Ocean Plastic Pollution
Plastic pollution is recently become the major problem in the waste management, since there are around 275 million metric tons of them generated around the world in 2010. Indonesia itself is the second biggest source contributor of plastic waste in the ocean, with an estimation of 0.48 – 1.29 million metric tons in 2010. Why does the plastic waste end up in the ocean? Mismanagement of the plastic waste in the landfill is one of the major cause. The plastics can be carried by wind and rain into rivers, then flow into the sea. Many rivers around the world carry about 1.15-2.41 million tons of plastic waste, transporting them into the ocean . One of the real-world examples happen around our city, Bandung, in the landfill of Sarimukti. The majority of the waste is plastics, stacked into mountains of dirt and trash. When the rainy season is coming, the rain washed out the plastics left behind by the treatment facility into the river nearby. Eventually, these are the plastics that will reach the ocean.
After reaching the ocean, the plastic waste is available in many forms. It can be found at the surface, in the depths, even in the sediment. Plastic bags need up to 20 years to break down completely, while plastic bottles need a hefty 450 years to break down. But actually, one of the pressing concerns is the microplastics. Microplastics formation is caused by combination of physical, chemical, and biological processes. Using modelling approach, it has been estimated that around 15-51 trillion microplastic particles have accumulated in the ocean .
A number of studies have revealed the harmful impacts of microplastics on the marine biota. Those covers the physical-chemical effects of microplastics ingestion, and the transport of invasive species. Direct effects of ingestion of microplastics is the blockage of intestinal tract which impedes the organisms from taking in more resources. Microplastics also contain harmful chemical such as Bisphenol-A (BPA) which is originated from parent plastics during manufacturing process. They also provide raft substrates for various fauna and microbes, and transporting them to regions where they were not existing before.
There are many ways to control plastic waste from going in to the ocean. Better recycling system and waste treatment are handful of solution to be implemented. But how about the plastic that is already being in the ocean? How about the microplastics which is already broken down and difficult to find, yet still threatening the ocean ecosystem? We present DewaRuci, engineered Escherichia coli which have ability to locate the microplastic and degrade them effectively through biofilm-based degradation. DewaRuci is based on based on the Indonesian Navy barquentine ship which was used as a sail training vessel for naval cadets and is the largest tall ship in the Indonesian fleet. Dewaruci also serves as a goodwill ambassador for Indonesia to the rest of the world.
This module uses indirect detection of organic pollutants in the plastic surface, with pSal inducible promoter.
The degradation module
Approach that we’re using is PET-plastic degradation using PETase enzyme from Ideonella sakaiensis.
The biofilm-enhancing module
We want to see if increased expression of biofilm will enhance the degradation efficiency. The gene used is transcriptional activator NhaR, which will affect the expression of pgaABCD operon required for production of biofilm adhesin poly-β-1,6-N-acetyl-D-glucosamine.
The salt-tolerance module
Because we need our E. coli to be resistant to extreme environment, we also used irrE gene from Deinococcus radiodurans to protect them from salt, oxidative, and thermal shock.
The converter module
One of the byproduct of PET-degradation is ethylene glycol, which is toxic to bacteria at certain concentration. We tackle this problem by expressing glycolaldehyde reductase and glycolaldehyde dehydrogenase, which will convert ethylene glycol into nontoxic glycolate – metabolite found in the Krebs cycle.
The genetic containment module
If we release the engineered organism to nature, there are possibilities of genetic makeup contamination of natural ecosystem. We use EndA endonuclease from Vibrio fischeri that will cleave extracellular DNA going outside of the cell.