Isolation Of Phyllobacterium Sp. Nov. 921F With Yield Of A Noval Exo-polysaccharides And The Study Of Its Related Structure

Bacteria derived exo-polysaccharides are new kinds of products made by biology technology recently.Their different applications attribute to their different structures. According to currently reports,there are majorly three kinds of products,Xanthan,Gellan and Curdlan applied in industry,for example food,textile or petroleum and chemical indurstry.On the basis of finding and isolating the microb with properties of a new kind of exo-polysaccharide,high yield and stabilization,we tried many ways to isolate and culture it which we hope to hold high productivity and be applied widely in industry.A new kind of bacteria holding high exo-polysaccharides yield and stabilization was isolated through the compound screening methods of qualitative and quantitative analysis according to previous reports.The strain 921F was identified as Phyllobacterium sp.by micro-biochemical identification and 16S ribosomal RNA gene sequencing analysis.The medium components and culture conditions are optimized.Results show that the optimal culture medium is as follows:sucrose,3%;beef extract,0.45%;(NH₄)₂SO₄,0.04%; MgCl₂,0.03%.The optimal culture conditions are as follows:initial pH 7.0,temperature 30℃,medium volume 75 ml/250 ml,inoculum volume 8%(v/v),duration,72～96 h.The maximal exo-polysaccharide yield could reach 1.8%.In another hand,an experiment of 10 liter scaled fermentation was performed with the purpose of amplifying culture volume towards industry scale in the coming future.Exo-polysaccharides were precipitated with the use of ethanol and salt according to the optimal extracting process.Characters of exo-polysaccharides were investigated, including molecular weights,saccharides composition et al.IR,UV and AFM of exo-polysaccharides were performed to obtain more information about the molecular structure. The exo-polysaccharides we precipitated show highly viscous and translucent.So the experiment of apparent viscosity of exo-polysaccharides under different conditions were assayed,including the effects of substrate concentration,shear velocity,pH,temperature, durations,salts concentration et al.Method of enzyme hydrolysis was introduced to produce the final product from exo-polysaccharides. Tetrasaccharides,hexasaccharides and octasaccharides were separated and purified by passing through Bio-Gel P4 column several times.Molecular weights of the purified sections were determinate with MS.With the help of the information from upper charpter,ESI-CID-MS/MS and NMR of oligosaccharides were conducted to analysis its structure.So the structure of exo-polysccharides produced from Phyllobacterium sp.could be primarily illustrated.In the final area,we conducted some potential study about bioactivity of the related oligosaccharides,such as moisture absorption,moisture retention and fresh keeping of strawberry.The influence of oligosaccharide was also tested on the seed germination at different concentrations.Compared with the control,results indicate that the rate of seed germination was enhanced by increasing the activities of several enzymes beneficial for germination.