Study On The Degradation Of N-Glycolylneuraminic Acid In Pork Based On Lactic Acid Bacteria Fermentation

N-glycolylneuraminic acid?Neu5Gc?enters the human body through red meat and its processed products.Neu5Gc causes immune inflammation,which promotes tumor growth and causes various disease problems.Fermented red meat products are traditional processed meat products.It is widely loved by consumers,and its safety is also receiving much attention.Lactic acid bacteria are the most important dominant strains in fermented red meat products.Lactic acid bacteria have powerful functional properties that can break down carbohydrates to produce lactic acid and lower the pH of red meat.Studies have shown that Neu5Gc is a 9-carbon skeleton of acidic sugars that can be used as a carbon source by bacteria,and structural instability under acidic conditions is easily destroyed by strong acids.The research on the degradation of Neu5Gc by lactic acid bacteria fermented pork and the fermentation control methods can provide a theoretical basis for the safety value of fermented meat products.In view of this,the degradation of N-glycolylneuraminic acid in pork based on lactic acid bacteria fermentation was carried out.?1?Establishment of Neu5Gc by high performance liquid chromatography with fluorescence detection method for fermented red meat productsThe release of Neu5Gc in the sample was confirmed by 2 mol/L glacial acetic acid solution,DMB was used as a derivatization reagent,and Agilent ZORBAX Eclipse XDB-C18 column?150 mm×4.6 mm×5?m?,a mixture of 80%ultra pure water and20%methanol as mobile phase,flow rate of 0.9 mL/min,fluorescence detector excitation wavelength 373 nm,emission wavelength 448 nm,etc.The results showed that the proposed method showed a good linearity between the ratio of Neu5Gc peak area and the mass concentration of Neu5Gc in the range of 25⁴00?mol/L,R²=0.99941.The recovery of spiked samples was between 96.4%⁹9.07%;The precision expressed as relative standard deviation?RSD?was 1.2%,the repeatability RSD was1.5%;the instrumental had a limit of detection?LOD?of 0.001?mol/L,and the limit of quantitation?LOQ?was 0.003?mol/L.The Neu5Gc content of fermented red meat samples was detected to be in the range of 9.59²0.08?g/g,with significant differences existing among these samples?P<0.05?.The method can effectively separate the target peaks of Neu5Gc?resolution R>1.5?with simple operation,good repeatability,high sensitivity and precision,which can be widely used for the determination of Neu5Gc in fermented red meat products.?2?Study on degradation characteristics of Neu5Gc degraded by lactic acid bacteriaA simple fermentation system was established to study the degradation characteristics of Neu5Gc by GDM1.919,GIM1.774,G1M11.294 and GDM1.895under different culture conditions such as pH,air content and inoculum size.The experimental results showed that there was no significant difference in the degradation of Neu5Gc under different inoculum size,except GIM1.774.The pH had a significant effect on the degradation of Neu5Gc by lactic acid bacteria.The degradation rate of Neu5Gc increased first and then decreased with the decrease of pH value in the medium.The oxygen-controlled fermentation showed that the degradation rate of Neu5Gc was the highest when the air content was 2 to 3 times the volume of the fermentation liquid.The first-order kinetic equation was used to linearly fit the residual concentration of Neu5Gc in the fermentation time of four strains of lactic acid bacteria every 12 h.By comparing the degradation rate k,the degrading rate of GDM1.919 had the strongest degradation rate,k=0.041.t_1/2=6.08 h.?3?Application and molecular mechanism of GDM1.919 in fermented pork productsGDM1.919 was inoculated into pork as a starter for fermentation,and natural fermentation was used as a control group.The contents of Neu5Gc and Neu5Ac were dynamically monitored to study the effect of reducing the immunogenicity of Neu5Gc during the fermentation of lactic acid bacteria.The experiment proves that the content of Neu5Gc decreased gradually with the increase of fermentation time,and the decrease trend of the experimental group was significantly higher than that of the control group?P<0.05?.The content of Neu5Gc in the experimental group and the control group showed an upward trend at 12h and 24h,respectively.However,with the decrease of water activity,the specific gravity of Neu5Gc increases with the same mass,which increases the detection content of Neu5Gc.However,the content of Neu5Gc in the experimental group was significantly lower than that in the control group at each time point?P<0.05?.which has practical significance for reducing the immunogenicity of Neu5Gc in fermented red meat products.On the whole,the content of Neu5Gc after fermentation is still lower than that of Neu5Gc in raw materials,which has practical significance for reducing the risk of Neu5Gc immunogenicity in fermented red meat products.The analysis of the intermolecular interactions of the complexes produced by the interaction of ethanol and lactic acid with all hydroxyl groups of Neu5Gc show that lactic acid is more reactive with Neu5Gc than ethanol,and the lowest binding energy in solvent is respectively It is-44.18 and-79.30 kcal/mol.Independent density gradient theory analysis show that ethanol and Neu5Gc can produce seven intermolecular hydrogen bonds,and lactic acid and Neu5Gc can produce fifteen intermolecular hydrogen bonds.The molecular force field energy decomposition show that the binding process is dominated by electrostatic interaction,in which the electrostatic interaction of ethanol-Neu5Gc interaction is-305.51 kJ/mol,and the electrostatic interaction of lactic acid-Neu5Gc complex is-538.74 kJ/mol.