Nanobionics to empower photosynthesis and productivity of microalgae

Project leaders

Mayadimova Lambreva, Andrei Borisovich Rubin

Agreement

RUSSIA - RFBR-suspended - Russian Foundation for Basic Research

Call

CNR/RFBR 2015-2017

Department

Biology, agriculture and food sciences

Thematic area

Biology, agriculture and food sciences

Status of the project

New

Research proposal

Large-scale cultivation of microalgae in photo-bioreactors plays an important role in the production of vast number of bio-based products. One of the main problems in high-density-cultured algal bioreactors is the reduction of production yields due to occurrence of strong light-shading. By increasing the energy available for the photosynthesis, the capacity of algal cultures to produce biomass, biofuels or high-value compounds can be significantly increased. This project proposes to use a nanobionic approach to overcome the light-shading issue in high-density cultures. We intend to realize nanobionic Chlamydomonas reinhardtii algae, in which the light harvesting capacity is enhanced by the introduction of single-walled carbon nanotubes (SWCNs) into the chloroplast. SWCNs are highly efficient in light energy capturing and have wider absorption spectrum compared to the chloroplast antenna pigments (1). In addition, the SWCNs are able to transfer the absorbed energy to the photosynthetic complexes with consequent increase in the photosynthetic activity (2). The main objective of the research is to empower the photosynthesis of the unicellular green algae by enlarging the light spectrum region and by increasing the quantity of the energy available for its photosynthetic reactions. To reach our goal, the nanobionic SWCNs-algae system will be characterized and improve to achieve the best performance of the system. The efficiency of SWCNs uptake will be evaluated by testing the capability of SWCNs having different dimensions and electric charges to penetrate the cell. The functionalized SWCNs and their internalization will be studied by high spatial-resolved techniques (SEM, TEM, Raman spectroscopy). In addition, the SWCNs effects on algae growth, fitness and photosynthesis activity will be evaluated in order to identify the optimal SWCNs concentrations. In the best performing SWCNs-algae system, the energy transfer between the SWCNs and photosynthetic complexes, and its effects on the primary photochemistry will be evaluated by various time-resolved chlorophyll fluorescence techniques able to provide comprehensive view of PS2 and PS1 photosynthetic events. Moreover, the capacity of the SWCNs to enhance light harvesting will be assessed by measuring the electron transport and O2 production rates at different light quality and quantity.
The routine functioning of the plant photochemistry is accompanied by the generation of reactive oxygen species (ROS), which compromises the efficiency of the energy conversion. Taking advantage of the SWCNs ability to transport small molecules through the cellular barriers, we propose to deliver into the chloroplast effective ROS scavengers, such as nanoceria (NC) or nanodiamond (ND). By introducing NC or ND at the site of ROS generation, the free radicals can be trapped before damaging nearby pigments, reaction centres and photosynthetic proteins. We will evaluate if the addition of ROS-scavenging components to the SWCNs will improve the SWCNs-algae system.
Under specific conditions, the algae are able to switch from oxygen (normal photosynthesis) to hydrogen production, thus diverting the products of its primary photochemistry to the proton reduction. Therefore, the potential of the nanobionic SWCNs-algae system will be tested for its promising application in the green energy production. In particular, the possible improved ability of the SWCNs-algae system to produce hydrogen in liquid and immobilized cultures with different cells density will be tested. Cells will be entrapped in alginate matrix as cells immobilization has been suggested to increase the hydrogen production rates (3). The PS2 activity is essential for the duration and efficiency of the hydrogen production. For this reason, the capacity of NC and ND to meliorate the PS2 stability will be evaluated in both, liquid and immobilized cultures. In addition, the effect of different factors influencing the hydrogen production yield (light spectrum, pH, PS2 and PS1 activity, starch accumulation, etc.) will be examined in order to optimize the experimental conditions for more effective proton reduction.
The proposed research will be the first attempt to apply the nanobionics approach to whole organism to enhance its photosynthetic performance. This study will bring new knowledge about the SWCNs effects of algal primary photochemistry and energy transfer between the SWCNs and the photosynthetic complexes. In addition, our results will deeper the understanding of the SWCNs cell uptake and localization. Finally, the successful realization of this project could open new opportunities for more efficient use of the photosynthesis-based systems in the sustainable production of energy, biomass and high-value compounds.
This project will involve scientists from two Italian Institutions, CNR and University of Rome Tor Vergata, and Moscow State University (MSU) from the Russian Federation. It will strengthen an already existing collaboration among the research groups of CNR and MSU. Moreover, the positive outcome of this project is assured by the involvement of researchers with extensive experience: i) in the synthesis, characterization and manipulation of carbon-based nanomaterials (Tor Vergata); ii) in the characterization, manipulation and application of C. reinhardtii in different research fields (nutraceutics, space research, bio-sensing devices) and iii) in hydrogen photo-production process (MSU). In addition, both research groups (CNR, MSU) have deep understanding of the primary photosynthetic reactions and master various techniques for their characterization.
References: 1. Synth. Met., 1991, 103:2555.
2. Nature Mater., 2014, 13:400.
3. Biotechnol. Bioeng., 2009, 102:50.

Research goals

We propose an innovative approach to solve the light-shading problem that is specific to high-density-cultured algal bioreactors. We suggest the utilization of nanobionic SWCN-algae with enhanced ability to utilize the energy of the available light. In particular, the main objective of the research is to boost the photosynthetic performance of the unicellular green alga C. reinhardtii by enlarging the light absorption spectrum and by increasing the quantity of the energy available for the photosynthetic reactions. To reach the aim, the Italian (IU) and Russian Units (RU) will collaborate to thoroughly characterize and implement the novel SWCNs-algae systems. We will examine the SWCN's efficiency to enhance the algal capacity of light energy harnessing, and evaluate their benefits on algae's growth rate, fitness and photosynthesis. Moreover, the potential of the nanobionic SWCNs-algae systems to enhance green energy production yields will be studied. In particular, we intend to evaluate the capacity of the SWCNs-algae systems for H2 production in both, liquid and immobilized cell cultures. Finally, this project will give the opportunity to foster the already existing collaboration between the two partners and will establish the bases for common future projects.

Last update: 16/04/2024