Roots fuel cell produces and stores clean energy

Abstract

In recent years, extensive scientific efforts are conducted to develop clean bio-energy technologies that have the potential to compete with the contaminating fossil fuels. Electricity production was previously generated from photosynthetic organisms in bio-photo electrochemical cells (BPECs), and microbial fuel cells (MFCs). The main approach of such methods was to exploit the ability of the organisms to perform external electron transfer (EET) to reduce the anode of an electrochemical cell. By far, these methods were applied to microorganisms, seaweeds, and plant leaves. The ability of roots to perform EET was applied in solutions that consist of molecular electron acceptors, however, it was not used for electricity production yet. In this work, we integrate green onion roots in a bio-electrochemical cell and show that it can produce continuous bias-free electric current for more than 24 h. This current is enhanced upon irradiation of light on the onion leaves. We apply 2D fluorescence maps to show that NADH serves as a major electron mediator between the roots and the anode, while its concentration in the external root matrix is increased upon irradiation of the leaves. Direct electricity production from roots may be integrated with soil based MFCs or plant leaves-based BPECs and pave the way towards the establishment of novel renewable energy technologies.

Redox-active molecules in bacterial cultivation media produce photocurrent

“…Previous studies have reported the utilization of the protein Cytochrome C (Cyt) as an indicator for the presence of reducing molecules in a solution [31]. The absorption spectrum of fully oxidized Cyt shows a single peak at λ=475 – 600 nm with a maximum at 530 nm.…”

“…Absorption of LB fully oxidized Cyt and a mixture of Cyt +LB after 30 incubation. The intensity increase at 550 nm indicates Cyt reduction [31] Absorption spectra of LB (black), Cyt (red), and Cyt + LB (blue). b Average absorption at 550 nm of LB (black), Cyt (red), and Cyt + LB (blue).…”

“…In this approach, organic material is released from degraded plant roots and can be used for bacterial cultivation in the soil. Regardless of the soil bacteria, roots can also perform EET [30] and apply as electron donors in bio-electrochemical cells [31]. The current production from bacteria can be enhanced using a biofilm architecture that is in close association with the anode [32].…”

Non-photosynthetic bacteria produce photocurrent mediated by NADH

“…Recent works have reported the release of the redox active molecules Nicotinamide adenine dinucleotide (NADH) and Nicotinamide adenine dinucleotide phosphate (NADPH) from various organisms such as cyanobacteria 25,30 , microalgae 26 , seaweeds 32 , plant’s leaves 29,34,36 , roots 38 and sea anemones 39 . These molecules can apply as electron mediators in bio-electrochemical cells catalysing electrons transport between the respiration and photosynthetic pathways of the cells and the external anode.…”

Photocurrent production from cherries in a bio-electrochemical cell

“…The photocurrent production from seaweeds and plants is about 1000 times greater than reported for micro-organisms [35]. Plants' roots secrete reducing molecules [36,37] that can also be utilized for electrical current production in BECs [38]. Rather than direct electricity production, the degradation of roots in the soil releases organic compounds that can be used to feed bacteria in soil MFCs [39].…”