# Photofermentation

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**Photofermentation** is the [fermentative](/source/Fermentative_hydrogen_production) conversion of organic substrate to [biohydrogen](/source/Biohydrogen) manifested by a diverse group of [photosynthetic](/source/Photosynthesis) [bacteria](/source/Bacteria) by a series of [biochemical](/source/Biochemical) reactions involving three steps similar to [anaerobic conversion](/source/Anaerobic_digestion). Photofermentation differs from [dark fermentation](/source/Dark_fermentation) because it only proceeds in the presence of [light](/source/Light).

For example, photo-fermentation with *[Rhodobacter sphaeroides](/source/Rhodobacter_sphaeroides)* SH2C (or many other purple non-sulfur bacteria[1]) can be employed to convert small molecular fatty acids into [hydrogen](/source/Hydrogen)[2] and other products.

[3] Depicts general process of photofermentation.

## Light-dependent pathways

### Phototropic bacteria

[Phototropic bacteria](/source/Phototroph) produce hydrogen gas via photofermentation, where the hydrogen is sourced from organic compounds.[4]

C 6 H 12 O 6 + 6 H 2 O → h v 6 CO 2 + 12 H 2 {\displaystyle {\ce {C6H12O6 + 6H2O ->[{hv}] 6CO2 + 12H2}}} [4]

### Photolytic producers

[Photolytic](/source/Photolysis) producers are similar to phototrophs, but source hydrogen from water molecules that are broken down as the organism interacts with light.[4] Photolytic producers consist of algae and certain photosynthetic bacteria.[4]

12 H 2 O → h v 12 H 2 + 6 O 2 {\displaystyle {\ce {12H2O ->[{hv}] 12H2 + 6O2}}} (algae)[4]

CO + H 2 O → h v H 2 + CO 2 {\displaystyle {\ce {CO + H2O ->[{hv}] H2 + CO2}}} (photolytic bacteria)[4]

## Sustainable energy production

Photofermentation via purple nonsulfur producing bacteria has been explored as a method for the production of biofuel.[5] The natural fermentation product of these bacteria, hydrogen gas, can be harnessed as a natural gas energy source.[6][7] Photofermentation via algae instead of bacteria is used for bioethanol production, among other liquid fuel alternatives.[8]

Basic principles of a bioreactor. The photofermentation bioreactor would not include an air pathway.

### Mechanism

The bacteria and their energy source are held in a [bioreactor](/source/Bioreactor) chamber that is impermeable to air and oxygen free.[7] The proper temperature for the bacterial species is maintained in the bioreactor.[7] The bacteria are sustained with a carbohydrate diet consisting of simple [saccharide](/source/Carbohydrate) molecules.[9] The carbohydrates are typically sourced from agricultural or forestry waste.[9]

### Variations

Depiction of algae (species not specified) in a bioreactor suitable for bioethanol production.

In addition to wild type forms of *[Rhodopseudomonas palustris](/source/Rhodopseudomonas_palustris), s*cientists have used [genetically modified](/source/Genetically_modified_organism) forms to produce hydrogen as well.[5] Other explorations include expanding the bioreactor system to hold a combination of bacteria, [algae](/source/Algae) or [cyanobacteria](/source/Cyanobacteria).[7][9] Ethanol production is performed by the algae *[Chlamydomonas reinhardtii](/source/Chlamydomonas_reinhardtii)*, among other species, in cycling light and dark environments.[8] The cycling of light and dark environments has also been explored with bacteria for hydrogen production, increasing hydrogen yield.[10]

### Advantages

The bacteria are typically fed with broken down agricultural waste or undesired crops, such as water lettuce or sugar beet molasses.[11][5] The high abundance of such waste ensures the stable food source for the bacteria and productively uses human-produced waste.[5] In comparison with [dark fermentation](/source/Dark_fermentation), photofermentation produces more hydrogen per reaction and avoids the acidic end products of dark fermentation.[12]

### Limitations

The primary limitations of photofermentation as a [sustainable energy](/source/Sustainable_energy) source stem from the precise requirements of maintaining the bacteria in the bioreactor.[7] Researchers have found it difficult to maintain a constant temperature for the bacteria within the bioreactor.[7] Furthermore, the growth media for the bacteria must be rotated and refreshed without introducing air to the bioreactor system, complicating the already expensive bioreactor set up.[7][9]

## See also

- [Dark fermentation](/source/Dark_fermentation)

- [Fermentative hydrogen production](/source/Fermentative_hydrogen_production)

- [Biohydrogen](/source/Biohydrogen)

- [Fermentation (biochemistry)](/source/Fermentation_(biochemistry))

- [Hydrogen production](/source/Hydrogen_production)

- [Photochemical reaction](/source/Photochemistry)

- [Photohydrogen](/source/Photohydrogen)

- [Phototroph](/source/Phototroph)

- [Photobiology](/source/Photobiology)

- [Electrohydrogenesis](/source/Electrohydrogenesis)

- [Microbial fuel cell](/source/Microbial_fuel_cell)

## References

1. **[^](#cite_ref-1)** Redwood MD, Paterson-Beedle M, Macaskie LE (June 2009). ["Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy"](http://pure-oai.bham.ac.uk/ws/files/2922596/Redwood-Patterson-Macaskie_RESTEch_2009_ePrint.pdf) (PDF). *Reviews in Environmental Science and Bio/Technology*. **8** (2): 149–185. [Bibcode](/source/Bibcode_(identifier)):[2009RESBT...8..149R](https://ui.adsabs.harvard.edu/abs/2009RESBT...8..149R). [doi](/source/Doi_(identifier)):[10.1007/s11157-008-9144-9](https://doi.org/10.1007%2Fs11157-008-9144-9). [S2CID](/source/S2CID_(identifier)) [83562378](https://api.semanticscholar.org/CorpusID:83562378).

1. **[^](#cite_ref-2)** Tao Y, Chen Y, Wu Y, He Y, Zhou Z (February 2007). "High hydrogen yield from a two-step process of dark-and photo-fermentation of sucrose". *International Journal of Hydrogen Energy*. **32** (2): 200–6. [Bibcode](/source/Bibcode_(identifier)):[2007IJHE...32..200T](https://ui.adsabs.harvard.edu/abs/2007IJHE...32..200T). [doi](/source/Doi_(identifier)):[10.1016/j.ijhydene.2006.06.034](https://doi.org/10.1016%2Fj.ijhydene.2006.06.034).

1. **[^](#cite_ref-3)** Gabrielyan, Lilit; Sargsyan, Harutyun; [Trchounian, Armen](/source/Armen_Trchounian) (2015-09-04). ["Novel properties of photofermentative biohydrogen production by purple bacteria Rhodobacter sphaeroides: effects of protonophores and inhibitors of responsible enzymes"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558839). *Microbial Cell Factories*. **14** (1): 131. [doi](/source/Doi_(identifier)):[10.1186/s12934-015-0324-3](https://doi.org/10.1186%2Fs12934-015-0324-3). [ISSN](/source/ISSN_(identifier)) [1475-2859](https://search.worldcat.org/issn/1475-2859). [PMC](/source/PMC_(identifier)) [4558839](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558839). [PMID](/source/PMID_(identifier)) [26337489](https://pubmed.ncbi.nlm.nih.gov/26337489).

1. ^ [***a***](#cite_ref-:4_4-0) [***b***](#cite_ref-:4_4-1) [***c***](#cite_ref-:4_4-2) [***d***](#cite_ref-:4_4-3) [***e***](#cite_ref-:4_4-4) [***f***](#cite_ref-:4_4-5) Ghimire A, Frunzo L, Pirozzi F, Trably E, Escudie R, Lens PN, Esposito G (April 2015). ["A review on dark fermentative biohydrogen production from organic biomass: Process parameters and use of by-products"](https://hal.science/hal-01164829/file/OA_Ghimire%20et%20al_reviewH2.pdf) (PDF). *Applied Energy*. **144**: 73–95. [Bibcode](/source/Bibcode_(identifier)):[2015ApEn..144...73G](https://ui.adsabs.harvard.edu/abs/2015ApEn..144...73G). [doi](/source/Doi_(identifier)):[10.1016/j.apenergy.2015.01.045](https://doi.org/10.1016%2Fj.apenergy.2015.01.045).

1. ^ [***a***](#cite_ref-:3_5-0) [***b***](#cite_ref-:3_5-1) [***c***](#cite_ref-:3_5-2) [***d***](#cite_ref-:3_5-3) Corneli E, Adessi A, Olguín EJ, Ragaglini G, García-López DA, De Philippis R (December 2017). "Biotransformation of water lettuce (Pistia stratiotes) to biohydrogen by Rhodopseudomonas palustris". *Journal of Applied Microbiology*. **123** (6): 1438–1446. [doi](/source/Doi_(identifier)):[10.1111/jam.13599](https://doi.org/10.1111%2Fjam.13599). [hdl](/source/Hdl_(identifier)):[2434/837874](https://hdl.handle.net/2434%2F837874). [PMID](/source/PMID_(identifier)) [28972701](https://pubmed.ncbi.nlm.nih.gov/28972701). [S2CID](/source/S2CID_(identifier)) [4312887](https://api.semanticscholar.org/CorpusID:4312887).

1. **[^](#cite_ref-:0_6-0)** Laurinavichene T, Tekucheva D, Laurinavichius K, Tsygankov A (March 2018). "Utilization of distillery wastewater for hydrogen production in one-stage and two-stage processes involving photofermentation". *Enzyme and Microbial Technology*. **110**: 1–7. [doi](/source/Doi_(identifier)):[10.1016/j.enzmictec.2017.11.009](https://doi.org/10.1016%2Fj.enzmictec.2017.11.009). [PMID](/source/PMID_(identifier)) [29310850](https://pubmed.ncbi.nlm.nih.gov/29310850).

1. ^ [***a***](#cite_ref-:1_7-0) [***b***](#cite_ref-:1_7-1) [***c***](#cite_ref-:1_7-2) [***d***](#cite_ref-:1_7-3) [***e***](#cite_ref-:1_7-4) [***f***](#cite_ref-:1_7-5) [***g***](#cite_ref-:1_7-6) Uyar B (September 2016). "Bioreactor design for photofermentative hydrogen production". *Bioprocess and Biosystems Engineering*. **39** (9): 1331–40. [doi](/source/Doi_(identifier)):[10.1007/s00449-016-1614-9](https://doi.org/10.1007%2Fs00449-016-1614-9). [PMID](/source/PMID_(identifier)) [27142376](https://pubmed.ncbi.nlm.nih.gov/27142376). [S2CID](/source/S2CID_(identifier)) [31956368](https://api.semanticscholar.org/CorpusID:31956368).

1. ^ [***a***](#cite_ref-:5_8-0) [***b***](#cite_ref-:5_8-1) Costa RL, Oliveira TV, Ferreira J, Cardoso VL, Batista FR (April 2015). "Prospective technology on bioethanol production from photofermentation". *Bioresource Technology*. **181**: 330–7. [Bibcode](/source/Bibcode_(identifier)):[2015BiTec.181..330C](https://ui.adsabs.harvard.edu/abs/2015BiTec.181..330C). [doi](/source/Doi_(identifier)):[10.1016/j.biortech.2015.01.090](https://doi.org/10.1016%2Fj.biortech.2015.01.090). [PMID](/source/PMID_(identifier)) [25678298](https://pubmed.ncbi.nlm.nih.gov/25678298).

1. ^ [***a***](#cite_ref-:2_9-0) [***b***](#cite_ref-:2_9-1) [***c***](#cite_ref-:2_9-2) [***d***](#cite_ref-:2_9-3) Zhang Q, Wang Y, Zhang Z, Lee DJ, Zhou X, Jing Y, Ge X, Jiang D, Hu J, He C (April 2017). "Photo-fermentative hydrogen production from crop residue: A mini review". *Bioresource Technology*. **229**: 222–230. [Bibcode](/source/Bibcode_(identifier)):[2017BiTec.229..222Z](https://ui.adsabs.harvard.edu/abs/2017BiTec.229..222Z). [doi](/source/Doi_(identifier)):[10.1016/j.biortech.2017.01.008](https://doi.org/10.1016%2Fj.biortech.2017.01.008). [PMID](/source/PMID_(identifier)) [28108074](https://pubmed.ncbi.nlm.nih.gov/28108074).

1. **[^](#cite_ref-10)** Chen CY, Yang MH, Yeh KL, Liu CH, Chang JS (September 2008). "Biohydrogen production using sequential two-stage dark and photo fermentation processes". *International Journal of Hydrogen Energy*. **33** (18): 4755–4762. [Bibcode](/source/Bibcode_(identifier)):[2008IJHE...33.4755C](https://ui.adsabs.harvard.edu/abs/2008IJHE...33.4755C). [doi](/source/Doi_(identifier)):[10.1016/j.ijhydene.2008.06.055](https://doi.org/10.1016%2Fj.ijhydene.2008.06.055).

1. **[^](#cite_ref-11)** Keskin T, Hallenbeck PC (May 2012). "Hydrogen production from sugar industry wastes using single-stage photofermentation". *Bioresource Technology*. **112**: 131–6. [Bibcode](/source/Bibcode_(identifier)):[2012BiTec.112..131K](https://ui.adsabs.harvard.edu/abs/2012BiTec.112..131K). [doi](/source/Doi_(identifier)):[10.1016/j.biortech.2012.02.077](https://doi.org/10.1016%2Fj.biortech.2012.02.077). [PMID](/source/PMID_(identifier)) [22420990](https://pubmed.ncbi.nlm.nih.gov/22420990).

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## External links

Look up ***[photofermentation](https://en.wiktionary.org/wiki/photofermentation)*** in Wiktionary, the free dictionary.

- [Photo fermentation](http://www.liebertonline.com/doi/abs/10.1089/ind.2006.2.44)

- [Enhancing phototropic hydrogen production by solid-carrier assisted fermentation and internal optical-fiber illumination](https://archive.today/20130202040922/http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THB-4K4WMXF-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_version=1&_urlVersion=0&_userid=10&md5=4000b749160c23c893dd4d1e1410d6cf)

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Adapted from the Wikipedia article [Photofermentation](https://en.wikipedia.org/wiki/Photofermentation) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Photofermentation?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.