Study On High-efficiency And Low-cost Fermentation And Transformation Mechanism Of Soybean Dregs Biological Feed

Soybean dregs and other industrial and agricultural by-products are abundant in Chain,but most of them are used as roughage to feed animals directly.And the utilization rate is low.The use of microbial solid state fermentation technology can convert bean dregs into high quality biological feed.This not only achieves the high value utilization of resources but also reduces the environmental pollution caused by the waste of bean dregs.The purpose of this study is to use bean dregs as the main raw material,bran as an auxiliary material and Bacillus,yeast and lactic acid bacteria as the main fermentation strains.By optimizing the fermentation conditions,various kinds of anti-nutritive substances?trypsin inhibitor,isothiocyanate,soybean antigen protein,etc.?in soybean dregs were removed,the contents of cellulose and hemicellulose were reduced,and the contents of soybean peptide and soybean isoflavone aglycone were increased.In addition,soybean peptide and soybean isoflavone aglycone were used as the main indicators.The optimal fermentation process for improving soybean peptide and soybean isoflavone aglycone in bean dregs was obtained by single factor experiment,orthogonal test and response surface experiment.Firstly,the content of anti-nutritional factors and each nutrient components of the raw material were examined before fermentation.Then,the removal rate of trypsin inhibitor and the removal effect of soybean antigen protein were used as the main detection indexes of anti-nutritional factors to screen the fermentation strains.Bacillus natto,Saccharomyces cerevisiae and Lactobacillus acidophilus were selected as the optimal fermentation strains.Then,the growth curve of the fermented strains used was determined,and the optimal culture time of each strain was determined.The optimal culture time for Bacillus natto,Saccharomyces cerevisiae and Lactobacillus acidophilus was 12 h,22 h and 26 h,respectively.The effects of single-fermentation and mixed-fermentation on the removal rate of trypsin inhibitor,the removal rate of isothiocyanate and the removal efficiency of soybean antigen protein were also investigated,and the method of mixed fermentation was established.Then,the effects of inoculation amount,water content of medium,fermentation temperature and fermentation time on the removal rate of trypsin inhibitor were investigated by single factor experiment.And the appropriate factor values were obtained.Then,the response surface experiment was carried out with the removal rate of trypsin inhibitoras as the indicator,and the optimal fermentation conditions were obtained.The optimum fermentation conditions were as follows:inoculation amount was 10.48%,water content of medium was 58.18%,fermentation temperature was34.42?,and fermentation time was 12.65 days.Under the optimal fermentation conditions,the removal rate of trypsin inhibitor reached 84.98%,the removal rate of isothiocyanate reached 73.33%,and the soybean antigen protein was completely degraded.Meanwhile,feed quality has also been greatly improved.Part of soy proteins were degraded by microorganisms into small molecules of soybean peptide.Soybean peptide increased by 2.43 times compared with before fermentation,and the content of cellulose and hemicellulose decreased by 12.96%and 31.99%,respectively.The finished feed after fermentation was golden in color,sour and fragrant,and soft in texture.The shelf life of the finished feed product was over six months,and the soybean isoflavone aglycone was also increased by 44.96%.It can be seen from the previous studies that microorganisms can degrade proteins into soybean peptide.After that,soybean peptide was used as the main detection index.The fermentation time,inoculation ratio,inoculation amount,addition amount of MgSO₄·7H₂O,different carbon sources and fermentation temperature were optimized by single factor experiment and orthogonal experiment.And the best fermentation conditions were obtained.The optimum fermentation conditions were as follows:inoculation amount was 16%,MgSO₄·7H₂O was added in an amount of 0.1%,temperature was 36?,inoculation ratio was 1:2,and carbon source was 1%bran.Under this condition,most of the soy proteins were degraded into small molecules of soy peptide by microorganisms.And the content of soybean peptide in the fermentation for 7 days reached 52.98%.It was 4.91 times the content of soybean peptide of the raw material.Soybean isoflavone aglycone has a much higher absorption rate than glycoside soybean isoflavones in the intestine,and its physiological activity is stronger than glycoside soybean isoflavones.The bean dregs contain a lot of glycoside soy isoflavones.Finally,the optimal fermentation strain?Lactobacillus plantarum PL70a?were screened by using the increase rate of soybean aglycones as a detection index.Then,the suitable conditions for various factors?different carbon sources,fermentation time,addition amount of sucrose,inoculation amount,addition amount of glucoamylase and addition amount of?NH₄?₂SO₄?were selected by single factor experiment.The response surface experiment was carried out with the three factors?inoculation amount,addition amount of glucoamylase and addition amount of?NH₄?₂SO₄?,and the optimal fermentation conditions were obtained.The optimal fermentation conditions were as follows:?NH₄?₂SO₄ was added in an amount of0.17%,the glucoamylase was added in an amount of 0.87%,and the inoculation amount was 17%.Under this condition,the improvement rate of aglycon-type soy isoflavones after fermentation for 3 days was 70.96%.This study obtained a set of high-efficiency and low-cost fermentation process of bean dregs biological feed,which provided a new direction for the rational utilization of bean dregs,laid a foundation for the industrialization of soybean dregs fermentation feed.And it also provided reference for other biological feed fermentation methods.