Plastics, as macromolecular chain polymers, have a heavy burden on the environment due to their difficult to degrade properties. Scientists have recently proposed a biodegradation method that uses a newly discovered enzyme to break down plastic bottles to complete the recycling of plastic waste.
This enzyme comes from a bacterium found in 2016. As a decomposer in nature, microorganisms often face artificially polymerized plastic macromolecules. The idea of the Odagi Gengping team at the Kyoto Institute of Technology in Japan is that in densely populated areas, it is difficult for microbes to obtain stable carbon sources, and the ability to degrade plastics may be hunger.
They collected a large number of contaminant samples from a plastic bottle collection point, mixed with polyethylene terephthalate (ie PET, the main component of plastic bottles, accounting for 1/5 of global plastics production), and screened out PET as a food. "The bacteria Ideonella sakaiensis.
In the paper of the year, the team proposed the mechanism of the bacteria degrading plastics: by decomposing the PET polymer into monomers by the PET degrading enzyme, and then transporting the monomers into the cells and decomposing into ethylene glycol and terephthalic acid. Both products can be recycled as chemical raw materials. The study found that the plastic film used in the complete degradation experiment took only a few weeks.
The process by which bacteria degrade the film. Image courtesy of Feeding on plastic,Science 2016
Two years later, an international team led by John McGeehan of the University of Portsmouth in the UK used diamond X-ray analysis to elucidate the high-definition 3D structure of the enzyme and attempted to improve its degradation efficiency through modification. The paper was published this week in the Proceedings of the National Academy of Sciences.
The structure of the PET degrading enzyme was obtained by analyzing the brightness of 10 billion times of the daylight diamond source. The researchers found it to be similar to some of the bacteria used to degrade the stratum corneum of plants. The team attempted to mutate the active site of the PET-degrading enzyme to obtain activity characteristics similar to cutinase. The intention was to verify whether the PET enzyme lost the ability to degrade the plastic, but unexpectedly increased the efficiency of the enzyme by 20%. .
The modified enzymes begin to degrade plastic bottles in just a few days, much faster than the hundreds of years required in the natural environment. The researchers said that the efficiency of the enzyme can be further improved and can be used for other plastic materials. In a similar example, industrial enzymes, which are widely used in the production of washing powders and bioenergy, can increase the catalytic efficiency by a factor of 1000 over several years of improvement.
An improved method being explored is to transplant the enzyme into a bacteria that is resistant to high temperatures. At 70 ° C, PET becomes hard and viscous, and the decomposition efficiency is improved.
According to Professor McGeehan's idea, if this enzyme can be used to reduce plastic polymers into monomers, the recovery rate of plastics will be greatly improved, while reducing the demand for raw oil.
The biodegradation of other types of plastics has also made some progress. For example, the Xu Jianchu team of the Kunming Institute of Botany of the Chinese Academy of Sciences found the Aspergillus spp. which can degrade the polyurethane (PU). The Yang Jun team of Beijing University of Aeronautics and Astronautics also discovered the degradation poly Insects such as ethylene.
The biological enzyme is non-toxic, efficient and easy to mass produce. It is an ideal tool for decomposing plastic waste, provided that it has stood out from countless screening and optimization. New research shows that optimization of PET-degrading enzymes is feasible, and new methods for dealing with white pollution are taking shape.
Can plastic bottles be reused and what are the hazards? Do you know?
Can the wine be packed in plastic bottles? Will plastic products be corroded? We have seen so many plastic bottles on our side of life, what else can we do besides loading things? What is the plastic bottle made of? How long can I save? Is there any poison, etc? What is the difference between it and plastic bags? What is the difference between national food safety plastics and private ones? Let's take a look at it. Is it really safe to put the Moutai in a mineral water bottle? Is there any other problem?
Since wine is a kind of acidic solution, long-term storage and plastic bottles may cause plastic bottles to be slowly dissolved or acid-etched by alcohol, especially high-density alcohol is more likely to appear, so do not take long Stored. Moreover, the heat resistance of these plastic bottles is limited. If the temperature is high or the retention time is too long, the loaded food will release harmful substances.
Will pickled pickles in plastic bottles be corroded? Which foods can't be placed in plastic bottles? The ingredients of pickled vegetables are not enough to corrode plastic bottles, but harmful substances in plastic bottles can penetrate into pickles and affect health. Many families like to store all kinds of seasoned beans in plastic bottles for convenience and economy. Nowadays, many young people still do this, and don't feel wrong.
Experts: It is best to use glassware. Most of the bottles are made of PET. This is a kind of polymer material. It is generally non-toxic and tasteless at low temperature. It is safe for people to drink. In this regard, Jiang Min, the head of the Jinling Middle School Chemistry Group, believes that since beverage bottles can hold beverages such as cola and can be safely tested after inspection, the problem of the beverage bottles themselves should not be very large. The second use of plastic bottles or repeated use of plastic bottles is harmful to the human body. It depends on the amount of hazardous additives in such plastic bottles and the different sensitivities of individuals. After all, a substance can cause cancer, but not every contact. People will get cancer. And no matter what, you have to say a quantity problem, such as normal breathing oxygen, to maintain the body function is no problem, but excessive oxygen can easily lead to oxygen poisoning.
Plastic bottles are not suitable for repeated use. If a plastic bottle is used for a long time, it will cause decomposition of the plastic. Then, the toxic substances in the plastic will enter the human body with the seasoning, which will threaten human health. Therefore, in order to live a happy life, you must not use plastic bottles repeatedly to load food. The second use of plastic bottles is harmful. In the concept of many old people, the things that can be used are not thrown casually, it is too wasteful. Many old people use plastic bottles to wash detergent, laundry detergent or some kitchen spices, such as soy sauce, vinegar, etc., 1.25 liters of Sprite bottle, 4 liters of Nongfu Spring plastic bucket filled with rice or beans, many young people today People still do this, don't feel wrong.
Recently, however, Weibo news has spread that it is not necessary to use toxic solvents twice to endanger health; aging of plastic bottles will also release ethylene monomer, causing dizziness, nausea, memory loss, and anemia; bacteria can easily multiply in bottles. Most citizens recycle plastic bottles. The ingredients of pickled vegetables are not enough to corrode plastic bottles, but harmful substances in plastic bottles can penetrate into pickles and affect health. For convenience and economy, many families like to store various seasonings in plastic bottles, which is considered to be not harmful to human health. However, experts have found that plastic bottles are not conducive to human health. What are the hazards of putting food in plastic bottles? The hazards of repeated use of plastic bottles are described below.
Feel free to walk into a snack bar, you can see the plastic bottles with oil and salt vinegar, and some small peppers modified with plastic bottles, it looks very small and exquisite, there are experts: it is best to use glassware Drinking, this is a kind of polymer material, generally non-toxic and tasteless at low temperature, and the beverage is safe for the human body. Repeatedly, it is harmful to the human body. It depends on the amount of harmful additives in such plastic bottles and the sensitivity of individuals. After all, a substance can cause cancer, but not every person who comes into contact will get cancer. And no matter what, you have to say a quantity problem, such as normal breathing oxygen, to maintain the body function is no problem, but excessive oxygen can easily lead to oxygen poisoning. Many shop owners said, "Why are the plastic bottles, we are all washed and reused, and we have not used them to put on hot things. It should be safe to use."
1. Disposable paper cups or hidden potential carcinogens Disposable paper cups just look hygienic and convenient. In fact, the product qualification rate cannot be judged, whether it is clean and hygienic, and it cannot be recognized by the naked eye. From an environmental point of view, disposable cups should be used as little as possible. Some paper cup manufacturers add a large amount of fluorescent whitening agent to make the cup look whiter. But this kind of fluorescent substance can make the cells mutate, and once it enters the human body, it becomes a potential carcinogenic factor. Secondly, those unqualified paper cups are generally soft, easy to deform after pouring into water, and some paper cups are poorly sealed. The bottom of the cup is easy to seep, which makes it easy for hot water to burn your hands. What's more, when you gently touch the inside of the paper cup by hand, you can feel the fine powder on the surface, and the touch of the finger will turn white. This is a typical inferior paper cup.
2, plastic cups are the most vulnerable to dirt and dirt plastic cups should also be an unwelcome one. Because plastics are often added with plasticizers, which contain some toxic chemicals, when using hot water or boiling water in plastic cups, toxic chemicals are easily diluted into water, and the internal microstructure of plastics has many pores. It hides dirt, and it is easy to kill bacteria when it is not cleaned. Therefore, when purchasing plastic cups, be sure to choose a cup made of food grade plastic that meets national standards. 3, multicolored water cups are easy to cause heavy metal poisoning.
Colorful cups are very attractive, but it's best not to use them. Because there are huge hidden dangers in those bright pigments, especially when the inner wall is coated with glaze, when the cup is filled with boiling water or acid or alkaline beverage, the toxic heavy metal elements such as lead in these pigments are easily dissolved in the liquid. People who drink liquids with chemicals can cause harm to the human body. 4, metal material cups of coffee will dissolve metal cups, such as stainless steel, the price is more expensive than ceramic cups. The metal element contained in the enamel cup composition is generally stable under normal conditions, but it may be dissolved in an acidic environment, and it is not safe to drink acidic drinks such as coffee or orange juice. The safest drinking cup
Ceramic cups painted without color glaze are preferred to ceramic cups without color glaze, especially for the inner wall. Not only material safety, high temperature resistance, but also relatively good insulation effect, drinking hot water or drinking tea is a good choice. Therefore, in order to be healthy, drink water to choose the right cup, beware of the water cup causing disease hazards.