| Lecanicillium lecanii (Zimmermann.) is a worldwide entomogenous fungus, mainly infesting scale insects, whitefly, aphis. As a member of entomopathologic fungi, there is a great potential to be used as a biological agent to control the insect pests in agriculture crops and forests. In this thesis, strain V3.4505 of L. lecanii was employed to study the solid state fermentation kinetics of the fungus. The results will provide a reference for the dynamic monitoring and quality controlling for the fungal production in large-scale.The contents in this study are as follows:(1) The preliminary test was conducted for the five formula of culture medium for solid fermentation of L. lecanii. And a formula of culture medium was determined as the optimized one;(2) Under laboratory condition, the a series of factors that reflect the solid state fermentation kinetics of the fungus L. lecanii were measured. These factors included fungal biomass and spore production, and nutrition consumption, such as gross sugar, reducing sugar and nitrogen in culture medium in the procession of solid fermentation.(3) Under factory condition, biomass and spore production of the fungus L. lecanii were examined in solid fermentation. And the consumption of gross sugar, reducing sugar, and nitrogen in culture medium were measured.(4) Based on the test data, the kinetic model of the fungus were constructed by employing Logistic formula as to reflect a pattern of L. lecanii development and substrate consumption in the solid fermentation.The results show as follows:(1) L. lecanii V3.4505 was cultured on five different solid culture medium, and the spore production was examined, By comparing, the most optimized culture medium with spore production 9.6×10 (g/cm) for the fungal solid fermentation was chosen and which consists of 50% rice hull, 35% wheat bran,15% corn starch, and 50% water.(2) Under laboratory condition, the test results showed that of L. lecanii developed in three stages, that is slow growth phase, exponential phase, and stationary phase. The curves of biomass and spore production of the fungus shared a resemblance pattern, yet the differences lay in that the exponential phase of the former one lasts from 1.5 d to 6 d and rise from 3.2278 g/cm2 to 10.0219 g/cm2, the later lasts from 1.5 d to 9 d and mounted from 1.3688×107 /cm2 to 8.9012×107/cm2.The consumption of gross sugar and nitrogen well fitted with the three stages of the fungus development. When the fungus was in slow growth phase, the nutrition consumption was low, that is 3% and 6% respectively; when in the exponential phase, the consumption of the substrate by the fungus mounted aggressively, on the 6th day, the velocity of consumption of gross sugar and nitrogen reached 38% and 26% separately; when stepping into stationary phase 7.5d later, the consumption of gross sugar descended, and the velocity of gross sugar and reduce sugar stayed at no more than 3% and 6% respectively. Yet the peak of consumption velocity of nitrogen emerged in the first 3 d, which gets as much as 17%, after 3d the consumption descended, with the velocity of which staying no more than 5%.(3) Under large scale production conditions in factory, the development of L. lecanii V3.4505 also passed through three stages, slow growth phase, exponential phase, and stationary phase. From inoculation to 1.5d of cultivation, when the development of fungus was low, it was the slow growth phase; from 1.5d to 7.5d after inoculation, when the fungus grew very quickly, it was the exponential phase, during which the spore production ascended from 1.1690±107/gram to 4.745±107/gram; from the 6th day since inoculation, the fungus moved into stationary phase, and the consumption of substrate in culture medium became low.The consumption of gross sugar and nitrogen was well fitted with the three stages of the fungal development, when the fungus was in slow growth phase, the nutrition consumption was low, that is 9% and 10%respectively, and when in exponential phase, the consumption of the substrate by the fungus mounted aggressively, on the 7.5th day, the velocity of consumption of gross sugar and nitrogen reached 38%a nd 26% separately; when stepping into stationary phase 9d later, the consumption of gross sugar descended, the velocity of gross sugar and reduced sugar stayed at no more than 3% and 6%, respectively. Yet the peak of consumption velocity of nitrogen emerged between 1.5d and 6d, which got as much as 8%, and 6 days later the consumption descended, the velocity of which staying no more than 0.6%.(4) The data from experiments above were analyzed by using a software program Origin 7.5. The kinetic mathematic pattern and parameters thereof in the process of fungal fermentation were obtained. Under laboratory condition, the consumption pattern of the gross sugar and nitrogen aiming at biomass were St(total sugar)=31.879-1.4654(Ct-0.579); St(reducing sugar)=2.6553-0.0873(Ct-0.579); St(nitrogen)=0.1083-0.0018(Ct-0.579), respectively, and the degree of fitting thereof were 0.9825,0.8918 and 0.9013; the consumption pattern of the gross sugar and nitrogen aiming at spore production were St(total sugar)=28.845-1.4803(Ct-0.5108); St(reducing sugar)=2.4648-0.0862(Ct-0.5108); St(nitrogen)=0.1125-0.0037(Ct-0.5108), respectively, and the degree of fitting thereof were 0.8342,0.8168, and 0.7446. In the factory, the consumption pattern of the gross sugar and nitrogen aiming at spore production were St(total sugar)=36.569-3.1053 (Ct-1.369); St(reducing sugar)=9.0174-0.8467(Ct-1.369); St(nitrogen)= 0.1284-0.0036 (Ct-1.369), respectively, and the degree of fitting thereof were 0.9538,0.8565, and 0.8905.To summarize, no matter it was under laboratory condition or factory condition, the development of the fungus was in three stages, the slow growth phase, exponential phase, and stationary phase. Via quantitive description of the relationship between growth of the fungus, spore production and consumption of carbon and nitrogen source in the culture medium in the procession of solid fermentation of L. lecanii V3.4505, this study established kinetic pattern and obtained parameter of the pattern, with which the dynamic monitoring of relating index in the solid fermentation and quality controlling of each serial in the large scale production can use as a basis. This is significant to biological control by applying fungus as biological insecticides. |
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