Production Of Isaria Cateniannulata H-12-2 Sustained Release Agent And Biological Activity Detection Of Its Fermentation Products

Isaria cateniannulata H-12-2 is a common entomogenous fungs.It has a good contact killing effect on insect-sucking pests such as lepidoptera and acaridae.The biological activities of its metabolites have great application prospects in biological control and agriculture.In this study,we use Isaria cateniannulata H-12-2 spore powder as raw material to prepare a sustained-release agent,which changed the mode of direct spraying spore powder to the farmland.Then the biological activities of Isaria cateniannulata H-12-2 fermentation products were further studied.The main results of this research are as follows.1.In this study,we research the best addition amount of Isaria cateniannulata H-12-2spore powder and the optimal ratio of the sustained release agent and wall materials.The result shows:When the addition amount of spore powder is 0.1g/mL,sustained release agent particle size is uniform,with diameter of 1.86mm;conglomeration rate reaches to 96.85%;release rate is steady,and the release grade reaches to 66.99%at the 7th day.Too high or too low core ratio will both reduce the performance of the small ball.The encapsulation and release of Isaria cateniannulata H-12-2 spore powder by three kinds of encapsulation materials are different.Sustained release agent,made from embedding medium of 3%sodium alginate/0.5%gelatin/0.5%starch,compares with that made from embedding medium of 4%Sodium alginate or 2%Sodium alginate/2%gelatin,The small ball has the highest tolerance with the load-bearing capacity of 3.53g;drug loading capacity increases to 4.08×10⁹cfu/g;embedding rate increases to 93.78%.The encapsulation and release ability of Isaria cateniannulata H-12-2 spore powder with 0,10,20,30,40g/mL chitosan and sodium alginate sustained-release agent showed that the particle size,hardness and swelling rate of sustained-release agent were positively correlated with the concentration of chitosan.while the release rate was negatively correlated with the concentration of chitosan.With the increase of chitosan concentration,the spheroidization rate first increases and then decreases.When the chitosan content is 30 g/L,the highest spheroidization rate is 89.98%.The tolerance of chitosan/gelatin/starch microspheres was significantly lower than that of chitosan/sodium alginate microspheres,and the release rate was significantly higher than that of chitosan/sodium alginate microspheres.2.In this study,Isaria cateniannulata H-12-2 sustained release agent was optimized by adding carbon source,nitrogen source and surfactant to the original formulation.The results showed that the optimum amount of sucrose was 0.04g/mL.When the concentration of sucrose was 0.04g/mL,the release rate of sustained-release micro spheres to Isaria cateniannulata H-12-2 increased significantly to 82.90%on the tenth day.Excessive addition of sucrose leads to lower release efficiency and difficulty in pelleting.The optimum dosage of NaNO₃ was 6g/L,and the small dosage of NaNO₃ had no effect on the mechanical properties of sustained-release microspheres.The optimum concentration of Tween-20 as surfactant was15%.When Tween-20 concentration was 25%,the embedding rate decreased to88.76%.When Tween-20 was added at 20%,the release rate increased to 96.59%on the 10th day.3.Under laboratory conditions,production of different concentrations of Isaria cateniannulata H-12-2 fermentation,in 2,3,4 instar Myzuspersicae 10D.The results showed that the fermentation products of Isaria cateniannulata H-12-2 had certain pathogenic and lethal effects on Myzuspersicae.For aphids of the same age,the lethal rate increased gradually with the increase of the concentration of spore fermentation broth from 1×10⁷cfu/mL to11×10⁷cfu/mL.With the decrease of aphid age,the more sensitive aphids are to fermentation broth,the higher the mortality rate is,up to 74.36%.4.Under laboratory conditions,after Isaria cateniannulata H-12-2 liquid fermentation,the fermentation broth was diluted in proportion of 1:40,1:30,1:20,1:10 and 1:0.Then discharge to Triticum aestivum L.,Glycinemax（Linn.）Merr.,Daucus carota L.and Spinacia oleracea L.seedlings.The results showed that the inhibitory effect on Triticum aestivum L.,Glycinemax（Linn.）Merr.,Daucus carota L.and Spinacia oleracea L.was the most significant when the concentration of fermentation product was 1:40.Effect of seed germination rate after 7 days of cultivation:Spinacia oleracea L.>Daucus carota L.>Triticum aestivum L>Glycinemax（Linn.）Merr.Effects on stem length:Spinacia oleracea L.>Triticum aestivum L.>Glycinemax（Linn.）Merr.>Daucus carota L.The effects on root length were Spinacia oleracea L.>Triticum aestivum L.>Daucus carota L.>Glycinemax（Linn.）Merr.The effects on root weight and total weight were Spinacia oleracea L.>Triticum aestivum L.>Glycinemax（Linn.）Merr.>Daucus carota L.In general,Spinacia oleracea L.is more sensitive to the stress caused by the fermentation products of Isaria cateniannulata.And the dilution in the range of 1:0¹:40,the higher the concentration of stress gets stronger.