Study On Insecticidal Effect Of Paecilomyces Cicadaes

Paecilomyces cicadaes(PC) is a precious Chinese herbal medicine with high pathogenicity.It is significant to study the virulence of ogenic fungi in the biocontrol field. This thesis is to study the insecticidal effect of PC to aphides and Plutella xylostlla.All of the 8 strains of PC used in this thesis have different insecticidal effect.One of the strains, GZDXIFR4611,has the highest insecticidal function and its insecticidal rate could reach 88.7%especially in spore liquid medium.Study of four different enzymes in PC including chitinase,proteinase,lysozyme and esterase indicates GZDXIFR4611 esterase has a higher enzyme activity then others,hence,shows us the correlation between PC's esterase and virulence.In order to further research the relationship between PC esterase and insecticidal effect, we optimize the producing conditions of esterase,thereby raising the yield.By purifying the production,we got a relatively pure substances which was used in the insecticidal experimental again.The recipe of the optimal liquid medium used in selecting strains is soluble amylum(10g·L-1_-),yeast extract paste(7.5g·L-1),K₂HPO₄(0.35g·L-1), MgSO₄.7H₂O(0.35 g·L-1).Indicated by the research,the optimum incubation time is 48h, the optimum reaction factors of PC's esterase proves at PH=6.5,40℃,40 minutes with the half-life is 58 hours at normal temperature(25℃),and the enzyme remains stable at 40℃. Crude enzyme was salting out by 40—70%ammonium sulfate and filtrated by sephadex G-50 gel,Collecting the high active tubes and filtrated again by sephadex G-100 gel.In the experiment,the yield rate reaches 20.4%and the purification times is 8.05.The insecticide experiment with enzyme obtained at different stages tells us the enzyme purified with Sephadex G-100 has the highest insecticidal effect,the insecticidal rate could reach 86.7%, and indicates PC esterase is endowed with high virulent property.Based on the enzyme activity experiments of chitinase,proteinase,lysozyme among 8 strains of PC,we select GZDXIFR3716 as the highest activity strain.We also do some studies on enzyme's yield condition.The incubation time for the highest concentration of hitinase,proteinase,lysozyme in the GZDXIFR3716 liquid medium are 48h,60h and 84 h respectively;and the optimal reaction temperature are 50℃,40℃and 40℃in that order; the optimal reaction pH value are 6.0,7.0 and 5.0 in that order.