Optimization Of Production Process Of Selenium-Enriched Yeast And The Anti-PCV2Activity Of Zymosan

Selenium is an essential trace element in human and animal, it could improve immunity, eliminate free radicals, inhibit lipid peroxidation and have other biological functions. Zymosan is the main component of the yeast cell wall, accounting for about80%of the dry weight of the cell wall. Zymosan can not only improve immunity, anti-tumor, anti-virus as well as selenium, but also has the biological functions of adsorption of toxins, anti-radiation. Selenium-enriched yeast not only has lots of organic selenium (compared with inorganic selenium, it has lower toxicity, higher utilization and lower environmental pollution, etc.), but also has a lot of zymosan. As feed additives, selenium-enriched yeast can prevent diseases maximize.The optimum fermentation conditions were obtained by the shake-flask experiment, then, cells were cultivated in fermenter with the optimum fermentation conditions, optimize the feed rate of selenium and nutrition, and produce the low-cost selenium-enriched yeast ultimately. And give a study on anti-PCV2of zymosan and its mechanism, to provide a theory for application of selenium-enriched yeast.Experiment1. The shake-flask experiment of production of selenium-enriched yeast Optimize the medium and pH by the shake-flask experiment and observe the effect of adding selenium and nutrition in batches on production of selenium-enriched yeast. The results showed that the optimum medium formulation is glucose90g/L, urea3g/L, corn steep powder11g/L. Optimum initial pH is5. Compared with single-dose addition, addition in batches can get higher selenium biomass, and addition in batch at5h,9h,13h could abtain the most biomass. Biomass can be further improved with adding nutrition in batches at the late logarithmic growth phase, biomass was9.8g/L, selenium content closed to1700μg/g, and selenium conversion rate was72.1%finally.Experiment2. The fermenter experiment of production of selenium-enriched yeast Cells were cultivated in fermenter with the feed rate of selenium and nutrition under the optimum fermentation conditions obtained by the shake-flask experiment. Supplementary medium was fed by different constant rate firstly. The final biomass had reached a higher value after cultivating with three different constant feed rate, but selenium content and was still low as well as selenium conversion rate, so cultivate cells by changing feed rate under different selenium concentrations, results showed that under moderate concentrations of selenium, the biomass was43.76g/L, selenium content was1272.45μg/g, the conversion rate of66.8%selenium.Experiment3. Preliminary study of the anti-PC V2of zymosan and its mechanism Get the maximum safe concentration of zymosan on PK-15cells by MTT, then, study effect of inhibition and direct killing of zymosan on PCV2, and the effect of zymosan on PCV2adherent to cells. The results showed that the maximum safe concentration of zymosan on PK-15was125μg/mL, zymosan had the biological function of anti-PCV2on PK-15, and its mechanism was the inhibition of PCV2adherent to cells and the direct killing effect.