Study On Solid State Fermentation Of Feather Powder With Mixed Keratin-Degrading Strains NJQ2 And NJQ3

With the rapid development of animal husbandry in our country, the demand of protein feed increases sharply, and mainly rely on imports to make up this deficiency will bring too much cost. On the other hand, the crude protein contents in poultry feathers is up to 80% or more,millions of tons of feathers are not reasonably used every year, which is polluting the environment, and also wasting protein resources. As the protein in poultry feathers is mainly composed of keratin, it cannot be digested by animal until its chemical structure is destroyed during processing. The test used feather powder, which was processed by high-temperature and high pressure hydrolysis, supplemented with wheat bran as the culture medium, and also with keratin-degrading strains NJQ2 and NJQ3 screened in laboratory as the microbial inoculant. This study also focused on solid state fermentation with the mixed strains, the digestibility of the fermented product by a pepsin-pancreatin in vitro method to improve the feather powder nutrition value. The results are shown below:The optimum medium of solid state fermentation with mixed keratin-degrading strains NJQ2 and NJQ3:feather powder 25 g, wheat bran 25 g, NaC1 0.3 g·L-1, K2HPO40.09 g-L"1, KH2PO40.36 g·L-1, MgSO40.15 g.L-1; the optimum fermentation condition:the initial pH value 7.5,5 mL inoculation size, fermentation temperature 37 ℃,the inoculation proportion of NJQ2:NJQ3 is 3:2, medium thickness 1.5 cm. After 6 days fermentation process with the optimization fermentation medium, soluble protein content was 6.62 mg/mL and weightlessness rate of solid state fermentation products was 54.80%.We used vitro digestion fermented products in different solid state fermentation conditions by a pepsin-pancreatin in vitro method, and combined this method with the specific digestibility and weightlessness rate in vitro to obtain the degradation rate of solid state fermentation. The results indicated that the optimum fermentation medium, after 6 days tray fermentation, in vitro digestibility and degradation rate, reached 52.01% and 82.30% respectively.Study on solid state fermentation process under the optimal conditions:The results showed that within 24 hours solid state fermentation, the color of culture medium deepened, the pH value rapidly increased from about 6.0 to 8.0 or above, and remained at a higher level. The content of soluble protein and ammonia nitrogen in fermentation supernatant increased with fermentation and reached to the highest in the 6 day respectively, then showed a slight downward trend.In order to evaluate the safety concern of NJQ2 and NJQ3 strains and its fermented products, we used bacteria liquid and fermentation supernatant as raw material to do the white mice acute toxicity test. The white mice were given raw material three times in one day by gavage, every 8 hours were administrated once and 0.6ml dose each time. Continuous observing 14 days, mouse group did not die,they were alive and well.The mice’s weight and feed intake of bacteria liquid group had no obvious difference comparing to the mice in control group, while the mice weight of fermentation liquid group had significant differences comparing to the mice in control group, indicating its feed utilization rate increased. Experiments proved that the NJQ2 and NJQ3 strains were murine safe.