Living Photosynthetic Bacteria for Sustainable Bio-Photovoltaics

Solar energy is the most abundant energy source on Earth and will be the key source of electricity in a low-carbon future. [1] The development of solar power technologies is considered one of the best options to meet the increasing future energy demand. [2] To maximize the potential of solar power, new materials are needed to harvest and convert solar energy alongside the current photovoltaic technologies. [3] As new and optimized material, photosynthetic bacteria can pioneer the cutting-edge novel strategies for environmentally safe and cost-effective energy production. [4]<br/><i>Rhodobacter (R.) sphaeroides </i>is a versatile photosynthetic purple non sulfur bacteria able to harvest sunlight, and particularly the Near Infrared region, and perform an efficient photochemical energy transduction. Bio-hybrid architectures [5-7] have been designed aiming at photovoltage generation using the light harvesting abilities of photosynthetic components. Here, whole metabolically active photosynthetic cells of the wild type and the carotenoidless mutant strain of <i>R. sphaeroides</i> were implemented in a two electrodes device configuration, obtaining a positive variation of the generated photovoltage upon lighting cycles. The higher photovoltage output and the ability to elicit a constant voltage output in slow lighting conditions of the mutant strain, almost three times higher than the voltage amplitude obtained with wild type cells. Photosynthetic bacterial cells were also implemented in a light-driven three-electrode actual device, as electrolyte-gated organic transistors and in a power cell exposing bacteria to direct sunlight illumination.<br/><br/>[1] Rhodes, C.J., Solar energy: principles and possibilities. <i>Sci Prog </i>2010, <i>93</i> (Pt 1), 37-112.<br/>[2] Pourasl, H.H.; Barenji, R.V.; Khojastehnezhad, V.M., Solar energy status in the world: A comprehensive review. <i>Energy Reports </i>2023, <i>10</i>, 3474-3493.<br/>[3] Sekar, N.; Ramasamy, R.P., Recent advances in photosynthetic energy conversion. <i>Journal of Photochemistry and Photobiology C: Photochemistry Reviews </i>2015, <i>22</i>, 19-33.<br/>[4] El-Khouly, M.E.; El-Mohsnawy, E.; Fukuzumi, S., Solar energy conversion: From natural to artificial photosynthesis. <i>Journal of Photochemistry and Photobiology C: Photochemistry Reviews </i>2017, 31, 36-83.<br/>[5] Musazade, E.; Voloshin, R.; Brady, N.; Mondal, J.; Atashova, S.; Zharmukhamedov, S.K.; Huseynova, I.; Ramakrishna, S.; Najafpour, M.M.; Shen, J.-R.; Bruce, B.D.; Allakhverdiev, S.I., Biohybrid solar cells: Fundamentals, progress, and challenges. <i>Journal of Photochemistry and Photobiology C: Photochemistry Reviews </i>2018, <i>35</i>, 134-156.<br/>[6] Di Lauro, M.; Buscemi, G.; Bianchi, M.; De Salvo, A.; Berto, M.; Carli, S.; Farinola, G. M.; Fadiga, L.; Biscarini, F.; Trotta, M., Photovoltage generation in enzymatic bio-hybrid architectures. <i>MRS Advances</i> 2020, 5 (18-19), 985-990.<br/>[7] Di Lauro, M.; la Gatta, S.; Bortolotti, C.A.; Beni, V.; Parkula, V.; Drakopoulou, S.; Giordani, M.; Berto, M.; Milano, F.; Cramer, T.; Murgia, M.; Agostiano, A.; Farinola, G.M.; Trotta, M.; Biscarini, F. A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light. <i>Advanced Electronic Materials </i>2020, 6 (1), 1900888.