| People in Yanbian of Jilin Province have the habit of eating pickled cabbage,spicy cabbage and Korean pickles,which contain a large number of lactic acid bacteria resources.At present,the lactic acid bacteria(LAB)strains in China are mainly isolated from fermented dairy products in Inner Mongolia,Xinjiang,Qinghai,Tibet,Yunnan,etc.,while precious microbial resources contained in fermented pickles in Yanbian area are less developed.Exopolysaccharides(EPS)is the secondary metabolite of LAB and has a variety of biological functions.The beneficial functions of LAB to human health,including immune regulation,anti-oxidation,cholesterol lowering,blood pressure lowering,etc.Are also partly due to the EPS produced by LAB.Studies have confirmed that LAB EPS is with antioxidant,immune regulation,anti-tumor,antibacterial function,etc.,among which antioxidant function is the basis of other functions and also the most important function for in-depth study.This study collected more than 300 samples of pickled cabbage,spicy cabbage and Korean pickles from different shops in Yanji city.After morphological observation,biochemical reaction and 16S r DNA sequencing,more than 160 strains of LAB were isolated from the samples,and 2 strains with high EPS production were screened.It was identified as Lactobacillus plantarum by 16S r DNA sequence analysis and named as Lactobacillus plantarum A76 and A114 respectively.The purified polysaccharide components were obtained by DEAE-52 cellulose column and Sepharose CL-6B gel column,and their structure and antioxidant activity were analyzed.The main results were shown as follows:(1)L.plantarum A76 and A114 with high EPS production were screened by colony mucilage method.The crude EPS yield was 1.569g/L for L.plantarum A76and 1.763g/L for L.plantarum A114.EPS LP-A1,LP-A2,LP-A3,LP-A4 from L.plantarum A76 and EPS LP-B1,LP-B2,LP-B3,LP-B4 from L.plantarum A114 were purified by DEAE-52 cellulose column and Sepharose CL-6B gel column,respectively.(1)The EPS produced by A76 and A114 were extracted,and A76 was separated and purified by DEAE-52 ion exchange column chromatography to obtain polysaccharide components,which were named LP-A1,LP-A2,LP-A3,LP-A4 and A114 were separated and purified by DEAE-52 ion exchange column chromatography to obtain polysaccharide fractions,which were named as LP-B1,LP-B2,LP-B3 and LP-B4.(2)The molecular weight and monosaccharide composition of the purified EPS were detected by gel permeation chromatography and gas chromatography,and the structure of the EPS purified from L.plantarum A76 and L.plantarum A114 were studied.The average molecular weight of EPS LP-A1 was 3.332×105 Da and weight-average molecular weight was 1.206×10~6Da,and the main components were mannose and a small amount of galactose.The average molecular weight of EPS LP-A2 was 1.777×10~4Da and weight-average molecular weight was 1.233×10~5Da.The main components of EPS LP-A2 were fucose,xylose,mannose and a small amount of glucuronic acid.The average molecular weight of EPS LP-A3 was2.040×10~5Da and weight-average molecular weight was 4.639×10~5Da,and its main components were only mannose.The average molecular weight of EPS LP-A4 was1.339×10~4Da and weight-average molecular weight was 4.363×10~4Da,and the main components were xylose,mannose and glucose.The number average molecular weight of EPS LP-B1 was 2.620×10~5Da and the weight-average molecular weight is 3.897×10~5Da,and the main components were mannose and galactose.The average molecular weight of LP-B2 was 3.650×106 Da and the weight-average molecular weight was 4.218×106 Da,the main components were mannose,xylose and galactose,the average molecular weight of EPS LP-B3 was3.650×10~6Da,the weight-average molecular weight was 4.218×10~6Da,and the main components were fucose,mannose,glucose,galactose and glucuronic acid.(3)L.plantarum A76 crude EPS and its purified components LP-A1,LP-A2,LP-A3,and L.plantarum A114 crude EPS were with strong scavenging ability of·OH radical and ABTS radical.L.plantarum A76 and its purified components LP-A1,LP-A2,LP-A3,LP-A4,as well as L.plantarum A114 and its purified components LP-B1,LP-B2,and LP-B3 had the ability to inhibit DPPH free radical.Therefore,all above EPS had certain antioxidant ability in vitro.(4)The EPS from L.plantarum A76 and A114(125μg/m L)promoted the proliferation of RAW264.7 macrophages and protected against LPS stimulation.Some purified EPS components could protect RAW264.7 macrophages and increase SOD activity under LPS stimulation.In conclusion,both L.plantarum A76 and A114 have the ability to produce EPS at high yield,and part of the purified EPS components have good in vitro antioxidant activity,which can promote the proliferation of RAW264.7 macrophages at a certain concentration.Furthermore.they have a certain protective effect on RAW264.7macrophages under LPS stimulation.This study provided a theoretical basis for further exploring the antioxidant function of EPS of LAB and fully utilizing and developing LAB resources in northeast China. |
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