Optimization Of Fermentation Conditions For Marine Bacterium SH27 And Bio-control Phytophthora Sojae By Agents Mixed SH27 Strain And Organic Fertilizer

The fermentation condition of marine bacterium SH27 which isolated from coral producing the antimicrobial substances against the Phytophthora sojae was studied by media screening and its components orthogonal design, the cultural conditions single factor test and response surface methodology with Box-Behnken design. The results showed that the best medium for SH27 was GBE, its optimized formula were beef extract 10 g, glucose25 g, MgSO4 0.5g, KH2PO40.5g, distilled water 1000 mL.The optimized fermentation conditions were temperature 18 ℃, pH7.3, time 54 h, 2% inoculum, speed 180r/min, liquid volume 150/500 mL. The antimicrobial bandwidth of the SH27 culture filtrate against the Phytophthora sojae was up to 7.8mm by the optimized conditions. The main antibacterial substances proved to be protein substances which remains basical stability to temperature.The antibacterial activity of culture filtrate declined slightly when heated in water at40-100 ℃ for 60 min and 121 ℃ for 20 min. At the same time, SH27 antibacterial substances show some sensitivity to ultraviolet when irradiated for 3h, the inhibition zone reduced 0.33 mm.The growth-promotion result shows that the root activity, soluble sugar content and chlorophyll content and the apparent morphological indexes such as plant height, fresh weight, dry weight, root length of soybean was promoted significantly comparing to blank group when applying SH27 strain broth mixed with organic fertilizer and shell powder respectively as base fertilizer. The increasing order is SH27, Shell Powder+SH27, Organic Fertilizer, Organic Fertilizer+SH27. The result indicates SH27 has growth promotion on soybean and the growth promotion was greater when SH27 mixed with organic fertilizer and shell powder. Furthermore, the bio-contol Phytophthora sojae result also shows that the control efficacy was strengthened when SH27 mixed with organic fertilizer and shell powder respectively, the control efficacy are 52.09% and 43.91%. That is much more higher than SH27 group which is 37.26%. In conclusion, the control efficacy and growth promotion will be greater when SH27 mixed with organic fertilizer and shell powder which may be the appropriate matrix for making SH27 agents.