Isolation And Chraterization Of Chaetomium And Optimization Of The Fermentation Conditions

Agricultural production decrease greatly because of crop diseases and pests.Biological control of plant diseases and pests has many advantages, such as long timeeffect, the control effect remarkable, good safety and not causing resistance.Therefore, biological control is considered to be the main control method in the futureagriculture production. Chaetomium is one of the most important biological controlstrains, which has the ability to serve as a good strain in biological control agents. Itinhibit plant pathogen through competition effect, induced systemic host resistanceand producing antibacterial metabolic substances.This research is mainly about screening Chaetomium which has the function ofbiological control from several specific environments and preliminary studying itsfermentation conditions of metabolites. In this experiment, separation medium is usedto screen the strains which have cellulose degradation ability from the samples. Wefound that there were eight Chaetomium strains through examining microbialmorphology using microscope and named G12, G14, G15, H6, H10, I3, I4, I5.Through molecular identification of microbial species using ITS sequence analysis,we found the similarity of eight strains with Chaetomium were over94%. Throughthe pathogen confrontation experiment, we found that strain H10had good ability ofbiological control on Sclerotinia sclerotiorum, fusarium oxysporum, and Rhizoctoniasolani, Its growth rate was also fast, under the condition of28°C,4d. It can be fullof9cm plate and began to produce dark perithecium after cultured for3days.The cellulase activity of Chaetomium H10strain was measured every day, whichwas induced by enzyme production medium. After culturing for two days at28°Cand170rpm, the activity of FPase, exoglucanase, endoglucanase, and β-glycosidaseachieved the maximum of0.55U,0.35U,0.47U,0.47U respectively. Then wecultured H10, under the condition of28°C,170rpm in PDB liquid fermentation andfound that, in the process of the liquid culturing strain H10hardly to producereproductive structure such as perithecium and ascospore. Lacking of oxygen andattachments, mycelium cannot produce reproductive structure. The broth isconcentrated under the condition of0.1MPa,40°C. The effect of different pH, timeof fermentation on antibacterial ability of metabolites was studied. The resultsshowed that when the initial pH is6.5, the antibacterial rate is maximum to47.32%.After13days’ fermentation, the antibacterial ability of metabolites reached to themaximum at43.11%. We also found that metabolites production may also be affectedby the dry weight of the mycelium.Although this study was a basic research, it expanded the resources of the biological control strains, and confirmed that the strain H10had the potential tobecome excellent biological control agent. This research lay the foundation for theindustrialization production of biological control agent.