# Towards Bio-Hybrid Energy Harvesting in the Real-World:
## 3 Research Progress in Energy Harvesting from Microorganisms
### Impact of Other Micro and Macro Organisms in MFCs
#### 3.3.2 Yeast-Aided MFCs  
Fungi are considered the second most commonly used microorganism for MFCs. [PERSON] et al. [157] reported his work where _Saccharomyces cerevisiae_ was tested as MFC biocatalyst and their performance in the MFC setup was tested without any mediator and in three different pH conditions. The test results indicated that _Saccharomyces cerevisiae_ can be used as an effective anodic biocatalyst for MFC setups. In a similar work [166] a cubic MFC reactor was fabricated with _Saccharomyces cerevisiae_ PTCC 5269 as active biocatalyst with neutral red and potassium permanganate as mediators in anode and cathode compartments. [PERSON] et al. [46] concentrated their focus on the _Candidia melibiosica_ 2491 yeast strain and found that it could be used as anodic biocatalyst even without any artificial mediators. [PERSON] et al. [167] reported that _Saccharomyces cerevisiae_ can perform as an effective biocatalyst of MFC in the presence of thionine. [PERSON] et al. [168] provided a review on extracellular based bio-matrices where it summarizes the top-notch yeast-based biofuel cell research and developments.  
For more details on current state-of-the-art MFC systems that utilize fungi for biocatalysts please refer to the works of [PERSON] and [PERSON] [169]. [PERSON] et al. [170] reported their primary experimental evidence that fungi isolated from the Caatinga region in Brazil can be used as efficient biocatalysts for MFCs. For their study they tested three Brazilian filamentous fungi _Rhizopus_ sp. (SIS-31), _Apergillus_ sp. (SIS-18) and _Penicillium_ sp. (SIS-21) and proved all three of them were compatible for MFC air-cathode configuration. [PERSON] et al. [171] reported examining MFC power-generation performance for seven different kinds of yeast. Their performances were evaluated with a milliliter scale, dual-chamber MFC cell configuration where carbon fiber bundles were used as electrodes. They utilized a combination of glucose and xylose for substrate, which was extracted from wood biomass. They found _Kluyveromyces marxianus_ to be a good candidate for biocatalytic activity and this finding can be particularly advantageous for power extraction from woody biomass. [PERSON] et al. [172] reported use of yeast-based MFC system with mediator methylene blue and electron acceptor K\({}_{3}\)Fe(CN)\({}_{6}\). Impact of two inorganic mediators, methylene blue and methyl red were tested on a fungi-MFC and was reported by [PERSON] et al. [103]. The authors found that yeast _Saccharomyces cerevisiae_ performs better with methylene blue. [PERSON] et al. [173] reported a fungus _Sedosporium dehoogii_ in a MFC that can decompose acetaminophen, a widely used component in pharmaceutical industries whose degradation is quite difficult. Along with decomposing acetaminophen, the fungal MFC also provided a stable power output of 50 mW/m\({}^{2}\).  
In addition to only bacteria and only fungi-based configurations, it has been proven that catalytic activities of bacteria in MFC can be boosted with addition of fungi. For example, [PERSON] et al. [174] reported developing a combined fungus-bacterium MFC. The authors grew fungus _Trametes versicolor_ with _Shevanella oneidensis_ in such a way that the bacterium could use the fungus network for efficient electron transport towards the anode. Work has also been undertaken on investigating the impacts of mutual interaction of bacteria and yeasts in MFCs and the results seem very promising. For example, [PERSON] et al. [175] found that electron shuttle-generating bacteria _Klebsiella pneumonia_ boosted the performance of yeast _Lipomyces starkeyi_ based MFCs.