Study On The Conditions Of Lf2 Bacillus Sporulation And Its Spore Germination

A bacterial strain Lysinibacillus fusiformis(Lf2) which has been proved to have the ability to degrade COD efficiently in domestic sewage has been separated by our laboratory. To further optimize the production and application process of the bacillus, the forming condition of the spore and the condition of it's spore germination are researched in this study.From the morphology of spore we can see that, the morphology has experienced three steps before 25h, firstly coccoid, then slender rod and finally short rod; after 25h, one end of the cell begins to expand, refraction gets more significant. The process of growth is similar to the traditional one, and the expanding trend of Lf2 bacillus develops into spore at last.During the progress of fermentation before optimization for Lf2 bacillus,0-9h stands up for lag phase,9-33h for log phase, after 33h for stable phase, no decline phase appears. The maximum number of Lf2 bacillus adds up to approximately 2.45�109cell/mL after 33h, the vegetative body about 2.03�109cell/mL at 21h,after which declines, and the spore about 2.30x109cell/mL at 41h, the spore number remains stable afterwards, the conversion rate reaches 94.3%.From the test of forming conditions optimization for spore of Lf2 bacillus, the spore number of Lf2 changes obviously at 37?, The maximum number is approximately 2.812�109cell/mL, which improves 22.26% comparing with that under normal conditions at the same time. The maximum number of spore is approximately 2.69�10 cell/mL at pH6, improving 16.96%. The maximum reaches 2.55�10 cell/mL when the concentration of H2O2 is 64ppm, improving 10.87%. The results of orthogonal test implies, the group 40?, pH5.5 and 72ppm effects significantly, the maximum reaches to 2.95�109cell/mL at 41h, improving 28.26% after optimization.From the condition optimization for the spore germination of Lf2 bacillus we can conclude, the initial pH5 effects most significantly, under which condition the offspring after germination steps into log phase ahead of 2-3h after optimization. The time that the offspring after germination enters into log phase constantly brings forward with the temperature rising, the offspring after germination enters into log phase ahead of 5h under 33?, ahead of 7h under 37?, no germination can be observed under 20?. Initial ORP has an obvious effect on the growth of the offspring after germination, when the initial ORP of medium is 15,50 and 85mv in different conical flask, the offspring after germination enters into log phase ahead of 6h,7h and 9h after optimization. The orthogonal test shows the group 34?, pH5.5 and 80mv takes the shortest time entering into log phase, which is ahead of 11h after optimization.