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.