Study On Antimicrobial Activity Of Marine Sulfate Polysaccharide And Its Application In Meat Preservation

In recent years,people pursue more safe and effective natural compounds used in the food industry as safety incidents caused by food safety incidents occur so frequently.Algae contain a large amount of natural sulfate polysaccharide,which has extensive biological activities such as anti-coagulant,anti-tumour,anti-viral,anti-gastrelcosis and anti-inflammatory and so on.However,there are only few reports about their antibacterial activity and antibacterial mechanism.In our study,the preparation process of low molecular weight fucoidan and it antibacterial activity,antibacterial mechanism and also the application in meat preservation were studied.The conclusions we obtained were as follows:Section 1:For observing of the rheological mechanics difference,the characteristic viscous parameters of standard dextran and dextran sulfate were detected;and then,the improved Mark-Houwink-Sakurada?MHS?model and conventional column chromatography technique were employed to analyze the disruptive effects of sulphating on detecting molecular weight of polysaccharide.The results show that the dextran and dextran sufate have different fluid mechanics properties.The slope of the relation of C and?_sp/C for dextran is positive,comparing with the negative slope for dextran sulfate.According to the improve MHS model,there also are significant different in constant in mathematical formulas for the two polysaccharide.Based on results of the column chromatography technique,the detected molecular weight of dextran sulfate is far greater than the real value if the dextran is used as standard substance.Therefore,sulphating can change the rheological behavior of polysaccharide,and,as a result,the molecular weight of sulphated polysaccharide will be misjudged if dextran is used as standard substance.Section 2:Take the viscosity and antibacterial activity of polysaccharides as the evaluation index to determine the optimum conditions degraded by the infrared radiation and the optimal degradation conditions by high pressure:fucoidan with 30%of the amount of water degraded at121?for 40 minutes and during the process of degradation would not cause sulfate shedding.Furthermore,we found out that air-blast drying and infrared drying were not suitable for the drying of degradation products.In this experiment,the antibacterial activity of fucoidan against G-?E.coli?,G+?S.aure?and lactobacillus bacteria was detected by liquid turbidity method and plate smearing method.Degradation products were found to have inhibitory effect on both strains and the inhibitory effect of S.aure was better than that of E.coli with gradually increased at the concentration 4 mg/ml.But it should be noted that the degradation products also had a inhibitory effect on lactic acid bacteria,which antibacterial activity was relatively weak as it began to show obviously at the concentration more than 10 mg/ml.Section 3:Molecular weight and sulfate content are two important factors that influence the antibacterial activity of fucoidan.Five fractions?<6 kDa,6-20 kDa,20-50 kDa,50-80 kDa,>80kDa?were isolated by different ultrafiltration membrane and two fractions?M₁,M₂?were purified by anion exchange chromatography on DEAE-Cellulose 52 column.All these components were used in the bactericidal experiment.The results showed that:for E.coli,the molecular weight less than 6 kDa had the best inhibitoey effect with a MIC of 8 mg/ml and a MBC of 12.5 mg/ml;in contrast,the molecular weight of 6-20 kDa had the worst effect with a MIC of 12.5 mg/ml and a MBC of 25 mg/ml;For S.aure,the antibacterial activity of fucoidan enhanced with the decrease of molecular weight,the molecular weight less than 6 kDa was also the best with a MIC of 6.25 mg/ml and a MBC of 10 mg/ml and other components were similar except for one?>80 kDa?with a MBC of 25 mg/ml;at the same time,the higher the content of sulfate group,the better the antibacterial effect.Furthermore,we also found that fucoidan could destroy the cell membrane of bacteria,as evidenced by the nucleic acid absorption at 260 nm,fluorescence spectrum and SEM,which lead to the leakage of intracellular substances and affect the conformation of the membrane proteins.FT-IR spectroscopy analysis confirmed that fucoidan have effect on cell membrane phospholipids,proteins,fatty acids and may cause damage to DNA and RNA.Section 4:According to the film forming properties of sodium alginate and the antibacterial activity of fucoidan,the optimum mixture ratio was determined of 7:3?w/w?,8:2?w/w?.Then,the best compound solutions were applied to the preservation of pork.It found that complex?7:3?used in the chilled meat has better preservation effect as it could keep the quality indexes such as pH value,juice leakage rate,total bacteria count and sensory score in a normal range,at which the shelf life was prolonged by 7 d or so.