Study On Two Step Solid State Fermentation Of Soybean Meal And Its Partial Function

Soybean meal is a kind of byproduct which is obtained from extracting soybean oil by crushing soybeans.It has not only high nutritive value but also with balanced content of nutrient materials.So soybean meal is quite suitable for vegetable protein feed source for feeding animals.It has important significance to research on deep processing of soybean meal.Adopt microbial fermentation technology to degrade the anti-nutritional factor in the soybean meal and decompose soybean protein so as to improve the utility value.And then adopt acid extraction to extract soybean peptides from fermented soybean meal.Based on the soybean peptides with different concentration,make the research on antioxidant properties.Main results from the test are as follows:(1)Optimization research for technological conditions of soybean meal solid state fermentation with two steps:The first solid state fermentation is the mixing fermentation of bacillus subtilis and aspergillus niger.And then,take the mixing fermentation of saccharomyces cerevisiae and lactobacillus bulgaricus as the second solid state fermentation.Take the conversion rate of soybean peptides as the assessment index to determine the optimization parameter of soybean meal solid state fermentation with two steps.First fermentation:fermentation time:72 hours;liquid to material ratio:60%;fermentation temperature:34?;total inoculum concentration:10%;ratio of strains:3:1;the content of peptides and the conversion rate of obtained peptides were 21.11%and 52.01%.Second fermentation:fermentation time:48 hours;liquid to material ratio:40%;fermentation temperature:36?;total inoculum concentration:8%;ratio of strains:2:1;the content of peptides and the conversion rate of obtained peptides were 26.42%and 65.08%.Results show that solid state fermentation with two steps for multiple strains is more suitable for fermenting soybean meal,as the conversion rate of soybean with two-step fermentation is higher by 13.07%than that with one-step fermentation.(2)Research on changes of nutritive value before and after soybean meal fermentation:From the sense and appearance,the soybean meal after two-step fermentation has brown color and sour flavor,with PH of 4.2.On aspect of changes of nutrient components,the crude protein of fermented soybean meal is 45.74%,increasing by 5.14%compared with that of soybean meal without fermentation.While,the crude fiber of fermented soybean meal is 5.33%,reducing by 1.72%compared with that of soybean meal without fermentation.Thus,it is good for increasing nutritive value of soybean meal.And contents of crude fiber and water for fermented soybean meal are separately 3.04%and 5.57%,reducing by 0.47%and 1.09%compared with that of soybean meal without fermentation.Thus,it is good for extending the validity of soybean meal.However,there is not obvious change on total ash content.The changes of anti-nutritional factor for trypsin inhibitor,urease and phytic acid are declining,separately down to 10.98mg/g,0.01mg/g and 2.22mg/g.The experiment shows that fermented soybean meal has better nutritive value than that without fermentation.(3)Research for antioxidant properties of soybean peptides:The experiment of anti-oxidation in vitro shows that soybean peptides have strong antioxidant ability in vitro,especially good for removing off DPPH?O₂-·and·OH.And with the increasing of concentration of soybean peptides,the antioxidant ability in vitro shall be strengthened and the dose effect can be presented.The anti-oxidation in vitro shows that if feed experimental mice separately with 200mg,400mg and 600mg/kg of soybean peptides for 30 days,the soybean peptides can enhance the antioxidant ability of the mice and increase the activity of superoxide dismutase(SOD)and glutathione(GSH)in the livers of mice increase and reduce the content of malonaldehyde(MDA).It has obvious influence and presents some dose effect..