Effects Of Different Bases On Freeze Drying Survival Rate Of Lactiplantibacillus Plantarum LIP-1 And Its Mechanism

In order to investigate the effect of adding trace growth factors to the culture medium on the freeze drying survival rate of strains,this study took 4 strains of Lactiplantibacillus plantarum as the research object,by adding different concentrations of adenine,uracil and hypoxanthine to the culture medium,we explored their effect on the freeze drying survival rate of Lactiplantibacillus plantarum,and took Lactiplantibacillus plantarum LIP-1 as the representative to explore the internal mechanism of different bases affecting the freeze drying survival rate of strains.The results showed that compared with the blank control group without base,the freeze drying survival rate of four strains of Lactiplantibacillus plantarum could be significantly improved when 0.01 g/L adenine,0.05 g/L uracil and 0.03 g/L hypoxanthine were added to the culture medium respectively(P<0.05).In addition,0.01 g / L adenine and 0.05 g/L uracil could also increase the growth of four strains of Lactiplantibacillus plantarum(P<0.05).Represented by Lactiplantibacillus plantarum LIP-1,the mechanism was explored and found:(1)The addition of adenine can reduce the damage of cell membrane and DNA of Lactiplantibacillus plantarum LIP-1.Lactiplantibacillus plantarum LIP-1 can use adenine to synthesize a large amount of adenosine triphosphate(ATP).The increase of intracellular ATP content will feedback inhibit the glycolysis pathway,reduce the conversion of pyruvate to lactic acid and increase the conversion to acetyl Co A,which provides sufficient substrate for cell membrane fatty acid synthesis;The increase of ATP content can also enhance the activity of acyl Co A thioesterase.Under the catalysis of acyl Co A thioesterase,the saturated fatty acid of cell membrane is transformed into unsaturated fatty acid,which reduces the damage of cell membrane in the process of freeze drying.In addition,the reduction of pyruvate to lactic acid leads to the increase of intracellular p H value,alleviates the degree of acid stress,reduces the damage of DNA and improves the stability of DNA.(2)The addition of uracil reduced the damage of cell wall and cell membrane of Lactiplantibacillus plantarum LIP-1.The addition of uracil can promote Lactiplantibacillus plantarum LIP-1 to synthesize more uridine diphosphate(UDP),so as to increase the content of peptidoglycan and improve the stability of cell wall.At the same time,the addition of uracil inhibited the conversion of whey acid to uridine diphosphate and increased the content of orotic acid in cells.The strain used the antioxidant ability of orotic acid to reduce the oxidation degree of reactive oxygen species to unsaturated fatty acids in cell membrane,and then reduce the damage degree of cell membrane.(3)Adding hypoxanthine can increase the biofilm production of Lactiplantibacillus plantarum LIP-1 and reduce the degree of DNA damage.The addition of hypoxanthine can promote Lactiplantibacillus plantarum LIP-1 to produce more guanosine tetraphosphate(pp Gpp),so as to improve the production of biofilm.In addition,the addition of hypoxanthine also makes the strain intracellular the increase of γ-aminobutyric acid(GABA)content alleviated the degree of acid stress,reduced the damage of DNA and improved the stability of DNA.The results showed that Lactiplantibacillus plantarum LIP-1 alleviated the freeze drying damage and improved the freeze drying survival rate of the strain by metabolizing adenine,uracil and hypoxanthine.This study provides a new method and idea for improving the survival rate of freeze drying strains.