Screening Of White Rot Fungi For Dye Decolorization And The Studyon Its Decolorization

Dye wastewater is a kind of environmental pollutants which has complex structure,high chroma,high organic content,poor biodegradability and potential toxicity.Exploring the methods of efficient treatment of dye wastewater has become an active research area.The white rot fungi has come to focus on treating dye wastewater because of its special degradation mechanism.Isolating and screening efficient white rot fungi has great significance.At the same time,when the white rot fungi was cultured in non-sterile environment,how to avoid contamination and resolve the problem that the enzyme activity was destructed by mechanical shear stress which led to ineffective decolorization has been the bottleneck of practical application of white rot fungi.In this paper,we isolated and screened a white rot fungi which has high decolorizing efficiency from the field.And I made a study on its enzyme-production characteristics,the process parameters of decolorization,and decolorization of dyes in non-sterile environment.Through the study,the following conclusions were made:(1)We isolated and screened a white rot fungi named G2 which had high decolorizing efficiency from the rotten wood in the forest.And we determined the growth and enzyme production curves.The results showed that,G2 produced Lac and MnP majorly.When G2 was cultured in static and nitrogen-limited culture,the enzyme activity of Lac and MnP reached peak at the seventh day and the nineth day.The maximum activity was 190.1U/L and 37.8 U/L.(2)Selecting congo red,malachite green and crystal violet as the dyes of decolorization,we optimized the the process parameters of decolorization.The results showed that,the optimal liquid culture medium was:10g/L dextrin,0.88g/L ammonium tartrate,0.2g/L Mn2+,0.1g/L Cu2+,0.5g/L surfactant Tween 80 as main component.And the optimal fermentation conditions were:culture temperature 30℃,shaking speed 120 r/min,pH 4.5.Under these conditions,after 6d,added dyes.The final concentration of congo red,malachite green and crystal violet was 50mg/L,50 mg/L and 35mg/L.After 36h,the decolorization rate of congo red,malachite green and crystal violet were 95.7%,98.5%and 90.2%,increased by 21.1,18.4 and 24.8 percentage points compared with the decolorization rate 74.6%,80.1%and 65.4%under not-optimal conditions.(3)Through nutritional regulation,we made a study on the decolorization of G2 in non-sterile environment.The results showed that,there are five kinds of carbon and nitrogen concentration,respectively,1(dextrin 10g/L,ammonium tartrate 0.88g/L),2(dextrin lOg/L,ammonium tartrate 0.22g/L),3(dextrin lOg/L,ammonium tartrate 2.2g/L),4(dextrin 2g/L,ammonium tartrate 0.22g/L),5(dextrin 2g/L,ammonium tartrate 2.2g/L).The final concentration of congo red,malachite green and crystal violet was 100mg/L,100mg/L and 50mg/L.When culture and decolorization were both in sterile environment,afer 48h,the decolorization rates of dyes using G2 were:l>2>4>3>5.And the decolorization rates of three dyes were:malachite green>congo red>crystal violet.When culture and decolorization were both in non-sterile environment,afer 48h,the decolorization rates of dyes using G2 were:2>4>1>5>3.And the decolorization rates of three dyes were:malachite green>congo red>crystal violet.The experimental results showed that when culture and decolorization were both in non-sterile environment,the culture system had stronger ability to inhibite bacteria in N-limited culture(2 and 4).When the concentration of dextrin was 10g/L,the concentration of ammonium tartrate was 0.22g/L,the decolorization is best.After 48h,the decolorization rates of congo red,malachite green and crystal violet were 68.4%,76.6%and 63.1%.(4)Experiments also compared the decolorization of G2 between free culture,immobilized cells by Ca-alginate and immobilized cells by loofah.The final concentration of congo red,malachite green and crystal violet was 100mg/L,100mg/L and 50mg/L.In free culture,after 48hs the decolorization rates of congo red,malachite green and crystal violet were 70.20%,79.1%and 64.7%.Immobilized cells by Ca-alginate,the decolorization rates of congo red,malachite green and crystal violet were 80.8%,88.6%and 76.8%,increased by 10.6,9.5 and 12.1 percentage points relative to the free culture.Immobilized cells by loofah,the decolorization rates of congo red,malachite green and crystal violet were 88.8%,95.3%and 84.2%,increased by 18.6,16.2 and 19.5 percentage points relative to the free culture.