Study On The Ruminal Degradation Characteristics Of Fermented Vinegar Residues By N. Sitophila And The Antioxidant Activity Of Carotenoids From The Fermentation

In order to convert the vinegar residues with large emissions and low nutritional value into high-nutrition functional feeds,a fermentation experiment of vinegar residues by N.sitophila was conducted,and the degradation characteristics of fermented vinegar residues in sheep rumen were studied in both vitro and vivo experiments.Then,a series of studies were conducted regarding the fermenting production process,extraction methods and antioxidant activities of carotenoids.1.Compared with those of the unfermented vinegar residues,the rumen degradation characteristics of the fermented vinegar residues were as follows: the cumulative gas production of both groups showed GP_24h<GP_48h<GP_72h?P<0.05?,while the fermented vinegar residues group showed significant increase in GP_24h,GP_48h,GP_72h and ME?P<0.05?,and significant decrease in CH₄ concentration,DMD,NDFD and ADFD?P<0.05?.There were no significant differences in VFA,NH₃-Nitrogen,protein nitrogen,urea nitrogen and total nitrogen?P>0.05?.2.Nylon bag technique was used to evaluate the nutritional value of vinegar residues before and after fermentation.The results showed that the effective degradability of DM in fermented vinegar residues was increased significantly from the unfermented ones?P<0.05?,while the effective degradability of CP and NDF was decreased significantly?P<0.05?,and the effective degradability of ADF showed no significant difference?P>0.05?.3.The Box-Behnken Design tests were used to optimize the technological conditions of vinegar residues fermented by N.sitophila,and the effects of several fermentation promoting factors on the carotenoids yield of N.sitophila were studied.The results showed that the optimal fermentation conditions were: inoculation amount at 8%?100 g of vinegar residues solid medium was added with 8 ml of spore suspension of N.sitophila with the spore suspension of concentration at 1.4×106 CFU/ml?,moisture content at 58%,and fermentation time at 85 h,under which the carotenoids yield could reach 68.03 mg/kg.The production of carotenoids was increased by adding tomato juice,orange peel,metal ions(Mg²⁺?Ca²⁺?Zn²⁺?Fe²⁺?K⁺)and vitamins?VB1?VB2?VC?in the medium.The orange peel showed the most significant effect among these fermentation promotors.When 4.2 mg orange peel was added to 1 kg vinegar residues medium,the carotenoids production reached 119.85 mg/kg,which was more than 1.79 times as large as the production of the control group.4.The methods of breaking the cell wall of N.sitophila spores and the extracting solvents for carotenoids were both screened by single factor tests.Based on the results of the single factor tests,the Box-Behnken design?BBD?was used to optimize the extraction process of carotenoids in N.sitophila,with lactic acid concentration,lactic acid dosage,oscillating time and boiling water bath time as independent variables and the extraction yield of carotenoids as dependent variable.The results showed that the method of lactic acid-heat assisted was the best to break the cell wall,and the mixed solvent of ethyl acetate and absolute ethanol?2:1?was the most suitable solvent for the extraction of carotenoids.The optimum combination of the parameters of the broken cell wall of the N.sitophila was: lactic acid concentration at 2.8 mol/L,lactic acid dosage at 14 ml/g,oscillating time at 20 min,and boiling water bath time at 8 min.Using the optimized process,the extraction yield of carotenoids was 793.75 mg/kg.5.The results of in vitro antioxidant test of carotenoids produced by N.sitophila showed that the antioxidant activity of carotenoids was positively correlated with the concentration of extract?5²00 ?g/ml?.Its scavenging ability against DPPH,superoxide radicals and hydroxyl radicals was significantly stronger than the ?-carotene,VC and VE at the same concentration?P<0.05?.In addition,carotenoids from N.sitophila fermentation also showed a certain inhibition ability on the oxidation of lipids and metal ion chelating.The above results indicated that the fermentation of N.sitophila not only improves the nutritional value of vinegar residues,but also produces carotenoids with strong antioxidant activity,which lay a foundation for the development of functional feeds of carotenoids from vinegar residues.