Study And Comparison Of Two Kinds Of Microoganism Fermentaton Degrading Antarctic Krill Protein

In this study, on the basis of enzyme production by microbial fermentation, the microoganism fermentaion process of degradation of the Antarctic Krill meal protein was studied. First, the fermentation conditions of protease production by Bacillus licheniformis were optimized, and the protease would be used for subsequent experiments to the Antarctic Krill meal protein degradation; the main influence factors of solid-state fermentation Antarctic Krill meal by Aspergillus oryzae were discussesed, the fermentation parameters were optimized, layed a theoretical basis for microbial method utilization of Antarctic Krill meal. The main results were showed as follows:(1) Optimazation of the Fermentation Conditions of Bacillus licheniformis Producing ProteaseOn the basis of the single factor tests screening liquid fermentation conditions of Bacillus licheniformis to produce protease, taken the protease activity as index, the fermentation conditons of protease production by Bacillus licheniformis were optimized through the L9(34) orthogonal experimental design. The results showed that the effects of fermentation temperature, fermentation pH, fermented bottle filling ratio and fermentation time on protease production were very significantly. The optimized fermentation conditions were that:fermentation temperature 37℃, fermentation pH 8, fermented bottle filling ratio 40%, and fermentation time 4 d, respectively. Based on this condition, the protease activity in the Bacillus licheniformis fermented liquid was 566.5±0.38 U/mL(2) Optimization of the Conditions of Bacillus licheniformis Protease Degrading Antarctic Krill ProteinThe protease produced in the previous chapter was used in Antarctic Krill mealprotein enzymolysis process, the effects of enzymolysis temperatrue enzymolysis time, enzymolysis pH and the ratio of Antarctic Krill meal and fermented liquid on Antarctic Krill meal protein enzymatic hydrolysis were discussed by the single factor tests. The quadratic orthogonal rotary combination was used to establish the mathematical regression equation about the soluble protein content Y of Antarctic Krill meal protein enzymolysis liquid and the enzymolysis pH X1, the enzymolysis temperature X2, the enzymolysis time X3:Y=179.38+3.31X1-6.60X2+12.72X3-5.67X12-8.36X22-6.68X32+4.80X1X2-2.35X1X3Through Response Surface Methodology (RSM), the key enzymolysis technology parameters combination of Antarctic Krill meal protein was optimized as follows:the enzymolysis temperature of 60℃, the enzymolysis time of 13 h, the enzymolysis pH of 10. Under these conditions, the soluble protein content of Antarctic Krill meal protein hydrolyzate was 185.8±0.35 mg/mL, and there were no significant differences between the theoretical value and the actual measured value (p>0.05), and the amino nitrogen content was 21.7±0.18 mg/mL, was 19.7 times of amino nitrogen content of the raw material (1.1±0.24 mg/mL). The result presented the anmino nitrogen content could have been significantly (p<0.01) improved by used the protease produced by Bacillus licheniformis fermentation to hydrolysis Antarctic Krill protein.(3) Research on the Solid-state Fermentation Conditions of Antarctic Krill Protein by Aspergillus oryzaeThe effects of fermentation temperatrue, fermentation time, the ratio of Antarctic Krill meal and bran, inoculum size and water addition ratio on the Antarctic Krill meal solid-state fermentation by Aspergillus oryzae was discussed by the single factor tests. Basing on the quadratic orthogonal rotary combination experiment, the mathematical regression equation about the soluble protein content Y of the fermentation product and the fermentation temperature X1, the inoculum size X2, the water addition ratio X3 had been established:Y=103.86+5.66X1+3.33X2+4.08X3-6.13X12-3.73X22-2.40X32-2.43X1X2The optimized solid-state fermentation technology parameters of Antarctic Krill meal had achieved through the response surface method:the fermentation temperature 32℃, the inoculum size 5%, the water addition ratio 110%. Under these conditions, the soluble protein content of solid-state fermentatin product was 105.9±0.37 mg/mL, and there were no significant differences between the theoretical value and the actual measured value (p>0.05), and the amino nitrogen content was 8.6±0.24 mg/mL, increased 7.5 times than anmino nitrogen content of the raw material (1.1±0.24 mg/mL)Comparing the above two kinds of fermentation methods on the Antarctic Krill meal protein degradation, it was better that using Bacillus licheniformis fermentation to produce protease firstly and then degrading Antarctic Krill protein, due to its enzymatic process provided appropriate action conditions for protease, which was an ideal method to degrade Antarctic Krill protein.