Everything started from a nightmare which has being haunting one of our group members for years—the notorious Rhinitis. Therefore he has to carry a whole package of tissue with him whenever and wherever he goes. As he consuming increasing amount of tissue but having trouble finding a quick solution for Rhinitis, he questioned himself: is there anything he could do for all those trees vanished? Could synthetic biology offer a better solution for this scenario? So our team looked into paper recycle industry.
Coincidentally, wastepaper recycling industry is confronted with a serious problem: the inevitable keratinization during the recycling process, which results in the shortening of the cellulose fiber length and subsequently generating paper with lower quality.
Thus the demand seems quite clear —adding biomaterial to improve quality. It is the renowned bacterial cellulose(BC) that catches out attention, for many of its extraordinary properties. Furthermore, we hope to utilize the less useful shortened cellulose mentioned above as the raw material to produce BC in situ after separation of short and long fiber by filtration.
Recycled Paper Market Analysis
Under the popularization of circular economy around the world, the recycling of waste pulp, a green raw material for papermaking, has been given more and more attention, and consequently, the demand for waste paper has been rising substantially, which also promoted the growth of the global waste paper recovery rate.
Statistics shows that the global waste paper recovery has reached 250 million tons in 2018. Due to its complete waste paper recycling system, Japan leads the world in both recycling rate and utilization rate, with 81.5% recycling rate and 64.3% utilization rate. While paper utilization rate can not match recycling rate, and resources can’t be optimally allocated mainly due to the increasing proportion of short fibers in paper recycling.
The Economic Value of BC
Bacterial cellulose, hereafter this text will be abbreviated as BC, has the same chemical composition and structure as plant cellulose in pulp, but it has many advantages over plant cellulose: high purity, high degree of polymerization and crystallinity, high water holding capacity, good biocompatibility and biodegradability. As a porous reticulated nano-biopolymer, BC can be used as value-added medical materials, multi-functional textiles, functional food, electromagnetic materials, wastewater treatment filter materials and so on. In any way, BC has broad application prospects in various fields.
How does the Paper Transformer work？
Our project can be summarized as three parts—degradation of short fibers in waste pulp, synthetize of BC from former reaction products and applications of high value-added BC. Our chassis organisms was chosen from Acetobacter xylinum, Clostridium thermophilus and Escherichia coli, and the winner strain was E.coli for both cellulase and bacterial synthase has been characterized in E.coli in former iGEM projects. And we named our chassis organisms ‘Paper Transformer’ because we hoped it can transform inferior paper into paper with better quality and added value.. To begin with, Transformer secretes cellulose exoglucanase and endoglucanase, and hydrolyzes short fibers in the pretreated waste paper pulp into cellobiose. Thus, cellobiose can accumulate in fermentation broth. As cellobiose accumulating to a certain concentration, these two cellulases will be inactivated, Meanwhile, Transformer begins to express cellobiose phosphorylase and bacterial cellulose synthase, and continuously produces bacterial cellulose through the cellobiose → glucose → UDP Glucose → BC pathway.
A core part of our project is to achieve timing regulation in a single chassis organism. To achieve this goal, we will focus on realizing the following functions:
- Accumulation of cellobiose;
- Inactivation of cellulose endoglucanase and exoglucanase;
- Utilization of cellobiose
Just as transformers can transform from ordinary cars to super combat robots, our Transformer can transform waste paper into BC, which would play a big role in medical, environmental industries, textiles and other fields.