Research On Preparation And Activity Of Plant-based Immune Function Peptide Through Microbial Fermentation Method

In recently years,the research confirmed that peptides were the most easily absorbed and utilized edible protein products.Plant peptide is a kind of edible protein products with rich resources,and the preparation of peptide from corn accounts for a large proportion in plant peptide production.Corn peptide(CP)is the hydrolytic product of corn protein.It can improve the water-insoluble of corn protein,and has higher physical and chemical properties and biological activity.At present,the reported active functions of corn peptide mainly include sobering up,liver protection,anti-fatigue,anti-oxidation and so on,which is one of the products sought after by health products industry.However,according to the composition of corn peptide,corn peptide still has important immune function,which has not been researched in depth.This paper aims to modify the structure of the corn peptide chain by microbial transformation,to fully express its immune function,to expand the application field of corn peptide.In this paper,a biotransformation pathway which can enhance the immune function of corn peptide was obtained through the following experiments.(1)Through gene comparison,the protease decomposition function of Bacillus subtilis Bls-45 was confirmed.Based on the rich characteristics of the enzyme system,Bls-45 was identified as corn peptide transformation strain,and its transformation medium and transformation process conditions were further explored.(2)The donor groups of Corn Peptides modified by microorganism were selected.The ratio of corn peptide to donor group and the pH value of the reaction were studied through the conversion effects of different sugars,acids and metal ions with the substrate.The best modified donor was glucose,and corn peptide glucose derivative(CP-G)was obtained;Through single factor and response surface methodology,the optimal conversion system was determined as follows:substrate concentration of 6%,substrate to donor ratio of 8:1,and the conversion effect was the best at pH 8.(3)According to the fermentation process,the single factor experiments of inoculation amount,fermentation time,fermentation temperature and other factors were carried out,and the response surface optimization test of four factors and three levels was carried out.The optimal conditions were obtained as follows:inoculation 10%amount of Bls-45,pH 6,fermentation temperature 37?,fermentation time 46h.(4)The crude CP-G concentrate was separated by 0.1-0.5kDa dialysis,6kDa ultrafiltration and SephadexG-25 column chromatography.The molecular weight of crude CP-G was 2863Da,680Da and 181Da,respectively.By the determination of DPPH scavenging capacity,680da component had the best effect.(5)By comparing CP-G with CP in ultraviolet absorption spectrum,infrared absorption spectrum,amino acid composition and graft degree determination,it is proved that CP-G is a glycosylated product formed by Maillard reaction between glucose and corn peptide through covalent bond;there is o-glycopeptide bond in CP-G molecule,and the glycosidic bond type is a type.(6)By comparing the physicochemical properties of CP-G and CP,it is proved that CP-G has better solubility,emulsification,foaming power and in vitro digestibility.(7)Compared with CP-G and CP in vitro and in vivo,the results showed that CP and cp-g could reduce the content of MDA in serum and liver,and increase the activity of SOD and GSH-Px in serum and liver.However,glycosylated CP-G could significantly improve the antioxidant capacity of CP in vitro and in vivo;The antioxidant effect of CP-G combined with lentinan in vivo showed that CP-G had synergistic effect with lentinan,and had higher antioxidant function than CP-G itself.(8)CP and CP-G immune function test showed that CP-G's nonspecific immunity test,cellular immunity test and humoral immunity test were significantly improved compared with CP;the experiment proved that CP-G could synergize with lentinan,and it had higher immune function than CP-G itself.The antioxidant and immune function tests in vivo showed that CP-G had good synergism and compatibility potential with other preparations.