Optimization Of Fermentation Process Of Strain JI6 And Its Growth-promoting Effect On Ginseng

The laboratory has obtained a strain of bacteria JI6 from ginseng rhizosphere soil.By measuring the growth-promoting indicators of strain JI6,it was found that it had the potential to promote plant growth.In order to make strain JI6 better used in ginseng cultivation,the fermentation process of strain JI6 was optimized by single factor optimization and response surface test,and the optimum medium formula and culture conditions of strain JI6 were obtained.Through the determination of adsorption carrier,protective agent and wetting agent,the optimum formula of strain JI6 was obtained,and its growth promoting application effect was studied.The test results are as follows :1.The indoor growth-promoting indexes of strain JI6 were determined.The results showed that strain JI6 had the ability to fix nitrogen,dissolve phosphorus,dissolve potassium and produce IAA.The seed germination test in petri dish further determined that the seed bud length treated by strain JI6 was better than that of the water treatment group,which was 42.76 % higher than that of the water treatment group.2.The strain JI6 was identified as Pseudomonas thivervalensis by morphological characteristics,physiological and biochemical indexes and 16 S r RNA sequence alignment.The optimum medium formula of strain JI6 was optimized by response surface method : sodium citrate 1.79 %,yeast extract 1.99 %,potassium chloride 0.32 %,magnesium sulfate 0.11 %.The optimum culture conditions of strain JI6 were determined by single factor test as follows :temperature 30 °C,p H 7,inoculation amount 4 %,rotation speed 180 rpm and culture time 30 h.3.Preparation of microbial agent : The best carrier,protective agent and wetting agent of the strain were screened by plate counting method,and the optimum dosage was determined.The results showed that the optimum carrier of JI6 was diatomite 5 %,wetting agent was polyethylene glycol 4 %,and protective agent was kaolin 1.5 %.The microbial agent was placed at 28 °C,4 °C and 40 °C for 6 months to determine the shelf life.The results showed that the storage effect was the best at 4 °C.The national standard of the bacterial agent was determined,and the infiltration time was 94 s.The suspension rate was 73.26 %.p H 7.3;the fineness is98 %;the mixed bacteria rate was 0,and the results met the standard requirements.4.The effect of JI6 on the growth of ginseng was determined by field planting test.Compared with the control group,the root weight,main root length,main root diameter and yield increase rate were significantly higher than those of the control group.The average weight was 58.5 g,and the yield increase rate was 38.72 %.It shows that the application of microbial agents can promote the growth and development of ginseng.5.The colonization of strain JI6 in ginseng root,stem,leaf and rhizosphere soil was studied by double antibody labeling method.The results showed that strain JI6 could be colonized in ginseng rhizosphere soil,and the strain could still be detected at 90 d,but it could not be colonized in all parts of ginseng.The results of ginseng-related defense enzyme genes showed that the expression of five related defense enzyme genes was up-regulated after treatment with strain JI6,and reached a peak within 5-9 days;the determination of rhizosphere soil enzyme activity showed that the microbial agent treatment could regulate the soil enzyme activity level during the growth period of ginseng,and the soil enzyme activity increased at different growth periods.The determination of rhizosphere soil microenvironment can improve the richness and diversity of bacteria and fungi in soil under the treatment of microbial agents,change the variation of microbial composition during the growth of ginseng,improve the abundance of beneficial bacteria to ginseng growth,and reduce the abundance of harmful bacteria.For the effect of the strain on the content of ginsenosides and the expression of synthetic genes,the content of ginsenosides could be increased by high performance liquid phase detection.The content of ginsenosides in the JI6 treatment group was 24.46 % higher than that in the water control group,and the difference was significant.For the effect of gene expression,the results showed that the expression of three saponin synthesis-related enzyme genes was up-regulated.In summary,strain JI6 has the potential to promote plant growth and can colonize ginseng rhizosphere soil,up-regulate the expression of defense enzyme genes and regulate the changes of community in ginseng rhizosphere soil.Promote the growth and development of ginseng,increase ginseng yield and saponin content.