Rearch On Improving The Cottonseed Meal To Produce Quality Oligopetides Feedstuff By Fementation

The cottonseed meal is rich in protein but its husbandry application is restricted because of the low digestive rate. To solve the protein shortage problem, it is of significance to improve the cottonseed meal protein quality. In this study, solid-state fermentation was used to degrade macromolecular protein to small peptides, to reduce the peptide length and balance the amino acid nutrition.Four strains, which can efficiently improve the cottonseed meal protein, were isolated from the samples. They could be classified as Bacillus cereus (1 strain, named as B.cereus H9), Bacillus subtilis (2 strains, named as B.subtilis H1 and B.subtilis H7) and Aspergillus niger (1 strain, named as A.niger P1) preliminarily. Both individual and combined fermentations were carried out. The results showed that under the optimal strains combined (B.subtilis H1 and A.niger P1) fermentation, the content of small peptides increased to 15.36%, the length of average peptide chain fell down to 5.16, and the digestibility of protein increased from 44.56% to 78.61%. The results showed that under the combined fermentation by strains (B.subtilis H1 and A.niger P1), the cottonseed meal protein can be improved effectively.With the increase rate of small peptides and the length of average peptide chain for index, the study on the condition of combined fermentation was carried out by single factor and orthogonal test. The results showed that the optimal fementation condition was as follows: the fermentation matrix 40 g, bran 15%, (NH4)2SO4 0.2%, KH2PO4 0.5%, water content 50%, nature pH, temperature 30℃, inoculation quantity 15%, fermentation time 60 h and the optimum inoculation 2:1 (P1:H1). Under the optimum condition determined the increase rate of small peptides increased by 101.7%, the length of average peptide chain decreased by 0.93 and the digestibility of protein increased by 9.98%.The two strains have "collaboration". A.niger P1 can produce rich acid protease while B.subtilis H1 can produce rich neutral and alkali protease. Under the combined fermentation, the enzymic activity significantly increased. The peptides composed of more than 10 amino acids in the water-soluble peptides were almost degraded to peptides composed of 1-3 amino acids, which was better than single fermentation.After the combined fermentation the molecular weight of protein dropped from 66 KD to below 14 KD. The utilization of protein was improved. The composition of the amino acid trended to be balanced. The content of rough fiber decreased by 33.60%, meanwhile the content of reducing sugar increased by 430% of the content before fementation. The energy efficiency was improved. The total content of amino acid increased by 15%, riching the protein nutrition. The content of the essential fatty acid-linoleic acid has increased by 18.94%. The organic acid flavor substances such as the lactic acid were produced, which can improve the palatability. The cottonseed meal was improved effectively.