Other Reduced End Products

Microbial electro synthesis/bioelectrosynthesis is the process of production of chemical compounds through a series of microbially or enzymatically catalyzed reactions in a specially designed electrochemical cell called bioelectrochemical system (BES). Microbially catalyzed synthesis of organic or inorganic compounds in an electrochemical cell where the electricity driven reduction or oxidation of diverse feed stocks. Interaction between biocatalysts and solid electron acceptors (electrodes) forms the basis for microbial electrosynthesis (Rabaey and Rozendal

2010) . After H2, the reduction of CO2 to reduced end products is other rapidly growing technology (Rabaey and Rozendal 2010). CO2 in combination with the H2 and CO (syngas) can be reduced to different products, viz., acetate, ethanol, butanol, etc. However, the conversion is based on the applied potential and the efficiency is based on the gas composition (Rabaey and Rozendal 2010). The disadvantage in CO2 reduction to organic compounds by considering it as electron acceptor is the requirement of higher number of electrons. For example, the reduction of butyrate to butanol requires only four electrons, while the reduction of CO2 to butanol requires 24 electrons accounting for higher power requirement for this reaction to happen. However, CO2 availability is ubiquitous and it is good electron acceptor. Anyhow, its removal from the atmosphere is necessary in the environmental concern to remove carbon footprints (Rabaey and Rozendal 2010). With the aid of small input of electric power, many value-added compounds were formed at the cathode and the major achievements are as follows., the yield of glutamic acid was increased during glucose fermentation (Hongo and Iwahara 1979), yield of butanol was increased during Clostridium acetobutylicum fer­mentation (Kim and Kim 1988), neutral red when electrically reduced serves as the sole electron donor for the growth of Actinobacillus succinogenes and for methane production by using mixed population (Park et al. 1999), Acetate formation was shifted to propionate by mediated current supply during glucose fermentation,

Electron donor


MEC configuration

Hydrogen yield



Enriched anode respiring bacteria from MFC

Single chamber; membraneless

4.3 m3H2/m3/day

Lee and Rittmann (2010)

Anaerobic sludge

Double chamber; with PEM

1.12 mol Ho

Sun et al. (2008)

Acetic acid fed MFC bacteria

Multi electrode MEC

0.53 m3Ho/m3/day

Rader and Logan (2010)

Shewanella oneiclensis

Single chamber; membrane less

0.69 m3Ho/m3/day

Hu et al. (2008)

Geobacter sulfurreducens

Single chamber; membrane less

1.9 m3H2/m3/day

Call et al. (2009)

Geobacter metallireducens

Single chamber; membrane less

1.3-0.1 m3

Call et al. (2009)

Clostridium thermocellum 27,405

Single chamber; cylindrical MEC

Acetic acid-1,400 ml Ho/g COD

Lalaurette et al. (2009)

Succinic acid

Clostridium thermocellum 27,405

Single chamber; cylindrical MEC

1,100-130 ml Ho/g COD

Lalaurette et al. (2009)

Formic acid

Clostridium thermocellum 27,405

Single chamber; cylindrical MEC

810-260 ml-Ho/g COD

Lalaurette et al. (2009)


Heat treated anaerobic sludge

Single chamber; membrane less

5.39 mmol Ho

Escapa et al. (2009)

Microbial nutrient medium

Mixed culture

Two identical electrochemical cells operated in continuous mode

0.63 m3Ho/m3/day

Jeremiasse et al. (2010)

Swine wastewater

Exoelectrogenic bacteria

Single chamber; membrane less

0.9-1.0 m3Ho/m3/day

Wagner et al. (2009)

Bovine serum

Exoelectrogenic bacteria

Single chamber; membrane less

21.0 ± 5.0 mmol Ho/g COD

Lu et al. (2010)


Winery wastewater

Exoelectrogenic bacteria

Single chamber; membrane less

0.17-0.01 m3Ho/m3/day

Cusick et al. (2010)

Domestic waste

Exoelectrogenic bacteria

Single chamber; membrane less

0.28-0.04 m3Ho/m3/day

Cusick et al. (2010)


Municipal solid waste

Endogenous bacteria of municipal solid waste

Single chamber; membrane less

0.035 m3Ho/m3/day

Dictor et al. (2010)

Designed synthetic wastewater

Anaerobic mixed consortia

Single chamber; membrane less

8.42 mol Но/Kg CODR-day

Venkata Mohan and Lenin Babu (2011)


Sewage sludge

Double chamber MEC

35 ml Ho

Cheng et al. (2010)


Table 14.4 Different electron donors used during MEC operation along with the respective biocatalysts and hydrogen yields

14 Microbial Fuel Cells 357

By applying mediated current to the microbial population enhances acetate consumption and ethanol production (Steinbusch et al. 2010), DET from cathode to Geobacter species is established where the biofilm attached involves in the reduction of the fumerate to succinate (Gregory et al. 2004).

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