Hydrogen is a critical energy carrier to achieve greenhouse gas emission neutrality for its zero-carbon emission after combustion, considering about 90% of the annual global CO2 emissions are related to energy demand (International Energy Agency, 2019). While the production of H2 is still mainly based on fossil fuels, the research team Biophotovoltaics (BPV) is aiming to develop a unique light-driven carbon-sink biological approach for hydrogen production with low energy demand and high light-to-energy efficiency.
The concept of BPV is to directly couple the sunlight and water to H2 using natural oxygenic photosynthesis. It is a biohybrid system integrating cyanobacteria into an electrochemical cell. Briefly, the electrons released from water split by the cyanobacteria using sunlight are captured by the anode and then transferred to the cathode for pure H2 production. CO2 is fixed for biocatalyst (i.e. biomass) reproduction. By directly coupling the photosystem to H2 production, BPV requires much less energy input to drive hydrogen evolution reaction compared to the classic electrolyser (for “green hydrogen” production), and also exhibits high light-to-energy efficiency and high purity of H2, which are the typical intrinsic limits of other biotechnological H2 production approaches.
Despite of its promising potentials, BPV also faces some challenges. For instance, the extracellular electron transfer (EET) pathways from the intracellular photosystem on the thylakoid membrane are much more complicated and dynamic compared to those for heterotrophic electrogens based on cytoplasmic membrane proteins. The hard-to-achieve metabolic steady status of oxygenic cyanobacteria (e.g. Synechocystis) also makes the comparative and quantitative analysis of the bacterial behaviors in BPV quite difficult. The research team BPV is dedicated to tackling these fundamental scientific challenges to realize the BPV technology for practical applications. By collaborating with research partners within and outside the department, our team applies an interdisciplinary approach, from biology, material science to electrochemical process engineering, to quantitatively identify the key limiting factors and then overcome them by rational design of the cyanobacteria and the BPV system. Our long-term mission is to provide an eco-friendly BPV-based H2 solution for future energy demand.
LC-MS/MS based proteomics analysis of Synechocystis sp. PCC6803 phenotype in biophotovoltaics
Understanding how Synechocystis behaviours exposing to anodic electron sink plays a central role in quantitative biophotovoltaics research and subsequent rational system engineering. The project aims to apply the lab-established LC-MS/MS methods to quantitatively address the proteome changes steered by the electrode. Two objectives will be focused on in this project, with each of them corresponding to an individual master thesis:
- Global proteome analysis focusing on cellular metabolism in response to different working conditions (e.g. light, working electrode potential, etc);
- Membrane proteome analysis with the target to identify key redox proteins involved in extracellular electron transfer or transporters responsible for mediator transportation.
CRISPR-based interrupting system (CRISPRi) for Synechocystis sp. PCC6803
This project is aiming to develop the CRISPRi system to targeted interrupt specific protein(s) of Synechocystis to identity its (their) functions involved in the performance of the microorganism in a biophotovoltaics system. The work will be based on a well-established system developed in KTH Sweden (Yao, L., et al. (2016). ACS Synthetic Biology 5(3): 207-212; Yao, L., et al. (2020). Nature Communications 11(1): 1666) and localize it into our lab. Essential strains and plasmids were kindly provided by Prof. Hudson. As a proof-of-concept study, the initial target will be to create a Synechocystis mutant with inducible inhibition of the photosystem II (PSII) protein complex. Different subunits of PSII should be tested and the time-course PSII activity (based on O2 evolution rate and PAM measurement) should be traced after induction.
Gas composition analysis using membrane-inlet mass spectrometry
This project aims for developing a quantitative protocol to trace the gas composition of the medium in BPV reactor. A membrane-inlet mass spectrometry will be used, and oxygen and CO2 are of particular interest in this project. Oxygen evolution rate and CO2 assimilation rate are the key parameters to be determined. The research question involved in this project is how the photosynthetic and carbon assimilation activities of Synechocystis sp PCC6803 are impacted by the anodic electron sink in BPV system.