Preparation Of ACE Inhibitory Peptides From Liquid Fermentation Of Rice Bran By Compound Strains

The use of microbial fermentationfor preparation of rice bran ACE inhibitory peptides can reduce production costs, which is suitable for industrial scaleproduction.This paper focuses on four research areas:Firstly, screening strains that were used for the preparation of rice bran ACE inhibitory peptides by the compound liquid fermentation. Secondly, selection of raw materials that used for the preparation of ACE inhibitory peptides using compound liquid fermented rice bran. Thirdly, determination of fermentation conditions in compound liquid fermented rice bran for preparation of ACE inhibitory peptides. Finally, the separation, purification and stability analysis of rice bran ACE inhibitory peptides. All results were listed as follows:The tests were respectively using four single strains that were Bacillus subtilis, Bacillus licheniformis, Aspergillus niger, Aspergillus oryzae, and two mixed cultures that were Bacillus subtilis and Aspergillus niger, Bacillus subtilis and Aspergillus oryzae, in liquid ferment rice bran. ACE inhibitory activity was used as the main evaluation, also in combined with the nitrogen index of soluble amino nitrogen, the rate of obtaining rice bran protein peptides, screening strains used to preparation of rice bran ACE inhibitory peptides by the liquid fermentation. The results show that the mixed bacteria which were Bacillus subtilis combined with Aspergiilus niger to liquid ferment rice bran protein peptides, have the highest ACE inhibitory activity, and other indicators were also better than others. And the advantages of this strains were obvious, suited to using liquid fermented rice bran to preparation of ACE inhibitory peptides.The raw rice bran were popped and addition of starch, using pH value, amino nitrogen, protease activity, reducing sugar content, bran protein peptide conversion rate, ACE inhibitory activity of the fermentation products as index values to design experiments. And we decided to pop the raw rice bran as thepretreatment method. The results show that:ACE inhibitory activity and peptide conversion rate of peptides obtained puffed rice bran, and other indicators were significantly better than the starch rice bran and rice bran control group without any treatment.Puffed rice bran as raw material, using compound strains of Bacillus subtilis and Aspergillus niger was fermentation bacteria to liquid fermentation to preparation of ACE inhibitory peptides. ACE inhibitory activity as an indicator, the effects of different fermentation temperature, fermentation time, substrate concentration, initial pH value, the amount of inoculation, inoculated proportion, shaking speed to liquid fermentation ACE inhibitory peptide were studied. And the orthogonal experiments to determine that the optimal liquid fermentation prepared rice bran ACE inhibitory peptides process conditions:the substrate concentration of5.0%, fermentation temperature was34℃, fermentation time was22h, inoculation ratio of2:1. Following this optimal combination to verify test results showed that the inhibitory activity of ACE inhibitory peptide by prepared by liquid fermentation puffed rice bran reached72.0%.Using the polymer molecular weight were10KDa,6KDa hollow fiber ultrafiltration membrane, to separation and purification of rice bran ACE inhibitory peptides by ultrafiltration primary. Hollow fiber ultrafiltration membrane with MWCO6KDa could effectively improve the ACE inhibitory activity of rice bran peptides more than without ultrafiltration and other ultrafiltration components. The ultrafiltration membrane which molecular weight <6KDa ultrafiltrate fractions on the highest ACE inhibitory activity, ACE inhibition rate reached74.43%. Then <6kDa ultrafiltration component was further separated and purificated by using dextran gel Sephadex G-15column chromatography, and got five elution peak component, which was the fifth component has the highest ACE inhibition rate reached80.15%. And stability of the purified fraction was studied, thermal stability and pH stability of rice bran ACE inhibitory peptide were both well, ACE inhibitory activity were floating about70.0%. Rice bran ACE inhibitory peptides by simulated in vivo digestion trial, also had a higher ACE inhibitory activity.