Characterization And Biological Activities Of The Exopolysaccharide From Lactobacillus Plantarum JLAU103

Lactobacillus exopolysaccharide(EPS)is a high molecular polymer produced by Lactobacillus during the metabolism.There are a lot of Lactobacillus producing EPS,such as Lactobacillus casei,Lactobacillus rhamnosus,Lactobacillus acidophilus and Lactobacillus plantarum.Lactobacillus plantarumis widely distributed in nature.EPS produced by Lactobacillus plantarum can be used as natural nutritional factors in functional foods due to its biological activities and non-toxic side effects.Based on this,Lactobacillus plantarum with high EPS production was isolated and screened from the traditional self-fermented food Inner Mongolia tofu.The purification,characterization and biological activities(antioxidant and immunomodulatory activities)of EPS were studied and the specific experimental results were as follows:An EPS-producing Lactobacilli strain named JLAU103 was screened by combining with the appearance of “ropy” strand colony formed on the screening plate and the polysaccharide production,whichcrude EPS production was about 75.58 mg/L by phenol-sulfuric acid method.The strain JLAU103 was identified as Lactobacillus plantarum according to morphological and 16 S rDNA tests.An acidic EPS designated as EPS103 was obtainedby ethanol precipitation,DEAE-Sepharose Fast Flow ion-exchange chromatography column and Sepharose CL-6B gel filtration chromatography column.By high performance volume exclusion chromatography(HPSEC)and gas chromatography-mass spectrometry(GC-MS),EPS103 had a relatively lower molecular weight of 12.4 KDa and was consisted of arabinose,rhamnose,fucose,xylose,mannose,fructose,galactose,and glucose in an approximate molar ratio of 4.05: 6.04: 6.29: 5.22: 1.47: 5.21: 2.24: 1.83.A specific spectrogram of acidic polysaccharide with carboxyl and hydroxyl groups was obtained by FT-IR analysis,and both ?-and ?-type configurations were presented in EPS103 based on the NMR spectroscopy.Microstructural analysis of EPS103 demonstrated a smooth,glittering and compact interiorcube structure,and presence of many homogeneous rodshaped lumps.In addition,TG-DSC analysis showed that EPS103 had good thermal stability.Comprehensive study of in vitro antioxidant activity indicated that EPS103 hadstrong scavenging abilities against hydroxyl,ABTS,and DPPH radicals,with the maximum of 80.4%,65.5%,and 60.5%,respectively at 10 mg/mL concentration.Furthermore,EPS103 also showed strong ferrous ions chelating activity and oxygen radical absorbance capacity.These results together indicated that the EPS103 isolated from L.plantarum JLAU103 has great potential for use as a natural antioxidant in foods industry.The in vitro immunomodulatory activity of EPS103 in RAW 264.7 macrophages with or without lipopolysaccharide(LPS)activation wasalso investigated.The results showed that EPS103 possessed dual in vitro immunomodulatory actions.EPS103 could significantly enhance the phagocytic activity of RAW264.7 macrophages and promote the secretions of IL-6,TNF-?,and NO in RAW264.7 macrophages.At the same time,EPS103 could also significantly inhibit the production of IL-6,TNF-?,PGE2,and NO,as well as the expression of IL-6,TNF-?,COX-2,and iNOS in RAW264.7 macrophages activated by LPS.Moreover,the phosphorylation and degration of I?B-? were also inhibited by EPS103 in LPS activated RAW264.7 macrophages,which suggested that EPS103 exerted immunomodulatory activity through inhibiting the activation of NF-?B signaling pathway.In this study,the characterization,in vitro antioxidant and immunoregulatory activities of the EPS from Lactobacillus plantarum JLAU103 were preliminarily explored.The results of the present study will provide a reliable theoretical basis for its application in dairy products and a reference for the high-value utilization of Lactobacillus resources in China.