Screening of Calcium-enriched Lactic Acid Bacteria and the Effect of Culture Conditions on Calcium-enriched

In order to screen for lactic acid bacteria with strong calcium conversion and enrichment ability (for subsequent fermentation of fish bone paste), this paper studied the growth ability, acid production ability and calcium accumulation ability of seven lactic acid bacteria(Lactobacillus plantarum CY1-1, Lactobacillus plantarum Z7, Pediococcus pentosaceus DBY2-5-1, Lactobacillus casei D400, Lactobacillus oryzae DL10, Lactobacillus acidophilus DL12, Lactobacillus sake YP4-5) and their composite strains. The effects of calcium ion concentration, growth time, pH, and temperature on the calcium-enrichment capacity of the primary strains were studied, and the differences in the surface structure of the bacteria before and after the enrichment were observed by atomic force microscope, and the morphological changes of lactic acid bacteria and the mechanism of calcium absorption were studied. The results showed that lactic acid bacteria with the highest calcium enrichment were Lactobacillus plantarum CY1-1 and Lactobacillus plantarum Z7. The composite strains with the best enrichment ability were the combination of Lactobacillus plantarum CY1-1 and Lactobacillus acidophilus DL12, Lactobacillus plantarum Z7 and Lactobacillus sake YP4-5. Compared with the single strain, the calcium enrichment in those two composite strains increased by 6.76 and 21.69 mg/g, respectively. The enrichment ability in the stable phase was better than the logarithmic phase, the optimal concentration of calcium ion was 1.2 mg/mL, the optimal pH of Z7 was 6, Z7+YP4-5, CY1-1, and CY1-1+DL12 were 7.2, the optimal temperature of the Z7+YP4-5 group was 37 ℃, the remaining groups were 40 ℃. Atomic force microscopy observed significant differences in the cell surface structure before and after calcium enrichment by lactic acid bacteria. The above results showed that the single strain with the strongest calcium-accumulating ability was Lactobacillus plantarum CY1-1, and the composite strain were Z7+YP4-5; lactic acid bacteria could effectively adsorb calcium ions on the surface of the bacteria.