| Abstract: |
SUMMARYNowadays, all attention looks towards applying several control methods which cause a remarkable reduction of pests and limit their multiplication under their threshold level of infestation. Thus, the biological control must be widespread but chemical one Microbial degradation of insect cuticle components such as protein and chitin components, and production of cuticle degrading enzymes particularly proteases have captured the world wide attention of biocontrol studies. But unfortunately the degradatives aA review of previous works on proteolytic fungi and chitinolytic bacteria and their role in biocontrol of insects is given in the introduction. The results obtained can be summarized in the following:1- Twenty nine fungal species belonging to twelve genera were recovered on dilution plates, containing casein or insect protein as the sole nitrogen sources in the media from different Egyptian soil and insect samples at 27oC.2- Twelve bacterial isolates were recovered on dilutions plates, containing colloidal chitin as the only carbon sources in media, from Egyptian soil and insect samples at 27oC. The relative chitinolytic activities and growth of the isolated bacteria under3- The relative proteolytic activities of the isolated fungi at 30oC revealed that Paecilomyces violaceae followed by T. harazianum, Paecilomyces varioti, T. viride, A. fumigatus, A. niger, T. Koningii, A. Flavus, A. nidulans, P. chrysogenum and A. oryzae4- It was obvious that Paecilomyces violaceae possessed the highest protease production on both tested media under mesophilic conditions. Hence this isolate was chosen for further study.5- Optimization studies revealed that, an incubation period of 6 days was found to be sufficient for reaching the maximum protease production and biomass yield by tested fungi as grown at 30oC and pH 5.0.6- The optimization of culture conditions appeared that the Paecilomyces violaceae produced protease of high productivity as grown in 50ml aliquots of the basal medium in 250ml Erlenmeyer flask and inoculated with 6-days old seed culture under static cond7- Among the tested carbon source, glucose was found to be the most suitable for maximum protease production and growth rate of selected isolate at concentration 3.0% (w/v).8- On equal nitrogen basis, among the test nitrogen sources, casein and insect protein were found to be the suitable nitrogen sources or maximum protease production at concentration 1.5% (w/v). On the other hand, the experimental organism grows luxuriantl9- Phosphate salt (KH2PO4) exerted stimulatory effect on both growth and proteolytic activity of tested fungus. Maximal growth and protease production were obtained in the presence of 1.0 KH2PO4 (g/L).10- The synthetic of protease and growth of Paecilomyces violaceae was found to be affected by the presence of magnesium sulphate and potassium chloride levels in both culture media. The maximum biomass and protease production were obtained in the presenc11-On studying the effect of metal ion and some inhibitors on the growth rate and protease production by Paecilomyces violaceae, it was found that, the addition of Fe+2 and Zn+2 ions individually to the tested media had profound effect on growth and prote12- The addition of some B-group vitamins to the culture media had no significant promoting effect on both growth rate and protease activity of selected organism.13- Physicochemical properties of protease and the reaction conditions affecting the hydrolysis of insect cuticle protein were studied. Maximum protease activity was obtained by using 10 mg substrate/ reaction mixture in citrate phosphate buffer at pH 5.014- The stability of crude protease was also investigated. The crude protease of selected fungus was found to be thermos table and could tolerating heating without loss of activity at 35 and 40 oC during 120 and 90 minutes, respectively. The same enzyme w15-On studying the influence of metal ions and inhibitors on enzymatic reaction and protease activity, the data appeared that, enzyme was slightly activated by Ca+2 and Mg+2 ions. However Mn+2, Fe+2, Zn+2 and EDTA had an inhibitory effect on protease acti16- An attempt was conducted to use this selected fungus (Paecilomyces violaceae) as a biocontrol agent against pink boll worm insect conidia and metabolites of Paecilomyces violaceae were studied with three different treatments (mixed conidial suspension17-The results of the biocontrol test done on the experimental insect revealed that, on larval and pupal mortality the tested fungus caused highly significant effects with all treatment on the larval diet. On the other hand, in the adult emergence and def18- It was obvious that the pupal and larval durations were significantly affected with all treatments.19- Moreover, results of effects on fecundity and fertility showed that the three tested treatments caused significant effect on the fertility and hatchability percentage.
|
|
|