The Study Of Soybean Meal Fermentation With Aspergillus Niger

Fermented soybean meal is a new type vegetal protein which can be used as feed protein source. It is a great substitute for animal protein because of its cost and high quality of nutrition. However the protein content of fermented soybean meal used the existing fermentation technics is around 50% and it is hard to improve.Inorder to get high protein content of fermented soybean meal, the subject of our reaserch is trying to change the existing fermentation method, which used bacillus as a fermentation strain, and use fungi to ferment soybean meal. The fungi have their own advantages: strong growth, enzyme production ability, and abundant of enzyme. Use the protein content of soybean meal as an indicator, Aspergillus niger was selected from five fungi which can highly increase the prtein content of soybean meal. Compared with fermented with Aspergillus niger alone or mixed with other strains, we finally choose fermented with Aspergillus niger alone. Orthogonal experiment was used to optimize the factors that affect soybean meal fermentation: culture time, the amount of inoculums, the ratio of raw materials and water, the original temperature and fermentation volume. By analysis the data, the best fermentation conditions are: culture time 3 days, the amount of inoculums 0.5%, the ratio of materials and water 1:1, the original temperature 35℃, fermentation volume 20g.The nutrition value of soybean meal has been greatly improved after fermentation. The content of crude protein and total amino acid of soybean meal enhanced from 43.57% to 60.14% (increased by 38.03%) and from 39.68% to 53.87% (increased by 35.76%) respectively. The content of main anti-nutritional factors in soybean meal decreased to a very low degree after fermentation by Aspergillus niger. The content of trypsin inhibitor decreased from 1820 TIU/mg to 480 TIU/mg and the content of physic acid decreased from 9.464 mg/g to 0.434 mg/g. The lipoxygenase and urease activity were completely decomposed from -0.038 and 0.136 respectively. The hemagglutinin (10240 units) was reduced to 80 units.