| Bacterial cellulose(BC)is a kind of pure cellulose consisting of glucose molecules linked by β-1,4-glycosidic bond produced by bacteria.It is used by novelty and safety biological material with its excellent performance because of good bioafinity,biocompatibility,biocompatibility and biodegradability,therefore it have broad application prospect in the food industry,papermaking,acoustic equipment,oil extraction,artificial skin and medical materials.There are large numbers of byproducts in the non-direct pathway limited the increasing of BC yield and it’s a key reason of low production.Based on current issues this article used method of adding acid exogenously utilize Gas Chromatography and Mass Spectrometry researching the metabolic profiling of Gluconacetobacter hansenii product BC under acidic stress.Investigate influence of acid to strain physiological metabolism and production of BC.The main result is:Single factor experiment GC-MS methods optimizing critical processes,and methodological study from the precision,repeatability and stability,obtaining the optical analysis Parameters:80℃ keep 2min,2℃/min to 165℃ keep 2min,1℃/min to 180℃ keep 2min,20℃/min to 300℃;split ratio 10:1,electron impact ionization 70eV,full scan mode 50-600,ion trap temperature 220℃,Transfer line temperature 280℃,Electron multiplier 100eV,ionization off time 3min.The experiments also indicated good stability of the instrument and within 12 hours the sample stability and experimental reproducibility is well.The metabolites map of different strains was compared and analysed by PC A scoring figure.The results showed that the metabolites and demand between high-yield strains M and Co-5 strain were basically similar and located more closer to each other.The physiological metabolism differences between low-yielding strains Br-12 and other two strains were more remarkable,distant with the former two.In view of the metabolic levels of Br-12,M and Co-5 strains,the locus changes of bacterial cellulose production acted like "clockwise" and the metabolite map of different strains illustrated the low-yield,normal,productive strains changing process.The bacteria metabolic pattern and the genotype may be the major factor affecting the different metabolite map of different strains.Utilized load diagram to clarify the contribution of metabolites in the process of classification of strains.It turned out that the glucose,glucuronic acid,uridine,inositol make greater contribution to the classification of strains,indicated that these metabolites play vital roles in bacteria physiological metabolism and acid resistance.In this research the changes of different strains metabolites patterns caused by acid were compared and analysed.The results indicated that acid disturbance exert similar effects on Br-12 and M strains,pH4 sample and pH7 basic sample were separated.The samples get together when pH4,hydrochloric acid samples and metabolic pathways acid regulation samples were not in the same area.Showed acid disturbance can affect the physiological metabolism and the synthesis of product of Br-12 and M strains,while the mechanism of disturbances from byproduct of metabolic pathways and hydrochloric acid disturbance was different.The samples of different acid addition were in a different place under pH7 conditions,indicated the different hydrochloric acid exert different effect on the physiological metabolism of Br-12 strain.The samples of Co-5 strain by acid disturbance were decentralized under pH7.The samples of Co-5 strain did not get together and mixed with pH7 samples under pH4 indicated that Co-5 has a strong acid tolerance,this acid disturbance exerted little effect on physiological metabolism and the process of product synthesis.Metabolites load showed that glucose,glucuronic acid and ribose contributed greatly to bacterial metabolic pattern by acid disturbances.Extracellular glucose and ribose contribute to the effects of three bacterial metabolism imposed by hydrochloric acid,glucuronic acid may contribute to the classification of pH4 and pH7.The dispersion of Co-5 strain may due to its unique physiological characteristics and strong acid metabolic tolerance.Cluster analysis showed that bacterial fermentation metabolite map with different acid disturbances were divided into two categories,Br-12 and M class,Co-5 category.Br-12 and M Ph4,Ph7 were clustered together,while pH4 of Co-5 strain and pH7 samples did not distinguish.Overall,the impacts of metabolic pattern largely depend on the strain types,which made the great contribution to the cluster analysis.The acid environment also affects the changes of metabolites,which mainly affected the metabolic pattern of Br-12 and M-bacteria,Co-5 is insensitive.Acid disturbance affected the metabolic patterns of bacteria,thereby affecting its product synthesis.Compared with the control,acid disturbance exerted different infiuences on different strains.The five acid disturbances could increase production of bacterial cellulose of M strain and could significantly increase production of bacterial cellulose of Co-5 strain under pH7.However,the acid disturbances inhibited production of bacterial cellulose of Co-5 strain.For Br-12,the pyruvic acid and lactic acid,citric acid could increase its production of bacterial cellulose and other acids inhibited the production of bacterial cellulose.Overall acid disturbances affected the synthesis of bacterial cellulose,and mostly were beneficial to the synthesis of bacterial cellulose.Given the current study is mainly considering the fermentation environment and metabolic physiology of the strains,the molecular mechanisms of acid disturbance exert on cellulose synthesis needed to be further studied. |
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