Isolation, screening and anodic biofilm potentials of electrogenic microorganisms from urine and waste water samples

Abstract

Microbial electrogenicity studies represent a new dimension in the development of renewable energy especially
bioelectricity and other bioelectrochemical energy applications. Bioprospecting for electrogenic species that can
subsequently be applied in this regard is ongoing in this budding field. In this study, bacteria were isolated from 5 human
urine and 5 waste water samples collected within the campus of Modibbo Adama University of Technology in Yola. Pure
cultures were screened for electrogenic activities by the 120 hour-Open Circuit Voltage (OCV) versus time determination
using glucose minimal salt medium in a dual-chambered microbial electrochemical reactor connected to a digital mutimeter
system. Anodic biofilm production by the electrogenic isolates was determined using the crystal violet binding assay
method. A total of 37 bacteria were isolated from the samples out of which nine (9) were confirmed to be naturally
electrogenic, while artificial electrochemical inducements using methylene blue as a redox mediator revealed that 16 of
them were sub-electrogenic and 12 were non-electrogenic. The electrogenic isolates were identified as Pseudomonas
species (3 isolates with OCV of 351.00?1.73mV; 288.67?2.52mV; 282.33?3.21mV) followed by Enterobacter species
(221.00?2.65mV, 202.33?2.52mV), Bacillus species (182.00?2.65mV, 178.33?2.08). The least electrogenic isolates were
identified as Aeromonas species with OCV values of 128.00?4.36mV and 106.33?0.58mV. Anodic biofilm production was
highest with Pseudomonas species followed by Enterobacter, Aeromonas and Bacillus species respectively. The anodic
biofilm production yield was an indication of the electrogenic mechanism adopted by the isolates. These strains can be
further studied along the line of electrogenicity to enhance favourable application in bioelectricity generation.