Inhibiton Effect Of Protamine On Bacteria And Bacterial Biofilm And Prelimary Application Research

Protamine is a natural protein extrcted from fish spermary, non-toxic, having no harm and no side effects, which were proved by many toxicology experiments, its antibacterial activity contributes to potential application in the field of drug and food industry. Surimi and its products is a favorable way for effective use of the fresh fish, but due to their high moisture content, rich nutrient, they are susceptible to microbial contamination and spoilage, not only caused economic losses but also raised the food safety hazards. The addition of chemical preservatives can may cause security risks and adverse effects on the quality. so sereaching natural preservatives which not only have the ability of biocidal property but also improves the quality of food have been raised much concern. The object of this study is to reseach the antibacterial property of protamine and its effect on the formation of bacterial biofilm and the appilication to surimi and surimi gel in order to supply theroretical basis for the application of protamine in food.1. The inhibitory properties of protamine were tested, including the minimum inhibitory concentration (MIC) of several typical food pathogens, antibacterial rate and food ingredients’s effect on its antibacterial activity. The conclusions were as follows:the inhibitory effect on common Staphylococcus aureus was relatively better. The MIC was1.25X104g/mL. The antibacterial activity decreased when the strain has the ability of drug-resistance. The MIC was5.00X10g/mL. Effect of protamine on bacteria was soon, it could completely inhibit bacteria in a few minutes; when the protamine’s concentraion was higher, its antibacterial activity was hardly affected by food ingredients, when the concentration of protamine reduced to the minimum inhibitory concentration of the bacteria, sugars (including glucose and sucrose) in the food, sodium chloride and fat reduced the protamine the antibacterial activity to a certain extent,5%glucose,5%sucrose,1.5%fat decreased the antibacterial activity by36.8%,34.3%,38.5%. NaCl could also decrease the antibacterial activity of protamine, what’s more, NaCl could help the formation of bacteria biofilm.2. Establishing several different bacterial biofilm formation model of Staphylococcus aureus, different concentrations of protamine were added to the medium at different time to reaseach the effect of protamine on the biofilm formation. The results were as follows:Staphylococcus aureus could form biofilm when cultured in suitable conditions in PS board, test tubes(medium added glu) and cover slips at37℃, the ability of biofilm formation was related to many factors, such as the kind of strain, the supply of oxygen, the ingredients of medium. The greater amount of biofilm formed on the junction surface of the gas-liquid, indicating that the ability of biofilms formation was strong when adequate supply of oxygen was given, glucose helped bacteria biofilm formation; Adding the protamine before the bacterial biofilm formation could better inhibit the formation of bacterial biofilms, adding protamine after the formation of bacterial biofilm of Staphylococcus aureus, the inhibitory effect of the biofilm was relatively poor, LB medium containing5.00×10-4g/mL protamine could’t kill all the bacteria in the biofilm on the silde which cultured for24h, cultured for another24h, there were still5.23LgCFU/g in the bioflim, howerer, when combined with EDTA, effect on bacterial biofilms was increased. The number of bacteria counts reduced to3.94LgCFU/g.3. Adding different concentrations of protamine to surimi and surimi gel to research the effect of protamine on preservation of them, the following were results:the0.0182%,0.0375%,0.075%protamine could extend the shelf life of fresh surimi2days,2days and more than2days, but the effect was still to be improved, sterilization of surimi or increasing the concentration of protamine were needed. Protamine could extend the shelf life of surimi gel, surimi gel with no protamine spiol in the sixth day, surimi gel added0.075%and0.15%protamine would’t spoil after being conversered for12days. surimi gel added0.15%protamine didn’t exist staphylococcus aureus after being conserved for12days. The pH value of surimi gel added protamine rised relatively slower, being conserved for12days, the pH value of the control group rises by0.77, while surimi gel added0.15%protamine only rises0.43. Protamine(0.075%) increased the springness of surimi gel by0.085. Whiteness of surimi gel added protamine(0.15%) was3.36higher than the control group. The initial water holding capacity decreased when adding protamine to surimi gel, but in the sixth day, surimi gel added0.075%protamine’s water holding capacity was higher than the control group. What’s more, bacterial in surimi gel had the ability of biofilm formation when stored in4℃, surimi gel added protamine had less the ability.