Effect of Calcium Ions on the Freeze-drying Resistance of Lactobacillus plantarum LIP-1

Taking Lactobacillus Plantarum LIP-1 as a research object, this article explored the growth and the freeze-drying resistance of the strain by adding different concentrations of calcium ions to the culture medium. To understand the mechanism of calcium ions on the freeze-drying resistance of strain, the morphology, cell wall of the bacteria, the structural integrity of cell membrane and the fatty acid composition of cell membrane were studied. The results showed the growth of the strain increased by 0.717×10⁹ CFU/mL and the survival rate increased by 21.52% (P<0.05), when 0.5 mmol/L calcium ions were added to the MRS medium, compared with the control group without calcium ions. Moreover, the length of Lactobacillus Plantarum LIP-1 becomed shorter, the damage to the cell wall and cell membrane of the strain was reduced, the content of unsaturated fatty acids in the cell membrane increased, and the U/S becomed larger. More importantly, the storage stability of the strain at room temperature was improved. We founded that the number of viable bacteria in the experimental group increased by 13.65 times compared with the control group (MRS) at the 8th week. Our result provides a theoretical reference for promoting the growth of bacteria and improving the freeze-drying resistance and storage stability of the strain by adding appropriate amount of calcium ions to the culture medium.