| Western flower thrips Frankliniella occidentails（Pergande） is one dangerous pest worldwide. It spread quickly and led to local outbreak after it was found in China in 2003, which has caused great damage to crop production and has become an important invasive pest in our country. Western flower thrips can not only reduce the output by feeding the juice, but also transmit various viruses which cause greater loss. Nowadays, with the concerns of pesticide residues, food safety, environmental pollution and insecticide resistance, biological control of western flower thrips is becoming more and more important. Beauveria bassiana as a safe and pollution-free pest fungi, has good control effect against western flower thrips, it has been developed into various dosage forms for field control. Choosing the isolate XJWLMQ-32 as the tested strains, the author optimized the liquid-solid biphasic fermentation process of B. bassiana. Firstly,in order to screen one of the most effective method for rejuvenation, the degraded strains were selected to test with four methods by comparing the number of conidia and LT50. Then, the author optimized the liquid and solid fermentation culture to determine the optimal production technology of liquid-solid biphasic fermentation. Finally, the culture was amplified using fermentation tank with a size of 7L by optimizing fermentation conditions which can improve the quality of the fermentation broth, thus improving spore production of solid fermentation. The results may provide theoretical and practical basis for large-scale production of B. bassiana strains. The major results are listed as follows:The B. bassiana strains XJWLMQ-32 through laboratory screening has efficient pathogenicity to Frankliniella occidentails, however, the strains’ degradation is very serious after subculturing 8 generations on solid sporulation medium. Carrying out rejuvenation experiments for the 8th generation degraded strains using four different methods, the results showed that, after five generations of continuous rejuvenation, insect powder of Frankliniella occidentails rejuvenation method had the best sporulation and virulence recovery result, the number of conidia was 9.11×108conidia/cm2, the LT50 was 2.87 d, the corrected cumulative mortality of Western flower thrips on the fifth day was up to 90%;After colloidal chitin medium rejuvenation, the LT50 of the strains was 3.12 d, the virulence improvement rate of each generation is moderate and stable; after pupa powder rejuvenation, the conidia had the highest number, but the virulence improvement rate was lowest and volatile; after the cicada medium rejuvenation, sporulation and virulence recovery were less effective. Adding the right amount of insect powder and colloidal chitin into the sporulation medium has better result to sporulation and virulence recover of degraded strains and has good stability, the proportion of virulence recover reduced to 11.45% from 13.39%, the improved proportion of sporulation reduced to 34.66% from 40.93%, only decreased 6.27%. Taken together, adding the right amount of insect powder and colloidal chitin into the sporulation medium has better result to sporulation and virulence recover of degraded strains and has good stability.The strain liquid fermentation conditions were optimized using Plackett-Burman experimental design and response surface methodology. The results showed that temperature, volume of liquid, rotate speed and initial conidia concentration were the main factors on mycelium mass. The change of p H within certain limits had less influence on this strain of liquid fermentation. Without considering p H, when the fermentation conditions of temperature, volume of liquid, rotate speed and initial concentration were 27.08℃, 47.72 m L/250 m L of triangular flask, 205.45 r/min, and 1.122×107 conidia/m L, the maximum mycelium mass was produced after 48 h of fermentation. Using the culture conditions to produce conidia, the mycelium mass obtained was about 14.769 g/L, which was consistent with the predicted biomass. After the solid state fermentation, the yield achieved about 20.16 g/kg and 1.84×1011 conidia/g.Taking the number of strains’ sporulation as indicators, using single factor test and orthogonal test method for screening a strains’ solid fermentation substrate, and optimize its solid culture conditions. The results showed that: using the wheat bran and rice husk as a solid fermentation substrate, adding 0.3%KH2PO4, 0.1%Mg SO4·7H2O, 0.1%NH4NO3 into the substrate and mix, keeping the ratio of wheat to rice as 4:1, the ratio of material to water 3:1, the inoculation amount of fermentation broth is 30%, using a 15cm×30cm preservation bags for charging material, placed in 26℃ incubator, after darkness closed culture for 3d, then light bag culture（light intensity 2500lx）for 5d, based on those conditions above, the obtained number of strains’ sporulation by this culture method was up to（18.30±1.58）×109conidia/g, which was significantly higher than the number of strains’ sporulation before optimization.Take the strains’ biomass in the fermentation broth as indicators, optimize the fermentation parameters of 7L fermenter, and carry on the amplifier culture of the strains XJWLMQ-32. The results showed that, after a shake flask primary fermentation the strains was inoculated into the 7L fermenter for the secondary fermentation and adjusted the p H of broth to 6.5 using Na OH / HCl, hold the rotating speed of the fermentation as 200r/min, aeration as 6L/min, fermentation time as 32 h, then inoculate the fermentation broth on a solid matrix for spore culture. By comparison, number of strains’ conidia has increased compared with shake flask fermentation; the number of contained spores was significantly higher than shake flask fermentation which reached to（2.08±0.18）×1011conidia/g. |
