| Formaldehyde is one of the major contaminants in the room and is hazardous to health because of its large toxicity and sustained volatility.Formaldehyde in the environment exists in a variety of forms:such as in the form of liquid present in the water;in the form of solid compounds exist in clothing,furniture,soil matrix;in the form of gas in the atmosphere and indoor air.In recent years,for the pollution control of formaldehyde,many researchers at home and abroad developed a variety of technologies.In a large number of indoor formaldehyde pollution control technology,the use of plant removal of formaldehyde in the environment pollution,with a simple,economical and environmentally friendly features.Recent studies have shown that bioreactors with plant roots and soil matrices can effectively remove aerobic formaldehyde in the indoor environment.In this study,Dr.Tan Hao's paper has elucidated the metabolic mechanism of formaldehyde metabolism in black soybean SB and found that glyoxylic acid pathway plays an important role in the metabolism of SB formaldehyde.In this study,ICL and MS gene expression levels and enzyme activities in SB roots were changed by activating agents and inhibitors of ICL(citrate lyase)and MS(malate synthase),respectively.The ICL and MS SB roots were used to metabolize formaldehyde.At the same time,the optimal combination condition of formaldehyde was optimized by using the reaction surface.Then,the suspension bioreactor was constructed with SB root,and the performance of the reactor in the removal of indoor formaldehyde pollution was analyzed.The expression profiles of ICL and MS genes in SB soybean roots treated with different concentrations of formaldehyde were analyzed by RT-PCR.The results showed that ICL and MS genes were treated with low concentration of formaldehyde(2mM)for 4,12 and 24 hours,high concentration(4,6mM)The results of qRT-PCR analysis showed that the expression of ICL gene in the treatment of 2mM formalin for 0.5h,2h,4h,12h and 24h respectively reached the control level of 6.2,1.97,6.4,2 times,respectively,in 4,6mM formaldehyde The expression of MS gene was increased to 5.31.9 times after treatment for 2 hours,and the expression of MS gene was 9.8,1.7,1.2 and 3.4 times higher than that of control group at 2 h,4 h,12 h and 24 h after 2 mM formalin treatment.1.6 times,these data confirm that ICL,MS expression was induced by formaldehyde stress.The results showed that the addition of 10 mM glucose,5 mM mannose.10 mM sucrose and ICL were observed by the combination of ICL and MS(glucose,mannose,sucrose)and activator(methanol,MgCl2,IAA)respectively.MS expression and enzyme activity were significantly decreased.The expression of ICL and MS gene was significantly increased when ICCI and MSC1 were treated with 4mM methanol and 1mM MgCl2.The ICL reached 16.5 times and 7 times of that of control,6.4 times of MS and 5.6 times,respectively.The activity of ICL and MS was also improved greatly.13C-NMR analysis showed that the addition of mannose or glucose to H13CHO treated with SB roots resulted in a reduction in the production of metabolites Malate.Cit.Glucose produced by the cyclic circulation of glvoxylic acid.The addition of methanol to H13CHO resulted in a significant increase in the yield of SB roots.Malate.Cit and Glucose.which confirmed the important role of gluoxylic acid cycling in the metabolism of formaldehyde in SB roots.Using the Central Composite Design to design the mathematical model,the optimal condition of the formaldehyde absorption of the SB plant roots was obtained by using the response surface optimization method.The regression equation was obtained by fitting the regression factors of the test factors to the response value:Y = 23.14-17.35A-6.84B + 3.75C + 3.55AB-0.90AC-3.86BC + 11.63A2 + 6.00B2 + 1.56C2.the model predicts the concentration of formaldehyde,the volume of treated solution and the fresh weight of soybean are 0.099mM,0.273L And 38.74 g.the absorption efficiency of formaldehyde was the highest,the predicted value was 73.74%,and the real value verified by the experiment was 71.40%?The results show that the model is well fitted.The results showed that there was a small amount(0.5%)of free formaldehyde in the roots of 1h.2h and 4h.and no residual was found in the roots after 24 to 48 hours of treatment.formaldehyde.Free formaldehyde in stems and leaves reached the highest level(1?3%)at 4 h.The results showed that the formaldehyde absorbed through the roots was transferred to the stem leaves and then entered into the air.but the transfer of formaldehyde was not affected by the total amount of formaldehyde in the air around the stem and leaf during the period of 1?12 h.The contribution of formaldehyde removal is small(less than?4%).The results showed that the transpiration rate of SB was the highest at 2 h.and the concentration of formaldehyde in air was also reached the highest level.When the treatment time lasted for 12 h,the transpiration rate decreased significantly,and the evaporation rate of formaldehyde in the air decreased rapidly.These results indicated that the process of formaldehyde transfer to the air in SB soybean plants was dependent on transpiration,while formaldehyde stress significantly inhibited SB Of transpiration.The effects of the initial concentration of formaldehyde on the removal efficiency of formaldehyde in the reactor were investigated.The results showed that the removal rate of formaldehyde in the reactor was 284 g fresh weight(60%?70%),After fixing these two conditions,the reactor was placed in a solution containing formaldehyde with different initial concentrations,(1.2 mg/m3)and high concentration(7.4 mg),respectively.The results showed that the suspension treatment system was better than 60%in the initial concentration of 3 mg/m3 formaldehyde,/M3)formaldehyde pollution of the environment purification effect is less than 50%.The TVOC purification effect is higher for higher concentrations(7 mg/m3,9.6 mg/m3)in the environment,but for higher concentrations(5.6 mg/m3)of TVOC,the removal efficiency of the reactor is higher. |
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