storage for 24 h,garaetteokwith fermented potato flour showed the inhibition of starch retrogradation. All scores of LM15 and LM20 were better than other potatogaraetteoksand similar to those of CON with the exception of color acceptance. Consequently,garaetteok-added potato flour fermented withL. mesenteroideswas the most preferable in terms of texture, cooking, and sensory characteristics.

Levan-Producing Leuconostoc citreum Strain BD1707 and Its Growth in Tomato Juice Supplemented with Sucrose

A levan-producing strain, BD1707, was isolated from Tibetan kefir and identified as Leuconostoc citreum. The effects of carbon sources on the growth of L. citreum BD1707 and levan production in tomato juice were measured. The changes in pH, viable cell count, sugar content, and levan yield in the cultured tomato juice supplemented with 15% (wt/vol) sucrose were also assayed. L. citreum BD1707 could synthesize more than 28 g/liter of levan in the tomato juice-sucrose medium when cultured at 30°C for 96 h. Based on the monosaccharide composition, molecular mass distribution, Fourier transform infrared (FTIR) spectra, and nuclear magnetic resonance (NMR) spectra, the levan synthesized by L. citreum BD1707 was composed of a linear backbone consisting of consecutive β-(2→6) linked d-fructofuranosyl units, with an estimated average molecular mass of 4.3 × 10(6) Da.

Dextran synthesized by Leuconostoc mesenteroides BD1710 in tomato juice supplemented with sucrose

The characteristics of the growth of Leuconostoc mesenteroides BD1710 and the synthesis of dextran in tomato juice supplemented with 15% sucrose were assayed. L. mesenteroides BD1710 could synthesize approximately 32 g L(-1) dextran in the tomato-juice-sucrose medium when cultured at 28 °C for 48 h, which was on the same level as the dextran yield in a chemically defined medium. The viscosity of the cultured tomato-juice-sucrose medium with various dextran contents was also measured. The results of the monosaccharide composition, molecular-weight distribution, Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance spectra (NMR) showed that the polysaccharide synthesized by L. mesenteroides BD1710 in the tomato-juice-sucrose medium was dextran with a peak molecular weight of 6.35 × 10(5)Da, a linear backbone composed of consecutive α-(1 → 6)-linked d-glucopyranosyl units and approximately 6% α-(1 → 3) branches.