Team:FAFU-CHINA/HP/Gold Integrated
Interview with Prof. Zhou Shungui
After primary brainstorm, we still had numerous queries related to the details and principles of our project because enviromental engineering this suject is totally brand new field to all of our team members, that is to say, it is not only a project but also a huge chanllenge for us during the coming year. In this regard, we had a interview with Prof. Zhou Shungui, who is an expert in environmental engineering and environmental bioelectrochemistry for almost 10 years.
After hearing our brife introduction, He pointed out that in spite of great potential, phosphate-solubilizing bacteria and their relations with host plant under heavy metal contaminated soil are very less understood and require to be explored further. Synthetic biology as a latest biotechnolugical tool could be done to accelerate synergistic action of PSB in enchancing the growth of plant and their mechnisms. Although the route of cellular entry remains unknow for several toxic metals and substantial gaps in our knowledge, it is clear that the uptake of non-essential metals often involves metal binding proteins and regulators that are dedicated to acquisition of essential inorganic and organic ions.
Thanks to Prof. Zhou’s advice, we found out some metal binding proteins in the parts pool and started to improve our chassis.
Communication with Entrepreneur
iGEM group：According to your years of field investigation and research, from what specific origins the heavy metal pollution arises? And by what means the heavy metal pollutes soil?
President Shi: At present, the metals that caused serious pollution include Cd, Pb and Hg. The enrichment of Cd in soil makes some crops, especially rice, excessive in the amount of heavy metal, which is actually what we call “Cd-polluted-rice”. The phenomenon is caused by the utilization of a kind of quick acting fertilizer, urea, in great amount, which can increase rice yield. When the massive loss of nutrient occurs in soil, a great amount of silicon-calcium-magnesium fertilizer will be used as soil conditioner to alleviate the trouble. But the problem is that the raw materials of such fertilizer are the by-products of cadmium and steel chippings in steel production. To lower costs, the steel chippings are used in the fertilizer before they are processed consciously with pertinent technologies, and thereby becoming one of the largest pollution sources of the poisonous heavy metal, cadmium.
And the main source of mercury is the improper disposal of municipal waste. The best method to dispose municipal waste currently is incineration. But landfill remains to the major method to dispose the largest proportion of municipal waste, and the steps of disposal do not include filtration and classification, for which the pollution sources like waste batteries that are rich in mercury enter groundwater or are used in cheap organic fertilizers. The other source comes from the disposal of municipal sludge. In effect, a sharp contradiction has arisen between the increasing volume of sludge in China and its serious weakness in disposal, backwardness in disposal approach. A great deal of sludge is transported out, dumped or filed up at random, causing the “sludge-surrounding” phenomenon in many cities. And the waste containing mercury from daily life can cause secondary pollution by entering sewage system. Guangzhou Daily reported in 2009 that a cleaning company piled sludge in a forest farm locating between TangShalin village and ZhangMuTou forest farm, and then the heavy metal in the sludge infiltrated into a fishpond, which killed 15,000 kilograms of living fish.
The pollution source of lead generally comes from the waste water and chippings leaked by paper mills in the upper reaches of urban water system. The waste that is excessive in lead is used in the production of cheap organic fertilizers, which will enter soil system once again.
In addition to the pollution sources above, the raw material used in the production of cheap inorganic salt, magnesium sulfate, is the waste sulfuric acid from galvanizing plants; glyphosate acid in the waste liquid from the production of herbicide, glyphosate, is recycled before being disposed properly, which constitutes another important pollution source.
Fig. 1 During this visit to Zhangzhou, we exchanged opinions and discussed on the project’s background, thinking pattern and some problems in practice with the president Shi Jinsheng in Fujian Kunsheng Agriculture.
iGEM group：Can you make some comments and suggestions after hearing our thinking pattern of the project?
President Shi: As a matter of fact, we tend to apply micro-molecular humid acid or organic fertilizers of amino acid in practical utilization to fix or mobilize the necessary soil elements for plant’s growth. But the problem is: helpful and harmful elements will be fixed or mobilized simultaneously in the process, and thereby making it impossible to carry out a precise and peculiar selective fixation/mobilization. In your project, the heavy metal pollution is handled by the joint application of peculiar metal transporter protein and hyperaccumulator, which is pretty good.
iGEM group：If our project needs to be applied in practice, what will be the specific operation processes? And of what aspects shall we be conscious?
President Shi: Generally speaking, phosphate solubilizing bacteria will be subject to a series of courses to rejuvenate and ferment, and then be colonized in the plant root as the added substance of organic fertilizers. That can control the reproduction of harmful bacteria in soil effectively on one hand and disintegrate phosphorus and potassium on the other hand. In addition to organic fertilizers, something like fermentation liquor of cane sugar, fermentation liquor of alginic salts, etc, is also a good carrier. It is to guarantee an adequate carbon source and nitrogen source that matters. Talking about the aspect you should very care about is safety. Currently, it is unclear whether the unmonitored release of every genetically engineered microbe(GEM) into the enviroment is absolutely harmful or absolutely safe, especially your project, which actually is referring to GMO that has been controversial for almost 20 years in China, even world. Decades of scientific research and changes in government polices may be needed to determine and define the danger or safety of every type of GEM, as current information is sparse.
Field Research
Background
The pollution of heavy metals in agricultural soils in our country is mainly due to the increase of the area and the degree of increase. The heavy metal pollution in the soil is mainly from the sewage and solid waste. We have learned from the research in Zhangzhou City, Fujian Province that the chemical and pesticides are the most important possible pollution sources.In addition to the paper mill waste discharge, improper waste disposal, random accumulation is also a very likely source of pollution.Therefore, we purchase the commonly used fertilizer from farmers in Fuzhou City, Fujian Province, while the national use of the popular use of soil regulators to detect the chemical fertilizers for soil heavy metal pollution.Subsequently, we also visited the manufacture of chemical fertilizer manufacturers and a number of local paper mills and found that more than 10 years ago there, and a number of paper mills due to serious pollution has long been removed.
Reagents
Nitric acid,perchloric acid (excellent grade),Fe, Mn, Cu, Pb, Zn, Cd standard stock solution, the experimental water is deionized water, the utensils are washed with 10% dilute nitric acid and then soaked with deionized water overnight.
Sample source
Organic fertilizer(Shandong Chenlan Biological Technology Co., Ltd.),
compound fertilizer (Shandong Chen Lan Biological Technology Co., Ltd.),
calcium magnesium phosphate, Fujian Province in the Norwegian fertilizer Limited
Compound fertilizer，Shandong Chenlan Biological Technology Co., Lt
Soil conditioner， Fujian Province in the Norwegian fertilizer Limited
High tower compound fertilizer， Fujian Fu Nong Agricultural Resources Group Co.,
Ltd complex fertilizer，Greens Fertilizer Yantai Co., Ltd.
Calcium - containing nitrogen fertilizer，Fujian Fu Nong Agricultural Resources Group Co., Ltd
NPK compound fertilizer， Shandong Chenlan Biological Technology Co., Ltd
Calcium magnesium phosphate soil conditioner，Hebei Yang is the yuan Chemical Co., Ltd
calcium magnesium phosphate
Sample processing
The determination of the total amount of Cd、Cr、Pb、Fe and Zn was digested with HNO3-HClO4, The sample was pulverized with a pulverizer.
A.sample of 1.00 g of each sample was weighed into a 100 ml Erlenmeyer flask
B. Add 6 ml of mixed acid (HNO3: HClO4 = 5: 1) and mix well, Placed in the hot plate on the low temperature to produce a large number of white smoke,The solution was yellow and then cooled,Add a small amount of water,Boil to remove residual nitric acid to produce white smoke.
C. repeat the treatment twice, let them let the cold,Into the 250ml volumetric flask,The residual liquid in the flask is washed and set to a graduated line.After dilution, the solution contains floc, filter, take clear solution.
Determination of heavy metal content of fertilizer with AAS. Measurement results in the table below：
Different countries have different standards for heavy metals in fertilizers.
Our country's latest fertilizer products harmless indicators of national standards and industry standards in the table below:
From this table we can see that we take the fertilizer samples in Fuzhou are in line with national standards and industry standards.My teammates and I all feel lucky for this result because living on such a safer land.However, European countries from the European Union on the fertilizer heavy metal limit the standard table tells us things are not simple.
Among them, Denmark, Germany, and Italy have very strict limits on environmental hormones Pb, Cr, Hg, and they are still looking for a lower standard value.Moreover, many countries use two or more multilevel system, more precise and more stringent control fertilizer in the output of heavy metals.Although the heavy metals in the fertilizer had a systematic investigation in the early nineties of the 20th century in China , the system is still more broad, need to be further adjusted to ensure that the ecological environment, soil and crop safety.In fact, if we think about it, it is not difficult to find that when tens of thousands of fertilizer is cast in the soil, it is inevitable that a large number of heavy metals are carried, no matter how low standards.This is why in the case of fertilizer to achieve the standard of China is still a large number of heavy metal pollution of the soil, widely distributed and difficult to manage, to the environment caused irreparable damage.It is for the above considerations, this year our team screening of soil in the giant bacillus. After the transformation, we put it in the form of biological agents added to the soil, not only can effectively avoid the improper use of fertilizer caused by heavy metal pollution, but also to promote the growth of plants, thereby increasing crop yield. Won in one fell swoop!
