| At present,the livestock and poultry industry advocates the concept of green,healthy,non-polluting development,microecological agents with its residue-free,non-toxic,nonresistant advantages gradually become a feed additive to replace antibiotics.Many trials and studies have shown that lactic acid bacteria can not only contribute to the stability of the livestock ecosystem,but also improve the antioxidant capacity of the body,reduce the production of PSE(pale,soft,exudative)meat,while lactic acid bacteria and their metabolites can also reduce the generation of harmful metabolites such as amines and hydrogen sulfide in the intestinal tract,reduce the off-flavors of livestock and poultry meat,thus improving the flavor of meat,which is of great significance to the growth and reproduction of livestock and poultry.As a healthy,efficient and environmentally friendly green disinfectant,hypochlorite is also favored by the livestock and poultry industry.Low-quality concentration of slightly acidic hypochlorite water can replace ordinary water mixed into powdered feed,and can also be directly used as drinking water.However,because it is bactericidal,while killing harmful bacteria in the body’s intestinal tract,it can also negatively affect beneficial bacteria to a certain extent.In this study,Lactobacillus strains that can tolerate a certain mass concentration of hypochlorite were screened and their ability to act as microecological agents was investigated,and finally,the tolerant strains were compared with the sensitive strains to analyze their tolerance mechanisms.The results were as follows:(1)Six traditional natural fermentation products were collected from Inner Mongolia pastoral areas.Eight suspected Lactobacillus strains were isolated and identified by morphology,physiology,biochemistry and 16 S r DNA gene fragment sequence analysis methods for species identification.The identification showed that MBH1-1 and MBH1-2were Lactobacillus fermentum;MBH2-1,MBH5-1 and MBH5-2 were Lactobacillus plantarum;MBH3-1,MBH3-2 and MBH3-3 were Lactobacillus paracasei.The screening test for eight strains of bacteria to tolerate non-electrolytic slightly acidic hypochlorite showed that MBH1-1 and MBH3-2 were able to tolerate hypochlorite at a mass concentration of 20 mg/L at a tolerated hypochlorite reaction time of 2 h;MBH2-1,MBH3-3 and MBH5-1 had the ability to tolerate a mass concentration of 10 mg/L.(2)Evaluation of the probiotic properties of five strains of hypochlorite tolerant.The logarithmic phase of each strain was determined after growth characteristic tests.After the tests of acid tolerance,bile salt tolerance,simulated artificial gastrointestinal fluid tolerance,hydrophobicity,self-consolidation ability and antioxidant ability,a strain with excellent ability to tolerate hypochlorite and meet the requirements as a microecological preparation was finally identified.The results showed that Lactobacillus paracasei MBH3-2 could survive in acidic(p H 2.0,2.5,3.0),bile salt and simulated artificial gastrointestinal fluid environment;the hydrophobicity reached 62.12%;the self-consolidation ability reached97.29% at 2 h;it has certain antioxidant ability.Finally,the hypochlorite tolerance effect of strain MBH3-2 was evaluated,and the survival rate could be maintained above 53.71%under the treatment condition of 300 min.(3)Comparative analysis of tolerant and sensitive strains.The tolerant strain MBH3-2and the sensitive strain MBH3-1 were treated with hypochlorite,and the enzyme activity,SOD activity and ATP content of ?-galactosidase were measured separately,and it was found that the tolerant strain could maintain a higher level of enzyme activity and ATP content than the sensitive strain.The analysis of the fatty acid composition of the cell membrane of the two strains showed that the proportion of saturated fatty acids in the tolerant strain was higher than that of the sensitive strain,which could better maintain the integrity of the cells. |
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