Optimization Of Fermentation Conditions Of Bacillus Velezensis Strain TCS001 And Its Bio-control Effect

In this paper,in order to provide experimental foundation for the development and application of the microbial pesticides TCS001,we studied the physiological and biochemical properties andsystematic taxonomic status of the strain TCS001,which was isolated from the Bohai Sea mud.We explored the optimal fermentation conditions of the strain TCS001,revealed its antibacterial activity,bio-control effect and the preliminary antibacterial mechanism.1.The strain TCS001 was identified through morphology,physiological and biochemical tests combined with molecular identification technology of gene gyrA;the growth curve of TCS001 was determined by surveying and evaluating the value of OD₆₃₀30 of fermentation liquid at different culture period.The results showed that TCS001 was a Gram-positive bacterium,Bacillus velezensis.Bacillaceae,and it's growth phase was 0-52 h,the logarithmic growth phase was during 10-20 h.2.The antibacterial spectrum of TCS001 was detected by plate sputum method.It was found that TCS001 had broad-spectrum antibacterial activity,and it had the strongest antibacterial activity against Botrytis cinerea?BC?,which was 84.12±0.19%.The fermentation conditions of TCS001 were optimized by single factor test and response surface analysis.The optimum conditions for optimization were beef extract 4.0 g,shaking speed 164 rpm,temperature 25°C.The inhibition rate on BC of 20-fold dilution fermentation filtrate was 89.27±2.06%under the condition.3.Different concentrations of TCS001 fermentation filtrate were prepared to detect the inhibition rate on BC mycelial growth and spore germination.Plant spray method was used to investigate the bio-control effect of TCS001 fermentation broth on cucumber gray mold and cucumber powdery mildew.The results showed that TCS001 fermentation broth had strong inhibitory effect on BC mycelial growth and spore germination.Among them,5-fold dilution had the strongest inhibitory effect,and the inhibition rate on BC mycelial growth and spore germination was 96.24±0.86%and 98.05±2.67%,respectively;TCS001 fermentation broth can significantly inhibit the growth of cucumber gray mold,the control effect is 74.74±3.46%,and can significantly reduce the cucumber powdery mildew disease index 75.56%.4.The bio-control mechanism of TCS001 was discussed.The effects of TCS001 on mycelial growth and spore morphology of BC were observed under light microscopy and scanning electron microscopy.The defense enzyme activities of cucumber plants treated with TCS001 fermentation broth were also examined.The results showed that TCS001 could lead to the broken of hyphae and inflated of spore buds of BC.