Study On The Optimization And Structure Of Expolysa-Charides Produced By Lactobacillus Plantarum12

Lactic acid bacteria exopolysaccharides(LAB EPSs)are kinds of long-chain biological macromolecules that are produced during the process of lactic acid bacteria.There are a large of researches have proved that some LAB EPSs have been applied in the pharmaceutical indus-try and food industry.Due to its antioxidant activity,antitumor effects and other physical activ-ities such as stabilizing,thickening or gelling properties,LAB EPSs have great research value and has become a research hotspot.This paper was to study on a EPS that inhibits the prolifer-ation of Caco-2 cells,to improve the culture conditions of this EPS,to isolate and purify the EPS and to investigate the physical and chemical properties and primary structure characteri-zation of the EPS.Firstly,the MTS method was used to measure the anticancer effect of EPSs produced by four strains of L.plantarum 12,L.plantarum 14,L.plantarum 32,and L.plantarum 37 pre-served in the laboratory.The result was founded that the EPS 12 had the highest inhibition rate to Caco-2 cells,reaching 42.1%.The inhibition rates of EPS 14,EPS 32 and EPS 37 on Caco-2 cell proliferation were 14.1%,32.6%and 22.5%respectively.Therefore,the EPS 12 was selected as a research object for subsequent experiments.Then the single factor and orthogonal experiment was used to optimize the culture condi-tions(type and concentration of carbon source,culture time,culture temperature,initial pH of the medium,amount of inoculum)of L.plantarum 12.From the test results,the best culture conditions for extracting EPS 12 were that carbon source was selected as sucrose,carbon source concentration was 4%,culture temperature was 37°C,culture time was 24 h,and initial pH was7.0.Then the crude EPS extracted and purified by a protein purification device.After purifica-tion with DEAE-Sepharose Fast Flow Ion Column,two components were separated and the two separated components were further purified by Sepharose CL-6B gel column to obtain two single components of EPS 12-1,EPS 12-2.The elution volume of the two components under the same conditions was determined using the standard curve of the elution volume and the relative molecular mass of the standard product on a Sepharose CL-6B gel column.After ex-periments,the molecular weights of these two components are both 3.58×10~5 Da.Finally,the purity of the two polysaccharides was tested and their physicochemical prop-erties and structure were studied.The UV scan results showed that there was no absorption peak at 260 nm and 280 nm for the two single components,indicating that both components contain no nucleic acids and proteins.The uronic acid content and the sulfate group content of the two components were measured by the metahydroxybiphenyl method and the turbidity measure-ment method of sulfuric acid.The measurement results showed that no uronic acid and sulfate groups were detected in EPS12-1.EPS12-2 The uronic acid content was 4.6%and the sulfate group content was 8.9%.The monosaccharide composition of EPS 12 was determined by high performance liquid chromatography and it was found that the monosaccharide type contained in EPS 12 was glucose.The infrared spectrum scanning analysis of the two components EPS12-1,EPS12-2 shows that there are typical characteristic absorption peaks of polysaccharides in both components EPS12-1,EPS12-2.