Preparation Of Small Peptides From Chicken Blood Hemoglobin By Aspergillus Niger

This study investigated small molecular peptide production process by hydrolyzing chicken blood hemoglobin(Hb) with Aspergillus niger, which could excrete acid protease. Main contents includes extraction process optimization of Hb by UHP with the response surface optimization technology, process optimization for production of bioactive peptide by decomposing Hb with A. niger, effects of non-ionic surfactants on preparation of Hb bioactive peptides by A. niger and Hb peptide production by hydrolyzing with enzymes. The main results are as follows:Extraction process of Hb by UHP was optimized in two steps. Firstly, effects of material/solvent ratio, treatment time, pressure, p H and temperature on Hb yield were investigated with single factor experiment. Secondly, extraction condition for Hb by UHP was optimized with response surface optimization experiment adopting above-mentioned parameters for Hb rate as the response.. In the meanwhile, the role of ultra-high pressure in improving Hb functional properties, such as emulsifying properties and foaming capacity, were also revealed.The optimal extraction conditions were material/solvent ratio 1:2.5, 135 MPa for 5.4min. Under the optimal condition,Hb yield achieved 6.70g/100 m L with better emulsibility, foaming capacity and foam stability.Orthogonal design was employed to optimize medium component for A. niger.Based on the optimized medium, effects of inoculum size, loading volume,temperature and fermentation time on Hb degradation ratio were also studied. Hb degradation ratio increased 18% with the optimized fermentation process.Effects of edible non-ionic surfactants on Hb peptide production by A. niger were evaluated.Results showed that, when adding 6 g/L dodecyl polyglucoside in 48 h, 0.64 mg·N/m L Hb was achieved within 64 h fermentation. Molecular weight distribution test by gel chromatography showed that peptides with MW 450~2000 of non-ionic surfactant group was significantly more than that of control.To compare Hb hydrolysis activity of enzyme from A. niger with commercial protease and determination of molecular weight by enzymatic hydrolysate, proteases in the broth were separated and purified. Results showed that, compared with acid protease, neutral protease presented higher Hb hydrolysis ability but with lessr target product(Hb) yield, implying their different enzymatic characteristics. It was showed that the target product Hb polypeptide could be obtained by the degradation of Hb with Aspergillus niger.