Study On The Production Of Higher Protease Activity Feeds With Soybean Meal Fermentation

Protease as a new feed additive, which can be broken down in vitro protein feed for the peptides and free amino acids under the optimum conditions, while in vivo synergy as an exogenous enzyme can help animal digestion and absorption of protein. In recent years, with the constantly deepened researches and application enlargement of protease preparation, protease as an exogenous enzyme on feed have drawn more and more attentions.Soybean meal is a feed with high-quality protein sources. Fermentation of soybean meal can be effectively dealt with the elimination of anti-nutritional factors, and improve feeding value of soybean meal. While the fermentation process of protein molecules were broken down into relatively small parts of proteins and small molecule peptide, in favor of animal absorption, reduce energy consumption. Therefore the different functional fermented soybean products are developed, and applied to animal husbandry will have great economic potential and broad prospect.In this study, in order to obtain high protease activity and peptide-rich fermented soybean products, soybean meal are solid-state fermented by using Aspergillus oryzae AS3.042 and Aspergillus niger AS3.350.First of all, the optimal medium and appropriate culture conditions of two Aspergillus Protease are studied. The results showed as follows:(1) The suitable culture medium and optimal conditions of neutral protease from Aspergillus oryzae were: soybean meal 8.8%, 35.2% wheat bran, water are 55%, KH2PO4 1.0%. Inoculum are 11%, at 30℃for 108h, under the optimal conditions, the average neutral protease activity is as high as 5863.5U/g.(2) The suitable culture medium and optimal conditions of acid protease from Aspergillus niger were: 22.5% soybean meal, wheat bran 15%, water 60%, NH4Cl 1.5%, KH2PO 41%. Inoculum 11%, at 30℃for 72h, under the optimal conditions, the average acd protease activity is as high as 2054.2U / g.At the same time, the characters of the protease from Aspergilluas oryzae and Aspergillus niger and impact of related factors were studied, the results are as follows:(1) The optimum temperature of Neutral protease is 45℃, and the optimum pH is 7.5. While the pH stability range is pH6.0-pH8.0, the enzyme heat resistance generally, 10min at 80℃constant temperature drying to maintain the vitality of 43%. Mg2+, Na+, Ca2+, Fe2+ all of the activity can be activated, while Cu2+, Fe3+, Mn2+, Zn2+ strongly inhibit the activity of such.(2) The optimum temperature of Acid protease is 45℃, the optimum pH of 3.5. pH stability range of pH2.0-pH4.0, good heat resistance of the enzyme, 10min at 80℃constant temperature drying can maintain the vitality of 64%. Metal ions Ca2+, Mg2+, Na+, Mn2+ and K+ on the enzyme activation significantly, while Cu2+, Fe2+, Zn2+, Fe3+ are generated on the enzyme inhibition.Finally, the process of high protease activity and more soybean peptide feed by solid state fermentation were studied. The dry koji inoculation is 13%, and the culture temperature is 30℃, fermeninting 24h, under the optimal conditions, the indicators of feed products showed as follows:(1) The neutral protease feed: the protease activity 4523.5U/g, hydrolysis degree 23.1%, the reducing sugar 6.5%.(2) The acid protease feed: the protease activity 4523.5U/g, hydrolysis degree 23.1%, the reducing sugar 7.2%.The products which are contain more protease and soybean peptides with low production costs, clean environment, high economic value, will be expected to promote in the animal husbandry industry.