The Influence Of Stirring Method To Structure-activity Relationship Of Exopolysaccharide By Fungi

The objective of this study was to investigate the effect of stirring effect on theproduction of exopolysaccharides (EPS) from three enthomopathogenic fungus, Pycnoporussanguineus, Abortiporus biennis and Ganoderma cantharelloideum in a stirred-tank reactor(STR) and in an airlift reactor (AR). The single factor experiment was adopted to optimal thesubmerged culture medium for EPS production in shake flask, and the morphological changesof mycelium was studied during the fermentation process in the tank; Secondly, the molecularcharacterization of EPS was discussed by means of sepharose gel chromatography, gascharomatography, infrared chromatography(IR), thermogravimetric analysis(TGA) and congored experiment. Thirdly, the antioxidative activities of the EPS was assayed by salicylic acidmethod and DPPH in vitro. Finally, to research the application of EPS of Abortiporus biennisin tobacco industry, the effects of supplement of EPS in the type and content of flavoringmaterials was investigated.The results suggested that the optimal conditions for EPS production of Pycnoporussanguineus, was as follows: cultivation cycle8d, glucose and soybean meal. Under theoptimal culture conditions, STR was more conducive to the formation of the mycelium pelletwith uniform and density, and maximum EPS growth (2.92g/L) was after4d of cultivation ina5-L stirred-tank reactor, whereas, EPS yield was maximal (2.11g/L) after2d. Then, IRspectral analysis of the purified EPS revealed prominent characteristic groups. Dye-inclusionstudies with Congo Red indicated that each EPS existed in a random coil conformational state.The weight-average molar masses of EPS of STR and AR were determined to be462.97kDaand55.00kDa, respectively. Furthermore, monosaccharide composition analysis indicated thatpurified EPS from STR was mainly composed of mannose and glucose, while purified EPSfrom AR mainly composed of glucose. Furthermore, TGA indicated the degradationtemperature (Td) of the EPS from STR (152oC) was higher than that of EPS from AR (116oC). In addition, the antioxidant activities of the polysaccharides from different bioreactorswere investigated. EPS from STR exhibited the highest antioxidant ability than EPS from AR,which might be attributed to the monosaccharide composition in the EPS group.The results suggested that the optimal conditions for EPS production of Abortiporus biennis, was as follows: cultivation cycle8d, lactose and tryptone. Then, IR spectral analysisof the purified EPS revealed prominent characteristic groups. Dye-inclusion studies withCongo Red indicated that each EPS existed in a random coil conformational state. Theweight-average molar masses of EPS of STR and AR were determined to be22.071kDaå'Œ17.301kDa, respectively. Furthermore, monosaccharide composition analysis indicated thatpurified EPS from STR was mainly composed of glucose(51.45%) and mannose(30.30%),while purified EPS from AR mainly composed of mannose(53.24%) and glucose(38.48%).Furthermore, TGA indicated the Td of the EPS from STR (115oC) was similar to EPS fromAR (100oC). In addition, the highest·OH and DPPH radical scavenging activity of EPS fromSTR were16.73%and10.88%, while the highest·OH and DPPH radical scavenging activityof EPS from AR were14.62%and13.15%. The EPS of STR and AR showed a semblablestructure and antioxidant activities, which might be due to the molecular weight, thermalstability was relatively close, and that monosaccharide composition in the EPS group hadsmall differences. With application of EPS in tobacco production, the contents of ketones,aldehydes and furans decreased significantly, while the contents of ester and lactone andphenol increased in the cigarettes. The treatments with EPS could reduce stimulation ofsmoking, and improve the aroma of cigarette to ameliorate the quality of smoking.The results suggested that the optimal conditions for EPS production of Ganodermacantharelloideum was as follows: cultivation cycle8d, glucose and peptone. Two groups ofEPSs (designated as Fr-I and Fr-II) were isolated by gel filtration chromatography usingSepharose CL-6B. The weight-average molar masses of the Fr-I and Fr-II were determined tobe627.672kDa and74.563kDa, respectively. However, the average molecular weight of EPSfrom AR was40.567kDa. Furthermore, monosaccharide composition analysis indicated thatFr-â… and Fr-â…¡from STR was mainly composed of mannose(81.56%) and glucose(41.83%),respectively, while purified EPS from AR mainly composed of glucose(97.34%). In addition,TGA indicated the Td of the F-â… and F-â…¡(215oC and180oC) was higher than that of EPSfrom AR (101oC), which might be due to the molecular weight and mannose content were thehighest. Finally, the antioxidant activities of the polysaccharides from different bioreactorswere showed up good antioxidant activity in vitro, but weren’t acted out a certain regularity.So, the relationship of the structure and activity of EPS is still not clear.