Preliminary Study On Preparation Of Bacillus Megaterium Agent

Microbial agents can improve the physical and chemical properties of secondary salinized soil,improve microbial activity,play a role in remediation of the soil,and have caused widespread concern in recent years.A strain of Bacillus megetarium NCT-2 with high ability of degrading nitrate-nitrogen in soil was selected as the research object.After optimization of its industrial production medium,freeze-dried and microcapsuled agents were invented.The two formulations were compared with the original liquid agent.The main research results are as follows:1.Lactose 15 g/L,Soybean peptone 5 g/L,KH₂PO₄ 0.5 g/L,MnSO₄·H₂0 0.05 g/L were used to replace the original culture medium components with cheaper carbon and nitrogen sources.This culture medium can increase the number of viable cells to 1.25×10¹¹ CFU/mL,and the cost is 89.6%of the original culture medium.2.The optimum freeze-drying conditions were 5000 r/min,10 min.The freeze-dried protective agent was optimized by single factor analysis and response surface methodology.The sucrose concentration was 4.51mg/g,trehalose 0.90 mg/g and glucose 9.60 mg/g.The survival rate of NCT-2 was 91.8%,which was six times higher than the previous optimization.3.The results showed that the optimum conditions were as follows:wall material chitosan:maltodextrin=1:1?w/w?,inlet air temperature150.0?,feed rate 1000 mL/h,in which the microcapsules showed the best product properties.4.The results of scanning electron microscopy?SEM?showed that the microcapsules had the best quality and the empty capsules were the least.Meanwhile,the production cost of microcapsule was moderate,and the viable count was higher than that of GB 20287-2006 for 4 weeks and 8weeks storage,comparing with freeze-dried powder and liquid agent.