Zhennai Yang

Antioxidant activity of Lactobacillus plantarum strains isolated from traditional Chinese fermented foods

Eleven Lactobacillus plantarum strains isolated from traditional Chinese fermented foods were investigated for their in vitro scavenging activity against hydroxyl and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals, and their resistance to hydrogen peroxide. L. plantarum C88 at a dose of 10(10) CFU/ml showed the highest hydroxyl radical and DPPH scavenging activities, with inhibition rates of 44.31% and 53.05%, respectively. Resistance of intact cells to hydrogen peroxide was also found in all strains. L. plantarum C88 was the most resistant strain against hydrogen peroxide. When L. plantarum C88 was administered to senescent mice suffering oxidative stress induced by d-galactose, the serum superoxide dismutase activity, the glutathione peroxidase activity and the total antioxidant capacity in liver increased significantly, while the level of malondialdehyde in liver decreased significantly. L. plantarum C88 isolated from traditional Chinese fermented dairy tofu could be considered as a potential antioxidant to be applied in functional foods.

Antioxidant activity of an exopolysaccharide isolated from Lactobacillus plantarum C88

A neutral exopolysaccharide (EPS), designated LPC-1, was isolated from the culture of Lactobacillus plantarum C88 and purified by ion-exchange and gel-permeation chromatography. LPC-1 had an average molecular weight of 1.15 × 10(6) Da, and it was composed of galactose and glucose with a molar ratio of 1:2. The antioxidant activity of LPC-1 was evaluated with the in vitro scavenging abilities on hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The results indicated that LPC-1 had good scavenging ability on hydroxyl radicals. Furthermore, the protective effect of LPC-1 on H(2)O(2)-induced Caco-2 cells oxidative injury was investigated. As results, LPC-1 inhibited the formation of malondialdehyde (MDA) and raised the activities of superoxide dismutase (SOD) and total antioxidant capacities (T-AOC) in a dose-dependent manner. These results demonstrate that the EPS from L. plantarum C88 has antioxidant effects that may involve scavenging of reactive oxygen species (ROS), up-regulation of enzymatic and non-enzymatic antioxidant activities, and reduction of lipid peroxidation.

Characterization of an exopolysaccharide produced by Lactobacillus plantarum YW11 isolated from Tibet Kefir

An exopolysaccharide (EPS)-producing strain YW11 isolated from Tibet Kefir was identified as Lactobacillus plantarum, and the strain was shown to produce 90 mgL(-1) of EPS when grown in a semi-defined medium. The molecular mass of the EPS was 1.1 × 10(5)Da. The EPS was composed of glucose and galactose in a molar ratio of 2.71:1, with possible presence of N-acetylated sugar residues in the polysaccharide as confirmed by NMR spectroscopy. Rheological studies showed that the EPS had higher viscosity in skim milk, at lower temperature, or at acidic pH. The viscous nature of the EPS was confirmed by observation with scanning electron microscopy that demonstrated a highly branched and porous structure of the polysaccharide. The atomic force microscopy of the EPS further revealed presence of many spherical lumps, facilitating binding with water in aqueous solution. The EPS had a higher degradation temperature (287.7°C), suggesting high thermal stability of the EPS.

Capsular and slime-polysaccharide production by Lactobacillus rhamnosus JAAS8 isolated from Chinese sauerkraut: Potential application in fermented milk products

Exopolysaccharides (EPSs) produced by lactic acid bacteria (LAB) play an important role in the improvement of the physical properties of fermented dairy products. To find EPS-producing LAB strains with potential industrial applications, a Lactobacillus rhamnosus strain, L. rhamnosus JAAS8, that is capable of producing two forms of EPS when grown in MRS broth or semi-defined medium with glucose as a carbon source was isolated and identified from Chinese sauerkraut. The capsular-polysaccharide (CPS) present surrounding the bacterial surface of L. rhamnosus JAAS8 was observed by both optical microscopy and transmission electron microscopy. The slime-polysaccharide (SPS) present in the growth medium was produced mainly during the exponential growth phase, while the CPS was produced only in fermentation. Monosaccharide analysis of the purified polysaccharide samples showed that the CPS was composed of galactose and N-acetylglucosamine in a molar ratio of 5:1, and the SPS was composed of galactose, glucose and N-acetylglucosamine in a molar ratio of 4:1:1. The use of L. rhamnosus JAAS8 could be considered for potential applications in the dairy industry to improve the rheological properties of fermented milk products by increasing their water-holding capacity and viscosity.

Characterization and bioactivities of an exopolysaccharide produced by Lactobacillus plantarum YW32.

The exopolysaccharide (EPS) produced by Lactobacillus plantarum YW32 was purified and characterized, and the in vitro bioactivities of the purified EPS were also evaluated. The EPS had a molecular weight of 1.03×10(5) Da, and it consisted of mannose, fructose, galactose and glucose in an approximate molar ratio of 8.2:1:4.1:4.2. Microstructural studies of the EPS demonstrated a web-like structure composed of compact ropes, and presence of many homogeneous rod-shaped lumps. The EPS also showed high thermal stability with a degradation temperature of 283.5°C. Furthermore, the EPS at a dose of 5mg/ml had strong scavenging abilities toward hydroxyl (77.5%) and superoxide radicals (66.5%). The EPS exhibited a concentration-dependent inhibitory effect on the formation of biofilms by several pathogenic bacteria, including Escherichia coli O157, Shigella flexneri CMCC (B), Staphylococcus aureus AC1 and Salmonella typhimurium S50333. In vitro antitumor assay of the EPS showed that it had good inhibitory activity against colon cancer HT-29 cells. These characteristics and bioactivities of the EPS would make it a promising candidate for use as a potential food adjunct in foods with healthy properties.