Team:USTC/HP/Gold Integrated
We recognize the vital importance of how our project can actually be put into practice to promote social development, and the best way is to find out what the problem is and what people really need. Specifically,
1.We studied to lots of previous works in biological cathode to find out current limits of microbes in MES and got inspiration from the work of Prof. Yang Peidong and other researchers [1].
2.After aiming our project at optimizing biological cathode to make biological synthesis more efficient, we went to a pharmaceutical company to seek advice on project design to better serve the needs of industrial production.
Previous Studies Analysis
We studied lots of previous works in BESs(Bio-electro-chemical systems) and MES(Microbial electro-synthesis) to find out current limits in MES and inspirations in possible ways to solve them.
BESs have both biological advantages such as self-replication, and electrochemical advantages such as a mass-free supply of redox equivalents and the use of the cheapest redox equivalent-the electron [2]. In particular, MES is a promising technology as a cell factory for bio-commodities production because this can produce organic matters with microbial electro-catalysts [3].
In order to increase process effectiveness and to evolve from lab-scale to industry-scale, MES researchers have studied not only microorganisms, but also electrochemistry, controlled substrate flux, end-product toxicity, and designed new reactor and electrode. Among them, the electrode and potential value are strongly related to metabolic aspects of microorganisms in MES. In spite of many trials for understanding and improving non-microbial factors, the restricted intrinsic performance of wild microorganisms (e.g., lack of electron transfer channels, insufficient biofilm formation, and unsatisfactory production rate) still remains the main challenge for industry-level development of bio-commodities production. In order to overcome these limitations, it is necessary to understand electron transfer of microorganisms and explore novel genetic engineering approaches [4].
We came up with a new solution by enriching ways of electron transfer channels with this novel genetically-engineered microorganism—PELICAN.
We found inspiration of Prof. Yang Peidong’s work, which shows CdS (Cadmium Sulfide) in the form of nanoparticles on the surface of the cell can serve as an electron donor to increase the efficiency of microbial synthesis when excited by light [1]. We also know that MTR (Metal Reductase) system naturally existed in cell membrane in Shewanella can transfer electrons from outside to inside the cell, and we investigated the theoretical effectiveness of using CdS to conduct electrons to MTR and decided it is a feasible way. Thus we combined two systems together in E. coli to establish a double electron channel where electrons can either enter the cell through MTR system or more probably through CdS to MTR then into the cell. The latter is expected to considerably increase the efficiency of electron transfer with extra energy resources--light. In this way, we expect to push MES a step forward for industrial use by improving the restricted intrinsic performance of microorganisms we use.
Communication With Pharmaceutical Company
The company roots in Hefei and has a complete pharmacy chain from research development, production to market. Medication includes both chemicals and bio-antibodies. We presented our ideas and investigation, and thanks for their kind interpretation in this field and useful advice, we learned so much about bio-pharmacy and organized our project in a more practical way. Key points of our exchange are as follows.
Firstly it’s stressed that bio-pharmaceuticals are taking up greater percentage in medication, and according progress is desired by both the market and the public. Bio-medicine is generally more environmental-friendly, and is more specifically aimed for a disease. It would be easier to seek funds and get things done if we focus on optimizing the production of some specific bio-drug with the project, or organizing a universal platform that enables various potential use.
Choosing a microbe competent for industrial use is important. For more complex bio-products like antibodies, bacteria are replaced by mostly yeast and other platforms are still under research. Learning that compared with other bacteria, E-coli is the most commonly used with well exercised techniques and relatively simple condition demands for industrial use, we decided to establish our system in E-coli.
However, a problem follows that the CCM system is off in E-coli when oxygen is present, which might lower the productivity of E-coli by limiting its growth with oxygen present. To provide an alternative for this potential problem, we decided to establish a plasmid with CCM and a specially designed operator to allow its expression with oxygen.
Reference:
[1] Sakimoto, K. K., Wong, A. B., & Yang, P. (2016). Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production. Science, 351(6268), 74-77.[2] Krieg, T., Sydow, A., Schröder, U., Schrader, J., & Holtmann, D. (2014). Reactor concepts for bioelectrochemical syntheses and energy conversion. Trends in biotechnology, 32(12), 645-655.
[3] Schröder, U., Harnisch, F., & Angenent, L. T. (2015). Microbial electrochemistry and technology: terminology and classification. Energy & Environmental Science, 8(2), 513-519.
[4] Shin, H. J., Jung, K. A., Nam, C. W., & Park, J. M. (2017). A Genetic Approach for Microbial Electrosynthesis System as Biocommodities Production Platform. Bioresource Technology.
