| Ginkgo biloba is a homologous plant of medicine and food.It has antioxidation and antibacterial effects and contains many active ingredients such as protein and flavonoids,which has a wide range of applications in medicine and food.The growth of Ginkgo biloba resources is affected by climate,geography,etc.,which affects its development and utilization.In this paper,Pseudomonas R6,an endophytic strain with high protein production,was screened from Ginkgo biloba and fermented to prepare bacterial protein.The function and structure of bacterial protein were compared with Ginkgo biloba seed protein.The aim was to produce ginkgo-like protein which could replace Ginkgo biloba seed protein by endophytic bacteria.The conclusions were as follows:The Ginkgo biloba seed protein was extracted by alkali extraction and acid precipitation method.The extraction conditions were as follows:material/liquid ratio[1:30?g/mL?],pH 10,extraction temperature?50??,time?2 h?,under the optimal condition,the highest yield reached 10.6%.The strains with high protein-producing ability were screened out from nine endophytic bacteria preserved in the laboratory.The endophyte R6 of Ginkgo biloba had the highest protein production.The endophyte R6 was selected as the target strain and identified as 16R rRNA.Finally,the strain R6 was identified as Pseudomonas,named Pseudomonas R6.Pseudomonas R6 was fermented to produce bacterial protein with a yield of 0.3 g/L.Both proteins were purified to give a single component.The SDS-PAGE analysis of the purified protein showed that the molecular weight of Ginkgo biloba seed protein was mainly17 KDa,and there was a small amount distribution between 25 KDa and 30 KDa.The molecular weight of the bacterial protein was mainly 48 KDa.Infrared spectrum analysis showed that proteins had high similarity,slightly offset,and both contained the characteristics of protein amide bands.The amino acid compositions of proteins were determined.It was found that the amino acid compositions of proteins were similar.They all contained 17 kinds of amino acids,but their contents were different.The Ginkgo biloba seed protein contained seven essential amino acids,including lysine 3.34%,phenylalanine 9.14%,methionine 0.14%,threonine 6.52%,isoleucine 2.03%,leucine 0.41%,valine 7.86%.It was a high-quality protein with abundant amino acid content.There were seven essential amino acids in the bacterial protein,including lysine 4.35%,phenylalanine 9.91%,methionine 0.16%,threonine4.9%,isoleucine 2.92%,leucine 0.3%,valine 9.9%.The microstructure of Ginkgo biloba seed protein and bacterial protein showed the same and different structures.The functional properties of Ginkgo biloba seed protein and bacterial protein were studied.The results showed that the bacterial protein was superior to Ginkgo biloba seed protein in solubility,oil-holding,foaming and emulsifying properties.The Ginkgo biloba seed protein was superior to bacteria protein in water-holding.In vitro antioxidant activities of Ginkgo biloba seed protein and bacteria protein were studied,and compared with the positive control VC.Within the concentration range,the reducing power of Ginkgo biloba seed protein was higher than bacteria protein.The IC50 of Ginkgo biloba seed protein and bacterial protein were 0.46mg/mL and 1.54mg/mL for the OH scavenging effect.The IC50 of Ginkgo biloba seed protein and bacteria protein were 3.16mg/mL and 4.18 mg/mL for O2-scavenging effect.The IC50 of Ginkgo biloba seed protein and bacteria protein were 1.43 mg/mL and 1.72 mg/mL for DPPH scavenging effect.The antioxidant capacity and concentration were positively correlated,and the antioxidant activity of Ginkgo biloba seed protein was higher than bacterial protein.This study provides a theoretical basis for the development and research of utilizing bacteria protein instead of Ginkgo biloba seed protein and solves the limition of ginkgo resources.It also provides a new way for the production and application of the active protein from Ginkgo biloba. |
PDF Full Text Request