Paper Recycling with Enzymes
An impressive 214,364,825 tons of paper were recycled in 2013 worldwide. The most relevant step for the quality of recycled paper is the removal of ink (deinking). Although chlorine has been widely banished from deinking, the process remains environmentally and economically challenging. In particular, the production of chemicals employed for deinking is energy intensive and the by-products are environmentally harmful. We want to tackle this issue by using enzymes instead of chemicals.
Enzymes have already been shown to efficiently deink paper. However, application of enzymes in industry requires a highly optimised procedure. For this, it would be ideal to develop a cheap and easy to use system based on continuous secretion of various enzymes, which could be then used to test their deinking efficiency.
Our approach relies on gene expression in Bacillus subtilis, as this species naturally secretes large amounts of proteins into its surrounding. Using B. Subtilis allows us to purify or even use our enzymes directly from the supernatant. We managed to developed a expression plasmid for B. subtilis for the iGEM parts registry, which allows replication in Escherichia coli, as well as in B. subtilis. Last but not least, bacterial supernatants containing the expressed enzymes have been tested in the deinking process.
We aim to revolutionize paper recycling by integrating all of the above aspects into one procedure that is simple enough to be applied not only in centralized recycling facilities, but also for implementation on a smaller scale. This would dramatically reduce the distance paper waste needs to be transported, thereby reducing the carbon footprint of the entire process. Our system is the prerequisite to improve enzymatic deinking to a level where it is not only industrial feasible, but outperforms chemical deinking on this scale.
B. Subtilis group concerned themselves with creating a "cell factory" for the wished enzymes, secreting them to the surrounding medium.
Cloning is used to put genes of interest (GOI) into a new recombinant DNA plasmid that can be replicated by a host organism. Our GOI are genes which code for enzymes used in deinking, and our host organisms are B. subtilis and E. coli. A plasmid was designed to work in both.
Deinking (your king) is the art of seperating ink particles from paper fibers. While currently chemicals are applied for this method, we try to establish assays, which make it possible to examine the deinking properties of enzmyes.
In order to guarantee the efficiency of our own secreted enzymes and find optimum environment in our project set up for the own enzymes and bought ones, a functional enzyme assay is necessary.