Evaluation of nutritional quality of soybean meals fermented by Aspergillus oryzae.

This study evaluated the effect of fermentation of Aspergillus oryzae on the nutritional quality of soybean meals.Soybean meals were fermented by Aspergillus oryzae SICC 3.302 for 48 hours.After fermentation,their conventional nutritional contents,the composition of crude protein as well as the nutritional characteristics of protein were measured and corrected to the contents of nutrient on pre-fermentation base to compare with un-fermentation soybean meals.Results showed that the content of crude protein(CP) was un-changed,but the content of true protein(TP) reduced 19.19%(P0.05),and the level of non-protein nitrogen(NPN) increased nearly four-fold(P0.05),moreover,microbial protein was produced by 2.02% after fermentation.Fermentation increased the amount of small-size peptides(30ku)(P0.05) compared with un-fermentation soybean meals,while significantly decreasing large-size peptides(60ku)(P0.05) and medium-size peptides(30ku-60ku)(P0.05),and eliminating most of soybean antigens and anti-nutritional factors.Meanwhile,fermentation made the amount of NDF,ADF and NFE significantly decreased respectively by 16.77%(P0.05),12.57%(P0.05) and 22.25%(P0.05),while the content of crude fat increased 179.25%(P0.05).But fermentation made the amount of fermented substrate,protein and gross energy decreased 5.14%,3.06% and 3.86% respectively.These results indicated that fermentation could make protein in soybean meals to be degradated and become a more high-quality protein feed,with the cost of losing some carbohydrates and protein.