Harnessing photosynthesis to produce electricity using cyanobacteria, green algae, seaweeds and plants

Abstract

The conversion of solar energy into electrical current by photosynthetic organisms has the potential to produce clean energy. Life on earth depends on photosynthesis, the major mechanism for biological conversion of light energy into chemical energy. Indeed, billions of years of evolution and adaptation to extreme environmental habitats have resulted in highly efficient light-harvesting and photochemical systems in the photosynthetic organisms that can be found in almost every ecological habitat of our world. In harnessing photosynthesis to produce green energy, the native photosynthetic system is interfaced with electrodes and electron mediators to yield bio-photoelectrochemical cells (BPECs) that transform light energy into electrical power. BPECs utilizing plants, seaweeds, unicellular photosynthetic microorganisms, thylakoid membranes or purified complexes, have been studied in attempts to construct efficient and non-polluting BPECs to produce electricity or hydrogen for use as green energy. The high efficiency of photosynthetic light-harvesting and energy production in the mostly unpolluting processes that make use of water and CO2 and produce oxygen beckons us to develop this approach. On the other hand, the need to use physiological conditions, the sensitivity to photoinhibition as well as other abiotic stresses, and the requirement to extract electrons from the system are challenging. In this review, we describe the principles and methods of the different kinds of BPECs that use natural photosynthesis, with an emphasis on BPECs containing living oxygenic photosynthetic organisms. We start with a brief summary of BPECs that use purified photosynthetic complexes. This strategy has produced high-efficiency BPECs. However, the lifetimes of operation of these BPECs are limited, and the preparation is laborious and expensive. We then describe the use of thylakoid membranes in BPECs which requires less effort and usually produces high currents but still suffers from the lack of ability to self-repair damage caused by photoinhibition. This obstacle of the utilization of photosynthetic systems can be significantly reduced by using intact living organisms in the BPEC. We thus describe here progress in developing BPECs that make use of cyanobacteria, green algae, seaweeds and higher plants. Finally, we discuss the future challenges of producing high and longtime operating BPECs for practical use.

Self-Enclosed Bio-Photoelectrochemical Cell in Succulent Plants

“…In our previous studies, ,, we showed that the source of the electrons harvested in BPECs from the water oxidation reaction performed by PSII. The addition of DCMU to the organisms was shown to inhibit photocurrent production in BPECs based on microalgae, seaweeds, and plants, indicating that DCMU penetrates into the chloroplasts and binds to PSII.…”

“…The results display accumulation of 0.3 and 0.175 μmol H 2 in light and dark operated BPEC, in a good correlation with the current formation. The Faradaic efficiency for the hydrogen production in dark and light was calculated as the ratio between the total current production divided by the number of In our previous studies, 23,26,27 we showed that the source of the electrons harvested in BPECs from the water oxidation reaction performed by PSII. The addition of DCMU to the organisms was shown to inhibit photocurrent production in BPECs based on microalgae, seaweeds, and plants, indicating that DCMU penetrates into the chloroplasts and binds to PSII.…”

“…17,24,25 In the case of some cyanobacterial-based BPECs, the addition of the Photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) can either increase the photocurrent production 16,17 or inhibit the photocurrent, 26 indicating that multiple pathways of EET may exist, depending on the BPEC operating conditions. 26 Unlike cyanobacterial-based BPECs, the addition of DCMU to microalgal-based BPECs clearly eliminates photocurrent production. 24 We have recently shown that BPECs are not limited to microorganisms and may also utilize seaweeds 27 or terrestrial and aquatic plants.…”

“…photosynthesis and are released to the extracellular solution, that serves as the electrolyte of the BPEC 17,24,25. In the case of some cyanobacterial-based BPECs, the addition of the Photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) can either increase the photocurrent production16,17 or inhibit the photocurrent,26 indicating that multiple pathways of EET may exist, depending on the BPEC operating conditions 26. Unlike cyanobacterial-based BPECs, the addition of DCMU to microalgal-based BPECs clearly eliminates photocurrent production 24.…”

Direct Electricity Production from Nematostella and Arthemia’s Eggs in a Bio-Electrochemical Cell

“…Recently, it was reported that bio-photo electrochemical cells (BPECs) are not limited to micro-organisms and can be based on photosynthetic macroorganisms such as seaweeds [ 27 ] and aqueous and terrestrial plants [ 28 ] as electron donors. Interestingly, macroorganisms-based BPECs have produced an electrical current in both dark and light that was about 100–1000 times greater than photosynthetic microorganisms [ 29 ]. Rather than using whole microorganisms in BECs, electrical current can be produced via photon excitation by utilization of isolated photosynthetic components in different levels of purification, such as Thylakoid membranes [ 22 ], Chloroplasts [ 30 ], and Photosystems [ 31 , 32 , 33 , 34 , 35 , 36 , 37 ].…”