Screening Of Efficient Phosphorus Solubilizing Bacteria In Soil And Optimization Of Their Fermentation Process

Phosphate solubilizing bacteria(short for phosphorus bacteria)are a group of bacteria with strong solubility in soil.Phosphorus bacteria can make soluble phosphates into soluble phosphide can be used into soil,it is also called the phosphate solubilizing bacteria,Phosphate solubilizing bacteria play their own biological characteristics mainly by producing various enzymes or acids,and phosphate solubilizing bacteria play an indispensable role in the recycling of phosphorus resources,because phosphorus bacteria can convert insoluble inorganic phosphorus into soluble phosphorus,improving the phosphorus utilization rate of crops,so it is widely used in the production of microbial fertilizer.Practices have proved that phosphorus bacteria can increase the yield of wheat,sweet potato,soybean,rice and other fruit trees,such as apples and peaches.The phosphate solubilizing bacteria commonly is used in agricultural production,including phosphorus solubilizing bacillus,commonly known as the big spore phosphorus bacteria.Furthermore,other Bacillus and Achromobacter,Pseudomonas and so on are used in agricultural production.In this experiment,efficient phosphorus solubilizing bacteria were isolated from rhizosphere soil.strains isolated from soil by using plate dilution method to preliminary screening,according to the ability of solubilizing transparent circle diameter and colony diameter ratio determined strain solution of inorganic phosphorus and organic phosphorus,and then through the liquid shaking flask,by using Mo-Sb colorimetric assay to determine effective phosphorus in the fermentation supernatant,so as to further determine the phosphate solubilizing ability of isolated strains.The experiment screened 1 strain with high degradation ability of organic phosphorus bacteria which in the egg yolk medium can produce P loop solutions obviously,decomposition of organic phosphorus was the strongest,the ratio of D/d is 4,the lecithin liquid culture medium 5days,effective phosphorus in fermentation supernatant reached a maximum value of 54.21mg/L is 45 times of the control group,can see the solubilizing effect significantly.The strains were identified by a series of tests such as morphological characteristics,physiological and biochemical characteristics and 16 S rDNA sequence analysis.The bacterium was preliminarily identified as Bacillus megaterium.Single factor experiment and response surface method were used to optimize the fermentation medium and the optimum fermentation conditions for Bacillus megateriumBM2.The experiment showed that the optimum growth condition of Bacillus megaterium BM2 was optimized,the optimum growth temperature was 32?,and the optimum growth pH was 7.2.The best carbon source for the strain fermentation medium was soluble starch,the best nitrogen source was soybean powder,the best inorganic salt as potassium dihydrogen phosphate.Using the central composite experimental design and response surface analysis was carried out according to the actual value,to determine the optimal fermentation conditions for 48.85g/L of soluble starch,soybean meal 19.67g/L,p H 7.2,the number of spores of the design theory is 43.16×108cfu/m L,the number of spores measured is 41.29×108cfu/m L,and the theoretical value of the gap is very small.The optimum fermentation temperature was 34?,the optimum inoculation amount was 3%,the optimum fermentation time was 32 h,and the optimum liquid loading was 60mL/250 m L.In order to improve the biological stability of Bacillus megaterium,through the optimization of the immobilization of Bacillus megateriumBM2,determine the best immobilized carrier and crosslinking agent,the best carrier for the concentration of 4% sodium alginate,the best crosslinking agent of 4% calcium chloride,nitrobacteria in 10%,when cross-linking time where 24 h strains can maintain its the best activity,to achieve the best effect.Experiments were carried out on Arabidopsis with Bacillus megateriumBM2 fermentation broth.The experiment showed that the fermentation broth had a dilution ratio of 500,and its rooting effect on Arabidopsis was the best,and the root length increased by 67.4%.When the dilution ratio was 50,the growth promoting effect of Arabidopsis was not obvious.The root length of Arabidopsis under different dilution times was significantly different from that of the arabidopsis.Bacillus megaterium BM2 fermented liquid treated with different dilution times played a role in promoting the growth of cucumber seedlings.Along with the increase of Dilution Times on cucumber seedling growth effect is more obvious in the fermentation broth diluted 500 times treatment,compared with the control group had significant difference,the plant height increased 25%,cucumber seedling fresh weight compared with the control group increased 37% and 1000 times diluted fermentation treatment,compared to significant difference with the control group,the plant height increased 51%,cucumber seedling root length was 21% higher than the control group,the cucumber seedling fresh weight increased 39% than the control group.There was significant difference between the two groups(P <0.05).The addition of fermented liquid could promote the growth of root length of cucumber seedlings.