Effect Of Lactic Acid Bacteria Zinc On Growth And Reproduction Development Of Rats And Study On Zinc Enrichment Process

Zinc is a trace element necessary to maintain normal growth and reproduction development of the body,and zinc deficiency is a common nutritional deficiency,especially in young children who are at high risk of zinc deficiency during growth and development.Zinc deficiency will casue growth retardation,reproduction system dysplasia and other symptoms.Currently,zinc supplements mainly consist of zinc citrate and zinc gluconate.Microbial enrichment conversion of inorganic zinc is a new composite organic zinc form.Some active lactic acid bacteria（LAB）strains such as Bifidobacterium and Lactobacillus that are beneficial to host health have the potential to enrich and transform metal ions.In this study,strains with high zinc enrichment ability were screened and their organic zinc content was analyzed;then,the effects of different strains of LAB zinc and different doses of Bifidobacterium longum zinc on the growth and reproduction health of rats were investigated by animal experiments;finally,the zinc-enriched process was optimized.The main research contents are as follows:First,70 strains of Bifidobacterium and Lactobacillus were inoculated into a liquid medium containing inorganic zinc,and the bacterial sludge was collected and washed with distilled water and then lyophilized to prepare zinc-enriched bacteria powder.The total zinc content was measured directly by flame atomic absorption spectrometry,and the organic zinc content was measured after EDTA rinsing.The results showed that the zinc enrichment ability of different strains cultured in zinc-containing medium was quite different,and the zinc enrichment ability of Bifidobacterium was generally better than that of Lactobacillus.Finally,three Bifidobacterium with strong zinc enrichment ability were screened out,namely Bifidobacterium longum CCFM1195（total zinc content was 3.40 mg/g,organic zinc accounted for 96.47%）,Bifidobacterium animalis CCFM1230（total zinc content was 2.94 mg/g,organic zinc accounted for 95.26%）and Bifidobacterium breve CCFM1198（total zinc content was 2.26mg/g,organic zinc accounted for 94.47%）.Second,the zinc-deficiency rat pups model was established,and the effects of Bifidobacterium zinc of different strains（Bifidobacterium longum CCFM1195,Bifidobacterium animalis CCFM1230 and Bifidobacterium breve CCFM1198）on the growth and reproduction development of rats were investigated by the gavage with normal daily zinc intake.Inorganic zinc（Zn O）and Bifidobacterium+Zn O were used as control groups.The results indicated that zinc deficiency significantly affect the growth and reproduction development of rat pups.All the three kinds of Bifidobacterium zinc could be better absorbed and utilized in the body,and improved health status.The recovery ability of ALP activity,serum IGF-1 level,testosterone level and testicular tissue morphology was better than the corresponding Bifidobacterium+Zn O and Zn O,among which Bifidobacterium longum CCFM1195 zinc had the best effect.An in-depth study was conducted to evaluate the quantitative-effect relationship among the effects of Zn O,Bifidobacterium longum CCFM1195+Zn O,active Bifidobacterium longum CCFM1195 zinc and inactive Bifidobacterium longum CCFM1195 zinc on growth,development and reproductive health in rats were evaluated at low,medium and high doses.The results showed that Bifidobacterium longum CCFM1195 had the best effect on health improvement,followed by Bifidobacterium longum CCFM1195+Zn O,and Zn O was the worst,and this phenomenon was most significant at low dose.Due to the biological activity of Bifidobacterium longum CCFM1195,active Bifidobacterium longum CCFM1195 zinc was more advantageous than inactivated Bifidobacterium longum CCFM1195 zinc in terms of the absorption and utilization and recovery of physiological indicators of the body.Gut microbiota analysis showed that significant differences were observed in the microbiome of the model group and the zinc-treated groups.Supplementation of Zn O alone had no significant effect on microbial abundance and diversity,but supplementation with Bifidobacterium longum CCFM1195 significantly increased the diversity of gut microbiota and played a key role in regulating the balance of Lactobacillus and Blautia.Finally,the zinc absorption pharmacokinetics of Zn O,Bifidobacterium longum CCFM1195+Zn O and Bifidobacterium longum CCFM1195 zinc were analyzed.The results indicated that Zn O was rapidly excreted through absorption and metabolism cycles in the body and was poorly bioavailable.After enriched by bacteria,zinc combined with the bacterial structure in an organic form to reach the digestive tract,which was slowly released and absorbed after the bacterial cells in the intestine died and cracked,so that the body could maintain a high zinc level for a long time.Finally,the optimization of the zinc enrichment process of Bifidobacterium longum CCFM1195 was investigated in terms of the organic zinc content and the concentration of the bacteria.The nitrogen source,growth-limiting trace elements,carbon-nitrogen ratio,temperature,surface activity and the effect on both of these were studied.The results showed that the nitrogen source had the greatest influence on the zinc content of zinc-enriched Bifidobacterium longum CCFM1195;Tween 20 was more favorable for the enrichment of zinc by the bacteria.The most suitable zinc enrichment process was finally determined as:culture formula:glucose 20 g/L,fish bone peptone FP351 10 g/L,anhydrous sodium acetate 2 g/L,ammonium citrate dibasic 2 g/L,K₂HPO₄ 2 g/L,Mg SO₄·7H₂O 0.2 g/L,Tween 20 1 m L/L,L-cysteine 1 g/L.The initial concentration of Zn²⁺（Zn SO₄）in the medium was 200 mg/L,the inoculum was 2%,the culture temperature was 37°C,and the incubation time was 18 h.The final culture concentration of Zn-enriched Bifidobacterium longum CCFM1195 OD₆₀₀ was 0.52,the zinc content of the lyophilized bacteria powder could reach up to 84.2 mg/g.