| Selenium is more common in the earth's crust,and it is particularly important for maintaining normal physiological metabolism and health level.However,the lack of selenium in soil is a global problem.It is difficult and costly to synthesize organic selenium artificially.Therefore,the preparation of organic selenium by biological methods has become a research hotspot.Bacillus natto is an edible probiotic that is non-pathogenic to the human body.It can convert sodium selenite to organic selenium.This study optimized the selenium-rich fermentation conditions of Bacillus natto and explored the effects of selenium-enriched Bacillus natto on senescence-related indicators,stress resistance and related antioxidant enzyme activities of C.elegans.It has a certain reference value in the research of high-efficiency and low-cost selenium sources,and provides a material basis and theoretical basis for further exploring the role of selenium-enriched Bacillus natto in human healthy aging.The results shown that:1.Through single factor experiments,it was determined that the addition of sodium selenite at the same time,and the mass concentration of sodium selenite at 10 ?g/ml were the optimal culture parameters.The response surface experiments determined that the effect of each culture condition on the conversion rate of organic selenium was: inoculum amount> initial p H value of the medium> culture time,the optimal culture parameters were: add strains while adding sodium selenite,and add 10?g/ml sodium selenite,the initial p H of the medium was 7.5,the culture time was 10 h,and the inoculation amount was 3.5%,The optimal conversion rate was 91.21%.2.When the treatment was applied for 5 d,the two selenium sources had no significant effect on the athletic ability of C.elegans(P>0.05),After 10 d of treatment,the movement ability of nematodes in the 40 ?g/ml sodium selenite group was significantly reduced(P<0.05),while the movement ability of the selenium-enriched Bacillus natto group was increasing with theincrease in concentration,18.26 ?g/ml concentration group increased significantly(P<0.05).The fecundity of C.elegans from the Bacillus natto group and sodium selenite group was not significantly different from the control group(P>0.05),9.13 ?g/ml and 18.26 ?g/ml selenium-enriched Bacillus natto groups have significantly increased fecundity(P<0.05,P<0.01).Compared with the control group,the average life of C.elegans in the40 ?g/ml sodium selenite group was significantly reduced by 15.05%(P<0.05),and the longest life was shortened by 20.27%(P<0.01),the average life of C.elegans in the 9.13 ?g/ml and 18.26 ?g/ml groups was 19.97% and27.91% longer than those in the control group(P<0.01).3.The average lifespan of C.elegans after treatment with different selenium-containing sodium selenite and selenium-enriched Bacillus natto is103.57 ± 9.56 min,76.67 ± 5.26 min,83.55 ± 7.43 min and 115 ± 10 min,124 ± 7.21 min,140.95 ± 12.15 min,which increased by 111.84%,56.82%,70.89% and 135.22%,153.63%,188.30% compared with the control group(P < 0.01).The average lifespan of C.elegans at 18.26 ?g/ml group was prolonged by 29.44% compared with the control group at 37?(P<0.01).After feeding 18.26 ?g/ml selenium-enriched Bacillus natto for 3 days,the activities of SOD and CAT enzymes were increased by 135.67% and 36.26%compared with the control group(P <0.01).All in all,selenium-enriched Bacillus natto has a certain protective effect on the nerve and muscle damage caused by aging of C.elegans,and it can also increase the fecundity of C.elegans.When the content of sodium selenite in the medium is low,there is no significant effect on the lifespan of C.elegans,long-term treatment with 40 ?g/ml sodium selenite has toxic effects on C.elegans,while selenium-enriched Bacillus natto has the effect of extending the life of C.elegans and the high concentration group has no toxic effect.It can also improve the oxidative stress and heat stress resistance of C.elegans and the activities of SOD and CAT enzymes of C.elegans,thereby improving the defense system of C.elegans.Therefore,selenium-enriched Bacillus natto has a significant effect on improving antioxidant capacity. |
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