| Cottonseed meal is a source of plant protein feed, the crude protein content between 36%- 45%, which contains a variety of vitamins and minerals and other nutrients, aslo contains Free gossypol, Cyclopropenoid fatty acid, Phytic acid, Tannin anti nutritional factor, thus limiting its application in animal husbandry and aquaculture industry. One of the most important step of feeding cottonseed meal is to reduce the content of free gossypol. Therefore, to be detoxificated the cottonseed meal becoming an important research on its development of utilization value. Generally, the methods of removing free gossypol have chemical method, physical method, solvent extraction and microbial fermentation. The study of microbial degradation the free gossypol date from abroad. The method was also gradually established that was solid fermentated cottonseed meal by microbial to be degradated free gossypol in our country. Solid fermentation cottonseed meal by microbial not only reduced the content of free gossypol, but also improved the nutritional value of cottonseed meal after fermentation, such as protein content,the content amino acid.Test results are as follows:(1) Experiment 1:It was separated two strains of bacteria M1, M2 and a strain of filamentous fungi M3 by using the Sugar free gossypol Czapek medium from the cotton seed shell, and only the M2 could degrade free gossypol efficiently by solid-state fermentation, and the M2 was identified as Klebsiella oxytoca by 16 S rDNA molecular biology. It get two strains that were Candida utilis yeast and M2 could degrade free gossypol highly efficient by solid state fermentation of single strain. It was obtained the best combination of fermentation from two two compound fermentation that was Candida utilis yeast and M2.(2) Experiment 2: It is mainly discusses the effect of lactic acid bacteria and substrate materials on solid fermentation. The results showed that lactic acid bacteria had no significant influence on degradation of free gossypol by composite solid fermentation; It was getting the best combination substrates by solid-state fermentation of different substrates that was Cottonseed meal: Bran: Corn flour =6:2:2. The degradation rate of free gossypol reached 58.28% in this condition.(3) Experiment 3:Through the use of two factor with repeated observation of the value of experiment and the uniform experimental design optimizing the fermentation process parameters for DPS v7.05 statistical software. Drawn the optimum conclusion of solid-state fermentation cottonseed meal was that the inoculation was 4 mL/100 g, Candida utilis and M2 inoculation ratio was 7:3, fermentation temperature 32.5, fermentation time 54 h, initial substrate moisture content 75%. The degradation rate of free gossypol reached 53.021% in this condition(4) Experiment 4: Through the Plackett-Burman test of DOE for Mintab 16 and the test of uniform design in DPS v7.05 software to be ptimizing the additive amount of salts in solid state fermentation. Finally obtains the best combination of each factor is X1(urea) 1.44%, X2(three citric acid ammonium(X3) 0.2%, 0.2%, X4(choline chloride) two potassium hydrogen phosphate) 0.34%, X5(Magnesium Sulfate) 1%, X6(copper sulfate) 1%, X7(manganese sulfate) 1%, X8(zinc sulfate) 0.1%.(5) Experiment 5: Through verification test comparised the changes of some materials of the fermentation substrate before and after fermentated, the free gossypol degradation rate reached 65.254%; crude protein content increased by 2.037%; protein molecular weight changed little, but no molecular weight above 66.2 kDa; the living number of Candida utilis was 7.2×109, M2 was 3.5×108, the content of amino acid also have changed. |
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