Study On Removal Of Cd In Water And Sediment By Filamentous Fungi

Heavy metals and their compounds are widely used in industrial and agricultural production and life,without strict treatment and directly discharged into the environment,not only harmful to the normal operation of the industry and agriculture,but through a series of food chain transmission process,and ultimately endanger human health.Heavy metals accumulate mainly in water and soil,while water and soil are closely related to human production and life.Therefore,it is very important to reduce or eliminate the toxic effects of heavy metals effectively.Filamentous fungi are widely used in the environment of a class of microorganisms,and have a strong adsorption removal effect for heavy metals,thus the use of filamentous fungi as the representative of the microbial repair of heavy metals in the environment has a very broad prospect for development.In this paper,two common filamentous fungi,Aspergillus fumigatus and Aspergillus niger.To understand the effect of Aspergillus fumigatus on the removal of Cd in water and soil,the removal of Cd from aqueous solution and the removal of heavy metal Cd in soil by semi solid culture were simulated.Then,to further explored the removal effect of filamentous fungi on Cd in the semi-solid culture conditions,the two strains were used for the restoration of the sediment in Xiangjiang River.The results of shaking flask culture showed that Aspergillus fumigatus could remove about 50%of Cd in the culture medium,and the removal effect was the best when the concentration of Cd was about 50 mg/L,which was up to 55.5%.In the experiment,the optimum conditions for removing Cd in the system were temperature 30?,pH 5,the addition of liquid was about 120 mL,the rotational speed was 100 r/min,and the inoculation amount was 0.4mL(1.0×107 CFU/mL).GSH plays an important role in the removal of Cd under the condition of active growth of Aspergillus fumigatus.The increase of GSH content is positively correlated with the removal of Cd.GSH detoxification is caused by GPx and GR oxidation of intracellular excess oxidizing substances or the combination of Cd and chelate compounds into the body.The experimental results showed that with the increase of Cd concentration,the absolute weight of Cd was increased,but the removal rate decreased gradually with the increase of Cd concentration.When the concentration of Cd was 10 mg/kg,the removal rate of Cd by Aspergillus fumigatus was up to 31%.In course of cultivation,the biomass dry weight decreased with the increase of incubation time and Cd concentration,and the maximum decrease was 64%,and the optimum pH was 5.6-6.0.The morphology of Cd in the culture system was mainly weak acid soluble and reducible,and the oxidation state remained unchanged before and after culture.The experimental results of filamentous fungi removal of Cd from the Xiangjiang sediment showed that the maximum amount of Cd in Aspergillus fumigatus was 75%higher than that of Aspergillus niger.;by comparing the two kinds of fungal extracellular and intracellular accumulation of Cd adsorption was also found that the content of Cd in the sediment removal of Aspergillus fumigatus was significantly higher than in Aspergillus niger.In the training process of biomass dry weight decreased with the time and concentration of Cd in culture,and the largest decline of 64%,the optimal pH is 4.8-6.0,GSH content decreased gradually,the maximum decrease of 7.539 ?mol/g.