Description
Background & Investigation
Paper plays an extremely important role in human daily life. No one could ever imagine what would happen without the presence of paper. In 2018, around 422 million metric tons of paper were consumed globally. In the future, the amount of paper people consume is expected to grow steadily, reaching approximately 461 million metric tons in 2030. Paper are made from trees, which means that mammoth amount of trees will be cut off. Loss of trees will cause many environmental issues such as climate change, flooding, increased greenhouse gases and a host of problems for indigenous people.
Why we are doing this
While doing a geography project around school, part of our iGEM teams had discovered that there were many papers that had only been used one one-side and was thrown away into the recycle box. However, it is a really long process to recycle paper and it is also a burden for school to purchase paper from time to time. In a larger perspective, recycle paper can also provide environmental issues from happening. After doing the pre-experiment, we found out that recycled paper doesn’t not have a smooth surface and the recycling process needs to be more environmental-friendly as well.
Based on these two problems, we are considering that whether we can use synthetic biology to enhance the quality of recycled paper.
Source:https://www.statista.com/statistics/1089078/demand-paper-globally-until-2030/
Image:https://blog.manetmobile.com/wp-content/uploads/2019/02/book-collection-education-159751-1.jpg
Image:https://www.controlnroll.com/what-happens-to-paper-after-it-is-put-into-the-recycle-bin/
Design
First Part
As we have already mentioned in abstract, although our technology has improved a lot, the quality of recycled paper cannot compete with first-hand paper. So, we designed an experiment in order to test if we can improve the quality of recycled paper. The additives we chose to use are sericin and chitosan. According to our research, sericin can make recycled paper softer and more resilient while chitosan can make recycled paper harder and increase folding endurant.
Sericin is a complex protein produced by silk moth. Two genes encode sericin, Ser1 and Ser2. The different molecular weight sericin are the products of different splicing events at the transcript level. Some conformation studies with sericin from the silk gland of B.mori or regenerated sericin from B. mori cocoons suggested a random coil structure. However, the samples used in these studies were mixtures of the various native sericin proteins, therefore the structure of the individual proteins is unknown and the contribution of specific sequences toward secondary structure is not confirmed. Therefore, to better understand sericin structure, interactions between sericin and fibroin, and the biological relevance of sericin in fiber structure, high molecular weight pure sericin-like proteins are required. One clue suggests that Ser1, the encoding of sericin consists of 70 repeats of the 38-amino acid motif:
SSTGSSSNTDSNSNSVGSSTSGGSSTYGYSSNSRDGSV.
The molecular mass of sericin 1 proteins is 76–284 kDa. Hence, a sericin-like protein can be synthesized based on this 38-amino acid motif.
We constructed the pET28a(+) plasmid for E.coli to express sericin. In the first test, we added only one repeat in the multiple cloning site of the plasmid to form pET-28a(+)-Ser-01. The functional part is composed of T7 promoter-6xHis-repeat-6xHis-T7 terminator.
In order to imitate the original protein with multiple repeat inside its sequence, we decided to add eight repeats in the multiple cloning site of the plasmid to form pET-28a(+)-Ser-08. Among each repeat, we used the previous linker part BBa_K243004 to link each repeat. The functional part is composed of T7 promoter-6xHis-[repeat-Linker BBa_K243004]( for 8 times )-6xHis-T7 terminator.
