Study On The Preparation Technology And Physic-chemical Properties Of Konjac ACE Inhibitory Peptides

Angiotensin I-Converting enzyme(ACE)inhibitory peptide is a kind of polypeptide that has inhibitory effect on ACE activity.In general,it consists of2~20 amino acid residues.Through a competitive combination of ACE inhibitory peptides with ACE,it can block the production of angiotensin?,as well as promote the generation of soothing peptides and enkephalin.Therefore,it can lower blood pressure.At present,the ACE inhibitory peptides prepared from mung beans,soy protein,casein,milk,wheat germ,oysters and other raw materials have been reported.However,few research reported the preparation of ACE inhibitory peptides from konjac.Some research results showed that the konjac flying powder was rich in konjac protein and can produce a variety of biological active peptide through the enzymatic technology,containing branched chain amino acid oligo-peptide(BCAAs),ACE inhibitory peptides,high F value oligo-peptide,mannatide,etc.The research and development of konjac flying powder,which is a kind of natural drug resource,is expected to create a new environment friendly way to prepare ACE inhibitory peptides.Konjac flying powder was selected as the raw material in this research.Konjac ACE inhibitory peptides was prepared through enzymatic hydrolysis.After ultrafiltration and macroporous adsorption resin separation and purification of preparation of konjac ACE inhibitory peptides.And it was carried on the quality detection and analysis of physical and chemical properties.Experiment results were as follows:1.Preparation of konjac ACE inhibitory peptides through enzymatic hydrolysis: Taken ACE inhibition rate as the examining index,the extraction process of konjac ACE inhibitory peptides were optimized by single factor and orthogonal experiments.The optimal enzyme pepsin was selected through screening experiment.The extraction conditions were confirmed as follows:substrate concentration of 2%,temperature of 37?,enzyme concentration of5000U/(g substrate),and pH2.5 for a hydrolysis of 210 min.Under these conditions,the ACE inhibition rate was 92.65%,the peptide yield was 12.60%.2.Ultrafiltration separation of konjac ACE inhibitory peptides: Taken ACE inhibition rate as the examining index to determine the appropriate interception molecular weight of ultrafiltration membrane was 1kDa.The best ultrafiltration conditions determined through single factor experiment and orthogonal experiment were as follows: peptide liquid concentration of 2%,pH4.0,temperature of 40?,15 min of ultrafiltration using 1kDa ultrafiltration membrane,and the ACE inhibitory rate was 92.75%.3.Macroporous adsorption resin separation of konjac ACE inhibitory peptides: Taken adsorption and desorption rate as the examining index,the best adsorption process conditions were determined by the screened DA201-C type of macroporous adsorption resin through adsorption and desorption experiments.The optimal adsorption process conditions were determined as follows: sample mass concentration was 8mg/mL,pH2.0,8mL of the sample amount,and the sample flow rate was 0.5mL/min.The desorption process condition was as follows: the eluent volume fraction of 80% ethanol,the elution velocity of1.0mL/min,and the elution time 2h.Under this condition,the ACE inhibition rate was 95.19%.4.Infrared spectrum of konjac ACE inhibitory peptides: The ACE inhibitory peptides after separated and purified was scaned by infrared spectrum,so did the ACE inhibitory peptides standard product.The analysis results showed that the two peaks were broadly in line with a peak shape and peak value.The possible absorption peak was O-H,N-H,amide bond,C-O and aromatics C-H bending vibration,etc.Comprehensive analysis showed that the konjac ACE inhibitory peptides and the standard sample's infrared spectral characteristics were basically identical.5.Using the ultraviolet wavelength scanning to test the konjac ACE inhibitory peptides,it was found that its maximum absorption peak was at220 nm,standard sample's scan results consistent with the konjac ACE inhibitory peptides.The high performance liquid chromatography(HPLC)analysis results showed that konjac ACE inhibitory peptides were similar to standard peak shape characteristics.By ultraviolet spectrophotometry,the concentration of purified konjac ACE inhibitory peptides was 81.37?g/mL.By gel permeation chromatography,the peak molecular weight(MP)and the molecular weightrange of konjac ACE inhibitory peptides was 655 Da and 500~700Da.6.The physical and chemical properties of konjac ACE inhibitory peptides:Results showed that konjac ACE inhibitory peptides were gray solid powder with a stench after ectraction and separation.Its solubility in water at room temperature can reach 95% when the pH was 2.0.Konjac ACE inhibitory peptides presented good stability at 30~50?.However,its ACE inhibitory rates were close to zero when placed in 90? water bath for 5h.When placed at room temperature with pH of 2.0~4.0 for 2h,its ACE inhibitory rates changed little.While the pH value increased gradually,its ACE inhibitory activities decreased gradually.The ACE inhibitory rates could remain at 90% when placed the peptides at room temperature with 0.2~0.6mol/L NaCl concentration for 2h.The konjac ACE inhibitory peptides were stable in the digestive enzymes at 37?,and the ACE inhibition rate maintained at 85%.