First, to briefly summarize the characteristics of E. coli that we designed, it has the property of accumulating more phosphorus and maximizes its ability by the addition of an inducer. In other words, E. coli is implemented in the place where the phosphorus needs to be recovered, E. coli can grow, and phosphorus is concentrated. Looking at the material flow diagram of phosphorus (Fig. 1), it is difficult to recover phosphorus released into rivers because it diffuses, but it is possible to recover it from domestic and factory wastewater before it flows out into the environment.
(Fig. 1) the material flow diagram of phosphorus
Therefore, it is conceivable that the introduction destinations are the Waterworks Bureau, which currently collects phosphorus using microorganisms by the activated sludge method, and the wastewater treatment plants of food factories and chemical factories where water containing a high concentration of phosphorus is discharged. If the E. coli we produce is introduced along with the microorganisms in this activated sludge, phosphorus will be removed from the wastewater more efficiently.
In order to introduce it into the real world, it is necessary to add the produced E. coli to activated sludge. Microorganisms in activated sludge can grow by utilizing the nutrients in activated sludge, so they grow naturally without adding nutrients. In case there is a shortage of E. coli, we are also considering selling additional E. coli to supply it.
As a safety issue, genetically modified E. coli must not be released into nature. Currently treated water is disinfected by adding sodium hypochlorite or by exposing it to UV light and then draining it. Disinfection brings it to a certain level, so that only a few individuals can exist in 1 cm³. In fact, it is necessary to prevent the extraction of even one genetically modified organism, so additional measures are required. We believe that biological containment by amino acid requirements is practical.
The problem with removing phosphorus itself is that enough phosphorus has already been removed in Japan today, and there is not much need to actively remove phosphorus anymore. Nowadays, there are rather oligotrophic seas, which have an impact on fishery resources that require phosphorus, such as seaweed. Of course, there are still some places where the occurrence of water bloom is a problem in closed waters such as Lake Biwa, Kasumigaura and dams located downstream of rivers, but they remain local. We should consider not only Japan but also the other countries where the damage of water bloom continues.
In addition to removing phosphorus to prevent deterioration of environmental conditions, the recovered phosphorus should be reused. There are three reasons.
The first reason is that phosphorus is a depleted resource. About 60% of phosphate ore is predicted to be depleted by 2070. Phosphorus is a life-sustaining element and is often used in food production. In other words, if it disappears, it may not be possible to cover the diet of humankind on Earth. Unlike carbon, when phosphorus spills into the sea, the only natural pathway to land is through seabird droppings or fish runs, so there is little phosphorus circulation in the short term. Therefore, I think phosphorus needs to be manually recovered before it is released into the sea. In addition, phosphorus is a strategic material and may not be supplied in a stable manner depending on the social situation. Especially in Japan, where phosphate ore is not available, stopping phosphorus exports will have a serious impact on food production.
The second reason is that E. coli that has recovered phosphorus contains phosphorus at a concentration higher than that of phosphate rock. The high-quality phosphate ore currently mined contains 13% phosphorus .However, E. coli is known to be able to accumulate more phosphorus. The higher the concentration of phosphorus, the easier it is to concentrate phosphorus, which may make it a suitable material to produce phosphorus products.
Thirdly, the activated sludge produced by the activated sludge method can be reused for cement, but phosphorus contained in the activated sludge adversely affects the production of cement and high phosphorus containing cement is not actively utilized. This is also the reason we currently need a way to extract and reuse only phosphorus.
The main sources of phosphorus reuse are fertilizer and yellow phosphorus production. Phosphorus is consumed in very large amounts in the world, most of which is used as fertilizer. If it is reused as fertilizer, the problem is the price. Phosphate ore, which is the source of phosphorus fertilizer, is currently mined at a low price, so the fertilizer itself is also cheap. Therefore, it is required to recover phosphorus as cheaply as possible.
If only the phosphorus content could be isolated and recovered, it might make a good source of yellow phosphorus. The MAP method, which is a method of reusing phosphorus, needs an expensive magnesium, and the price of fertilizer produced is equal to or higher than that of fertilizer produced from phosphate rock. In addition, running costs have become a problem due to too much maintenance costs. However, since we know that polyphosphate in activated sludge can be isolated by heating and can be converted to artificial phosphorus ore with relatively small amounts of calcium , our E. coli bacteria could be useful if a new phosphorus reuse pathway is developed.
1. Matsubae, K. et al. (2009). A Material Flow Analysis of Phosphorus in Japan. Journal of Industrial Ecology. 13(5). 687-705.
2. Kuroda, A. et al. (2005). Development of Technologies to Save Phosphorus Resources in Response to Phosphate Crisis. Journal of Environmental Biotechnology. 4(2). 87-94
3. Ohtake, H. et al. (2000). Strain Improvement of Phosphate- Accumulating Bacteria and Heat Extraction of Polyphosphate from Activated Sludge. Journal of the Brewing Society of Japan.95(1). 23-28