Study Of Mutation Breeding And Fermentation Process For One G.rosea Strain

G.rosea is an important biocontrol strain which had strong destroy effects toBotyfis cinerea and also could parasitize many kind of plants pathogenic bacteriumsuch as Rhizoctonia solani. It had better effects to prevent such as soya beansclerotium disease and tomato gray mold disease. The purpose of this paper is to get astrain of high sporulation quantity and bacteriostatic activity, and use that inducedstrain for fermentation, to research for the optimal fermentation conditions.G.rosea UY-38was used as the original strain. Various single-factor andcompound factor mutagenesis methods were used to mutagenize the G.rosea UY-38,including UV, NaNO2, temperature and temperature-NaNO2. The best mutagenesistime has been found in this research, which is expressed as follows: UV irradiation is90s;50℃induced time is4min;0.1mol/L sodium nitrite mutagenesis is4min; thecompound mutagenesis of temperature and0.1mol/L sodium nitrite is that50℃induced for the first4min, and then0.1mol/L sodium nitrite irradiated4min.According to the sporulation quantity firstly and bacteriostatic activity secondly, thefour induced strains of UV-3, TR-5, NS-2and TN-1are selected, and their spores’quantity increased1.54times,1.11times,0.91times,1.16times, respectively.Compared with the original strain, The induced strains have better bacteriostatic effectand stable biological character. In the experiment of the inhibition of gray moldmycelial inhibition, the spore concentration was1×105spore/ml, bacteriostatic rate canreach80%in the fifth day, and bacteriostatic can be100%when cultivate eight dayslater. So, the UV-3was chosen as the solid-state fermentation strain.In the experiment of solid-state fermentation, through the single-factor research,we found three main factors: material thickness、hole density and initial water content.Then the solid-state fermentation conditions were optimized by response surfaceexperimentation and Box-Benhnken model. Results showed that the best fermentationconditions were: cultivation temperature24℃, initial pH7, material thickness3cm,hole density on fermentation reactor surface is0.74%, initial water content is150%. In this condition, the best yield of G.rosea sporulation was8.53×109spores/g mediumand the fermentation period was10days.