A miniaturized bioelectricity generation device using plant root exudates to feed electrogenic bacteria

This paper presents a miniaturized plant-microbial fuel cell (mPFMC) as an assay tool that can examine different combinations of plants and electrogenic bacteria to maximize bioelectricity generation. The plant is grown in a miniature plant growth chamber (PGC). Root exudates of the plant provide carbon-containing organic matter to support the catalytic reaction of the bacteria inoculated and grown on the carbon cloth anode of a miniature microbial fuel cell (MFC). The mPFMC utilizes a semipermeable hydrophilic filtering membrane to separate the PGC from the MFC. This membrane allows retaining the bacteria inside the MFC for inoculation and growth and prevents them from entering the PGC; however, the membrane still permits the root exudates into the MFC as the sole carbon source to the bacteria grown on the anode of the device. A pilot proof-of-concept study was conducted to validate the mPMFC, by using it to examine electricity generation of the device with different varieties of model organisms, including rice plant cultivars Kitaake and IR24, and bacterial species Shewanella oneidensis strain MR-1 and Pseudomonas aeruginosa strain PA14. The plant cultivars were grown hydroponically without using soils, thus eliminating the effect of soil microorganisms and nutrients on the bioelectricity generation of the device. The present mPFMC has high compactness with the dimensions of 25 × 25 × 29 mm3, consumes only 3 mL volume of plant growth medium and less than 1 mL volume of anolyte and catholyte each, and produces electricity within only several hours after the plants are loaded into the device. The present technology will allow large-scale parallel screening of different combinations of small plants and electrogenic bacteria and their strains for bioelectricity generation.