Electron Mediation and Photocurrent Enhancement in Dunalliela salina Driven Bio-Photo Electrochemical Cells

Abstract

In recent years, finding alternatives for fossil fuels has become a major concern. One promising solution is microorganism-based bio-photo electrochemical cells (BPECs) that utilize photosynthetic solar energy conversion as an energy source while absorbing CO2 from the atmosphere. It was previously reported that in cyanobacterial-based BPECs, the major endogenous electron mediator that can transfer electrons from the thylakoid membrane photosynthetic complexes and external anodes is NADPH. However, the question of whether the same electron transfer mechanism is also valid for live eukaryotic microalgae, in which NADPH must cross both the chloroplast outer membrane and the cell wall to be secreted from the cell has remained elusive. In this work, we show that NADPH is also the major endogenous electron mediator in the microalgae Dunalliela salina (Ds). We show that the ability of Ds to tolerate high salinity enables the production of a photocurrent that is 5–6 times greater than previously reported for freshwater cyanobacterial-based BPECs in the presence or absence of exogenous electron mediators. Additionally, we show that the electron mediator Vitamin B1 can also function as an electron mediator enhancing photocurrent production. Finally, we show that the addition of both FeCN and NADP+ to Ds has a synergistic effect enhancing the photocurrent beyond the effect of adding each mediator separately.

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

“…A very important technical factor that can enhance the electrical current production is the ionic strength of the electrolyte solution. Increased salinity can increase the conductivity of the BPEC ( Shlosberg et al, 2021b ). For this reason, there is a significant advantage for BPECs that are based on marine cyanobacteria, among these species is Acaryochloris marina .…”

“…Among the most common microalgal species that have been used in BPECs are Dunaliella salina and Chlorella sp. ( McCormick et al, 2011 ; Shlosberg et al, 2021b ; Herrero-Medina et al, 2022 ), which are also cultivated in industrial facilities for other purposes like the production of bio-oils, food additives and cosmetics ( Yang et al, 2011 ; Barba et al, 2015 ; Vieira et al, 2020 ). Photosynthetic microorganisms use only a small percentage of the energy obtained via photosynthesis for EET.…”

“…Blue arrows represent the direction of the electron transport between components. Photocurrent production in BPEC can also be conducted with green micro-algae (Fischer, 2018;Thangam et al, 2021;Shlosberg et al, 2021b;Herrero-Medina et al, 2022). In the eukaryotic photosynthetic microorganisms, the thylakoid membranes are compartmentalized to the chloroplast.…”

“…In BPECs, photosynthesis is harnessed to convert the light energy to electricity or to produce high-energy chemical compounds. BPECs can utilize isolated photosynthetic components such as thylakoid membranes ( Pinhassi et al, 2016 ), chloroplasts ( Hasan et al, 2017 ), photosystem I (PSI; Gizzie et al, 2015 ; Caspy et al, 2021 ; Toporik et al, 2021 ; Wang et al, 2022 ), photosystem II (PSII; Sokol et al, 2018 ; Hartmann et al, 2020 ; Zhang and Erwin, 2020 ; Shoyhet et al, 2021 ) or intact living photosynthetic microorganisms ( Shlosberg et al, 2021b ; Bombelli et al, 2022 ; De Moura Torquato and Grattieri, 2022 ). Unlike non-photosynthetic bacteria, the photosynthetic organisms possess the mechanisms needed to utilize sun light and convert it to electricity ( Chen and Blankenship, 2021 ).…”

Identification of bacteria by poly-aromatic hydrocarbons biosensors

“…[34][35][36][37][38][39][40][41][42][43][44][45][46] Microorganisms are consist of several components such as the amino acids Tyrosine, Tryptophane, and Phenylalanine, or metabolites such as NADPH that can be detected based on their intrinsic fluorescence. [47,48] DNA also fluoresce under UV-VIS irradiation, however, its native emission is usually too low to be detected. Amplification of DNA fluorescence can be done by labeling it with fluorescent dyes such as SYBR that amplify its emission intensity.…”