Research On Screening And Fermentation Optimization Of Lactobacillus Acidophilus, Analysis Of Exopolysaccharide

Polysaccharide is a carbohydrate desiccated by a lot of monosaccharide molecules, accorded with derivative of the macromolecular compound concept.Polysaccharides are complicated and huge carbohydrate materials of a kind of molecule organization. Polysaccharides of Bacterium mainly exist in three kinds of forms:polysaccharides outside cell wall,in the surface of cell wall and in afterbirth.Polysaccharides mainly exist in the form of glucogen,playing a role in storing energy in the afterbirth.Afterbirth wall; polysaccharides keep cell structural and shape,principal ingredients of which are many carbohydrate material and protein used for taking shape in conjunction with fat such as peptidoglycan,lipopolysaccharide and lipoteichoic acids.Many lipoteichoic acids mean candy(glycocalyx) outside the afterbirth of broad sense.Its main function is to get up and protect engulfing,storage nourishment,piling up some supersession results and surfaces to suck that the bacterium avoids lacking water.Polysaccharides mean mucus layer,that is one diffused material to get culture medium outside the afterbirth of narrow sense,it is outside people's usually said microbial exo-polysaccharides too.The lactic acid bacteriums are that a kind of inherent in the human intestines which can ferment and utilize carbohydrate and produce the bacterium of a large number of lactic acids,it is admitted as the safe fermented bacterium to human body by U.S.A.FDA. Among them it is advantage bactereas group in the human intestines to have a liking for the bacillus of yahourth.It is a fermented bacterium of industry with a long history to have a liking for the bacillus of yahourth.It has a more obvious advantage in certain application.Not merely it has important influence with the flavor that the quality to the dairy products is constructed to have a liking for outside the bacillus afterbirth of yahourth.LABs may become food grades polysaccharides and apply various foods to increase viscosity extensively,stability,emulsification and keeping moisten.The research on bacterium's polysaccharides has already been relatively deepened at present.But research on the exo-polysaccharides of lactic acid are started just,structure and biological activity function of polysaccharides of some lactic acid bacterium are not confirmed and verified yet.Fermented conditions and producing environmental factor of Lactic acid polysaccharides are also remain to clarify.the suspected bacterial strain isolateed from the commercial yoghurt was selected by shaping characteristic of examining through the microscope,and confirmed to lactobacillus through gelatin liquefaction,exposed to enzyme react,nitrate reduce,indole and sulfide hydrogen react.At last,lactobacillus acidophilus is confirmed by carbohydrate fermented experiment and 16sDNA PCR examination.Lactobacillus acidophilus mutation whose yield of exo- polysaccharides reaches 6.46g/L have been screened by ethyl sulfateThe output of exo-polysaccharides of Lactobacillus acidophilus was Measured in different fermented conditions.16 different fermented factor were analyzed with Placket-Burman method and getting most influential 3 factors to the output of exo-polysaccharides of Lactobacillus acidophilus;Through optimizing by respond surface method to 3 fermented terms,the output of exo-polysaccharides of Lactobacillus acidophilus reaches 3.85g/LThe fermented broth is precipitated at 4℃by alcohol overnight,orthogonal design is analyzed with alcohol concentration,the ratio of material to water on extraction rate,time of extraction respectively for influencing factor.The results demonstrated that under alcohol concentration 80%,by 1:1.8 material to water,extract 12h,the output reacheed 1.91g/L.The sediment will be dissolved with distilled water and dialysed 48h before lyophilizing.The solution was purified by Cellulose 52 and Sephadex G-200.Most big molecular weight was assembled for the structure analyse.The structure and composition of polysaccharides of lactobacillus acidophilus were determined by Infrared spectrum and the GC analysis determine the molecular.