Identification Of Endophytic Bacteria From Ginkgo Biloba L. And Optimization Of Fermentation Conditions For Extracellular Polysaccharides Of Endo Gin Ya6

Polysaccharides from Ginkgo biloba L.(GBLP) is a kind of functional polysaccharides with immunomodulation, anti-tumor and lowering blood pressure. But the extraction of plant polysaccharides usually depends on season, growing-area and other natural conditions, and which may lead to the depletion of natural resources. The same or similar biological active substances like its symbiotic plant can be obtained from the fermentation of endophytic bacteria. So endophytic bacteria were screened from healthy Ginkgo biloba L. tissue, then polysaccharides were prepared. The research provides a new way for further development and application of Ginkgo biloba L. polysaccharides.A strain with high yield of extracellular polysaccharides from health Ginkgo plant was identificated, the fermentation media and culture conditions of extracellular polysaccharides of this strain were optimized, then EPS-soybean protein conjugates by Maillard reaction was prepared, and the antioxidant activities were determined. The main research results are as follows:1. Endo Gin Ya6 was identified as Bacillus by physiological and biochemical experiments and 16 S rDNA sequence analysis, and the homology of Endo Gin Ya6 with Bacillus and Lysinibacillus sphaericus are 99%, Phylogenetic analysis showed that Endo Gin Ya6 has an independent branch.2. The optimal media of the Endo Gin Ya6 are tested by single factor and orthogonal experiments(g/L):sucrose 120, yeast extract 8.0, NaCl 5.0, K2HPO4 1.0, KCl 1.0, pH 7.5; The optimal fermentation conditions are:250mL flask containing 70 m L medium, 28℃, shaker revolutions 200 r/min, inoculum volume 2%, 30 h. The maximum yield of the EPS is 10.27g/L.3. Protein was removed with Sevag method, then EPS from Endo Gin Ya6 was dialysed. EPS was combined with soy protein by Maillard reaction.4. Antioxidative activitis of the EPS and the EPS-soybean protein conjugates were analysized. The results showed that scavenging of EPS and EPS-soybean protein conjugates to O2-· were 29.23% and 31.92%, respectively. Meanwhile, they also showed the abilities of scavenge DPPH·, ·OH, Fe2+ and reducing power, and the ability of EPS-soybean protein conjugates was better than that of EPS.