Study On Degradation,Structure And Antioxidant Activity Of Passiflora Edulis Sims Peel Polysaccharide

In this paper,the Passiflora edulis Sims peel was used as the raw material,todegrade the polysaccharide by Vc-H₂O₂ method and enzymatic method.The response surface method was used to optimize the process conditions of Vc-H₂O₂ degradation of Passiflora edulis Sims peel polysaccharides,the degraded polysaccharide DWPEP was obtained,the structure of polysaccharides before and after degradation was characterized,and its antioxidant activity in vitro was compared.The crude enzyme solution of Aspergillus japonicas PJ01 in solid-state fermentation was used to degrade the Passiflora edulis Sims peel polysaccharides,and studied its structure and in vitro antioxidant activity.The specific research results were as follows:（1）Based on the results of single-factor tests and response surface analysis,the optimal process for analyzing Vc-H₂O₂ method to degrade the polysaccharide of Passiflora edulis Sims peel was:the Vc-H₂O₂ concentration 9.32 mM,the degradation temperature 52.06°C,the degradation time 1.42 h,at this time the DPPH·radical scavenging ability was 45.59?0.45%.The experimentally fitted second-order model had a correlation coefficient of R²=0.9944,an F-value of139.25,and a P-value of<0.0001,these figures illustrated the reliability of the model,and also determine that time was the most significant term,the values of the variables were also optimized,including 45.59%of the predicted degradation and 0.4492 of the expected value.The physical and chemical properties of WPEP and DWPEP were characterized,and the results showed that the sugar content of the samples increased slightly after degradation,the sulfate content and uronic acid content decreased,and the molecular weight decreased from 118 kDa to 38 kDa.The monosaccharide composition has changed.The monosaccharide composition of WPEP were rhamnose,glucuronic acid,galacturonic acid,and arabinose,and their contents were 2.27%,7.97%,87.44%and 2.30%,respectively;the monosaccharide composition of DWPEP were mannose,rhamnose,galacturonic acid,glucose,galactose,xylan and arabinose,and their contents were 3.51%,4.07%,77.68%,5.15%,4.44%,2.30%and 2.85%,respectively.The results of infrared spectrum and XRD experimental results showed that the characteristic absorption peaks and crystal structures of Passiflora edulis Sims peel polysaccharides were very similar before and after degradation.The DPPH free radical scavenging ability,reducing energy and hydroxyl radical scavenging ability of passion fruit peel polysaccharide before and after degradation were studied.When the concentration was 3.2 mg/mL,the DPPH free radical scavenging rates of WPEP and DWPEP were 93.03%and 81.70%,the reduction ability were 0.689,0.52,and the hydroxyl radical scavenging rates were 53.99%and 26.59%.The degradation ability and reduction ability of the Passiflora edulis Sims peel polysaccharide were lower than those before degradation.（2）When WPEP was mixed with the crude enzyme solution at a ratio of 1:200（w/v）,it could be completely dissolved in water bath at 45°C,and WPEP could be completely hydrolyzed in an air shaker at 45°C for 6 h to obtain EWPEP.The sugar content and uronic acid content of EWPEP were lower than slightly WPEP,the protein content of WPEP was higher,and the sulfate content of EWPEP was much higher than WPEP,15.03?0.13%.Monosaccharide composition results showed that the monosaccharide composition of WPEP and EWPE were different.WPEP consists of rhamnose,glucuronic acid,galacturonic acid,and arabinose;EWPEP consists of rhamnose,galacturonic acid,glucose,and galactose,and galacturonic acid was the main component,the contents were 87.44%and 56.80%,respectively.The molecular weight distribution of WPEP showed a uniform symmetrical peak with an average molecular weight of 118 kDa,and that of EWPEP was three peaks with an average molecular weight of 101 kDa,2 kDa,and 1 kDa,respectively.Infrared results showed that both WPEP and EWPEP had characteristic peaks of polysaccharides,which were polypyranose,and degradation did not change the major functional groups.The UV absorption spectrum showed that EWPEP had a small absorption peak at 280 nm,indicating that EWPEP contained a small amount of protein.Scanning electron micrographs showed that enzymatic degradation destroyed the surface structure of WPEP.In vitro antioxidant activity experiments showed that the DPPH free radical scavenging ability,reducing ability,hydroxyl radical scavenging ability,and superoxide anion scavenging ability of WPEP and EWPEP were proportional to the concentration.When the concentration was 3.2 mg/mL,the DPPH free radical scavenging ability of WPEP and EWPEP were 94.94%and 95.78%,reducing ability were 0.72 and 1.08,hydroxyl radical scavenging ability were 29.54%and 65.47%,and superoxide anion scavenging ability is 20.52%and 34.43%,EWPEP has higher antioxidant activity than WPEP.