Investigation And Application Of Dextranase And Dextransurase And Dextran Production From Co-culture OfLeuconostoc Mesenteroides And Penicillium Aculeatum

This study was based on Penicillium aculeatum F1001 producing dextranase and Leuconostoc mesenteroides-0326 producing dextransurase, while Leuconostoc mesenteroides fermentation products is inducer of Penicillium aculeatum producing dextranase, meanwhile dextranase can promote dextransurase produced by Leuconostoc mesenteroides. According to different products, we designed responsible experiments to obtain targeted enzymes. At the same time,the related parameters and molecular in the fermentation process was determined to find some rulesabout co-culture fermentation producing enzymes.The study firstly optimize fermentation conditions for dextranase-producing by Penicillium aculeatum. The fermentation conditions with medium loading, peptone and Dxtran 70 content was optimized using a Box-Behnken design with response surface methodology. The optimal fermentation conditions were determined as followed: Peptone 3 g/L, Dextran 70 14 g/L, medium loading of 85 mL/250 mL. Which under these conditions dextranase activity can reach 453 U/mL and 88% improvement over before. The changes of dextranase activity, pH, protein content in the fermentation process verified that dextranase activity reaches the summit at 84 h with the maximum protein content and pH 3.9.And then explored the Penicillium aculeatum and Leuconostoc mesenteroides co-culture fermentation including spontaneous fermentation and sequential fermentation producing dextranase. It paid more attention for sequential co-culture fermentation method. To determine sequential co-culture fermentation conditions, the Design Expert 8.0.6 software was used. The results was as followed.The optimum value of temperature at 28℃, fermentation time for 84 h, inoculum volume of 3%, and initial pH 4.5 were determined. Maximum dextranase production of 468 U/ml was predicted by co-culture of Leuconostoc mesenteriodes and Penicillium aculeatum under the optimum process condition. Process parameters such as were pH, protein content and the reducing sugar as well as Leuconostoc mesenteroides morphological changes were measured and observed. When dextranase highest enzyme activity, pH value of 5.2, low sugar content and high protein content.Penicillium aculeatum and Leuconostoc mesenteroides co-culture fermentation producing dextransurase was also researched. The results showed as followed. The initial sucrose concentration is 2%, Penicillium aculeatum inuculumed in fermentation liquid after Leuconostoc mesenteroides fermented 24 h, supplemented 20% sucrose 5 times to make a final concentration of 11% during fermentation and pH was adjusted to 6.8-7.5 and 6.0-6.5 respectively at the first two stages.At the end of the study, dextran molecular weight changed in co-culture fermentation was made preliminary research. Dextran molecular weight reaches a maximum at fermentated 60 h and then decreases rapidly to 5036 Da during spontaneous fermentation. While in sequential fermentation, dextran molecular weight chaned obviously after Penicillium aculeatum inculumned for 4 h, then the molecular weight is between 5000 Da and 10000 Da. It containing fructose, glucose and malt in fermentation liquid detected by amino column. Compared with fermentation procuding dextran and type sample dextran by using infrared detector, found that the functional group absorption peak position has not changed, which indicated that dextran functional groups has nothing to do with the size of the molecular weight and fermentation method.