Engineering Microbulbifer hydrolyticus for plastic degradation and value-added products
Plastics are widely used in industry and households because of their low-weight, durability and low-production cost. Nowadays, the consumption of plastics has risen sharply. However, lack of effective waste plastics management poses a major threat to the environment. For the past few years, new technology about biodegradation of plastics has been a hot spot. Polyethylene (PE) and polystyrene (PS) are the most important mass-produced plastics, which are difficult to be degraded by the microorganism. Recently, we observed a strain Microbulbifer hydrolyticus , which has the ability to degrade PE and PS. In this study, we would try to investigate the mechanism of PE biodegradation, and find the key enzymes. Meanwhile, based on the genome sequencing and synthetic biology, we aim to construct an artificial metabolic pathway, engineering this strain to enhance the ability to plastics biodegrading. Furthermore, the strain could utilize plastics to synthetic value-added products, such as PHA, etc.
Due to the great properties of plastic products, such as chemical stability, excellent clarity, toughness, etc , it has an irreplaceable position in people’s daily life. However, it also brings incalculable plastic waste while bringing convenience to our life. Generally, the degradation of plastics needs hundreds of years and some of them even cannot be degraded, and the problem which results from plastics is imminent. The mainstream method is still to treat plastics by landfill or incineration which cannot resolve the problem. The whole world is concerned about how to deal with those waste plastics, what’s more the PE materials become the focus of our attention. With the help of synthetic biology, our iGEM team tend to design and optimize a way to degrade PE by microorganisms.
Environmental issues cannot be ignored, so many topics on plastic degradation are being studied. In our surroundings, we could see many plastic garbage, and some abandoned plastic garbage seems to have been degraded by nature.In fact a large part of which becomes micro-plastics in ocean and land,then entering the animal’s body through the food chain even our human beings. Because those tiny plastic is really difficult to be collected，so there is currently no good way to deal with these micro-plastic whether using chemical or physical methods,and it has become an urgent part of the problem of plastic pollution. Besides,though many plastics can be degraded and recycled, but it is estimated that roughly 50% plastic will be buried in the land rather deal with them. So it has a large space to improve them in this area. Such as PE can also be degraded into CO2 but its hard to be reused.So recycle is indeed a big problem. Based on the above two issues:collect and recycle, we try to use microbes to find more effective methods. So we are trying to do something on PE in order to contribute a little to our environment, which have profound realistic meaning.
We find that a Marine strain has a certain effect on the degradation of polyolefin. Through whole-gene sequencing, transcriptome analysis and other biological technologies, we know that this strain can produce a large number of oxidase and the main biological reaction is the metabolism of carbon compounds. We find a key oxidase gene in the genome of Marine strain that can degrade PE directly into short carbon chains, rather than by introducing active functional groups. We extract the gene from the genome of the Marine bacteria and use genetic engineering technology to introduce it into E.coli BL21 to construct an engineering strain. Finally, the polymer model (long chain alkane) is used to verify that the engineering strain could improve the degradation efficiency of the polymer, which prove that our idea is correct.
1.Further understanding of the degradation mechanism of this bacterium will be the main task in our project. We have determined the role of the oxidase in the biodegradation process through data analysis, but the subsequent degradation process is still unclear. Therefore, we will continue to find other important enzymes in the biodegradation process so that we could construct a better artificial metabolic pathway.
2. After the validation of the degradation capacity, the next step is to enhance the gene expression by promoter optimization so that we will be able to improve its degradation ability.
3.Also, the products of degradation could be reused to produce high value-added products, such as PHA & CoA. Our plan is not only to degrade PE, but also to make it a new energy source and make full use of material.