From local bacterial communities to energy: application of microbial fuel cells in laboratory experimentation

ABSTRACT

It is well known that bacterial communities are an essential component to maintain the balance of terrestrial ecosystems due to the functions and services performed by microorganisms in the environment. The research seeking on alternative energy sources has shown that bacterial communities can bioconvert the chemical energy of an organic substrate into electrical energy, within devices known as microbial fuel cells. For this reason, this class project allows students of Biotechnology, Environmental Science, and Microbiology to apply the appropriate methodology to develop a class project throughout an environmental bacterial community capable of generating electrical energy.

INTRODUCTION

Microorganisms from phyla such as Proteobacteria, Firmicutes, Acidobacteria, and Actinobacteria have demonstrated significant relevance in various biotechnological applications; one of the most intriguing and innovative is the use of the microbial consortia as catalysts in a bioelectrochemical system (1, 2). Bacterial communities found in wastewater and natural sediments can act as biocatalysts for the oxidation of organic substrates when integrated into microbial fuel cells (MFC). These MFCs are not only capable of treating wastewater but are also applied in experimentation as a device capable of generating bioenergy (3).

In this context, this interdisciplinary laboratory project aims to enable students to operate an MFC to generate electrical current, allowing them to explore the bioenergetic potential of microbial consortia. This hands-on approach will provide students with a deeper understanding of large-scale biotechnological applications of these systems.

PROCEDURE

The instructor will decide whether the activity should be conducted individually or in pairs. Detailed methodology of this project is provided in Appendix S1, which will be shared with students 1 week prior to the scheduled project to facilitate the acquisition of necessary materials (locally or online). The experiment will be conducted in three stages, as illustrated in Fig. 1: (i) the sampling phase, which should not exceed a 2-hour session; (ii) the laboratory phase, where the MFC will be operational for 1 hour; and (iii) data interpretation, where the student will analyze the results to determine if the bacterial community is a potential biocatalyst for energy production by comparing treatment outcomes with control.

Fig 1.

Overview of application of microbial fuel cells in laboratory experimentation.

Learning goals

This experiential learning can be a single module in a Biotechnology, Environmental Science, or Microbiology class. It could also be offered as a semester-long research project or, on a larger-scale, as a course-based undergraduate research experience. By the end of this module, students will be able to (i) collect sediment samples from local ecosystems, (ii) recognize and list the main parts of a microbial fuel cell, (iii) understand the oxidation-reduction processes inside the MFC, (iv) evaluate the voltage measurements generated in the MFC to correlate results between treatments and control, and (v) suggest a possible local application of the microorganisms within interdisciplinary fields such as the research oriented toward alternative energies.

Safety issues

All work in the laboratory stage must be carried out in a biosafety level 2 area. Teachers and technicians must observe compliance with ASM BSL personal protection guidelines and requirements in the classroom. Students must use gloves for both stages: sampling and laboratory work, and additionally, they must have learned to sterilize surfaces and equipment. Students will work with unknown microorganisms, so they must have safety training to work within a laboratory and must have knowledge about the correct disposal of potentially hazardous waste.

CONCLUSION

This experiment introduces students to the principles of microbial metabolic diversity and their extensive biochemical adaptability to specific environments, such as sediments. It is a cost-effective alternative to commercial kits and integrates techniques from Microbiology and Biotechnology curricula. The proposed assay effectively demonstrates the application of environmental microorganisms as energy producers when provided with an appropriate carbon source and electron acceptor. It is recommended to store sediment aliquots in vials at −70°C for DNA extraction, which will enable detailed metagenomic and metabolomic studies for advanced Environmental Sciences courses.

SUPPLEMENTAL MATERIAL

The following material is available online at https://doi.org/10.1128/jmbe.00133-24.

Appendix S1. jmbe.00133-24-s0001.docx.

Detailed protocol.

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