Photofermentation
Photofermentation is the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group of photosynthetic bacteria by a series of biochemical reactions involving three steps similar to anaerobic conversion. Photofermentation differs from dark fermentation because it only proceeds in the presence of light.
For example, photo-fermentation with Rhodobacter sphaeroides SH2C (or many other purple non-sulfur bacteria{{cite journal | vauthors = Redwood MD, Paterson-Beedle M, Macaskie LE | title = Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy. | journal = Reviews in Environmental Science and Bio/Technology | date = June 2009 | volume = 8 | issue = 2 | pages = 149–185 | doi =10.1007/s11157-008-9144-9 | bibcode = 2009RESBT...8..149R | s2cid = 83562378 | url = http://pure-oai.bham.ac.uk/ws/files/2922596/Redwood-Patterson-Macaskie_RESTEch_2009_ePrint.pdf }}) can be employed to convert small molecular fatty acids into hydrogen{{cite journal | vauthors = Tao Y, Chen Y, Wu Y, He Y, Zhou Z | title = High hydrogen yield from a two-step process of dark-and photo-fermentation of sucrose. | journal = International Journal of Hydrogen Energy | date = February 2007 | volume = 32 | issue = 2 | pages = 200–6 | doi = 10.1016/j.ijhydene.2006.06.034 | bibcode = 2007IJHE...32..200T }} and other products.
File:General process of photofermentation - 12934 2015 324 Fig1.gif
Light-dependent pathways
= Phototropic bacteria =
Phototropic bacteria produce hydrogen gas via photofermentation, where the hydrogen is sourced from organic compounds.{{Cite journal| vauthors = Ghimire A, Frunzo L, Pirozzi F, Trably E, Escudie R, Lens PN, Esposito G |date= April 2015 |title=A review on dark fermentative biohydrogen production from organic biomass: Process parameters and use of by-products |journal=Applied Energy |volume=144 |pages=73–95 |doi=10.1016/j.apenergy.2015.01.045 |bibcode= 2015ApEn..144...73G |url= https://hal.science/hal-01164829/file/OA_Ghimire%20et%20al_reviewH2.pdf }}
= Photolytic producers =
Photolytic producers are similar to phototrophs, but source hydrogen from water molecules that are broken down as the organism interacts with light. Photolytic producers consist of algae and certain photosynthetic bacteria.
Sustainable energy production
Photofermentation via purple nonsulfur producing bacteria has been explored as a method for the production of biofuel.{{cite journal | vauthors = Corneli E, Adessi A, Olguín EJ, Ragaglini G, García-López DA, De Philippis R | title = Biotransformation of water lettuce (Pistia stratiotes) to biohydrogen by Rhodopseudomonas palustris | journal = Journal of Applied Microbiology | volume = 123 | issue = 6 | pages = 1438–1446 | date = December 2017 | pmid = 28972701 | doi = 10.1111/jam.13599 | hdl = 2434/837874 | s2cid = 4312887 | hdl-access = free }} The natural fermentation product of these bacteria, hydrogen gas, can be harnessed as a natural gas energy source.{{cite journal | vauthors = Laurinavichene T, Tekucheva D, Laurinavichius K, Tsygankov A | title = Utilization of distillery wastewater for hydrogen production in one-stage and two-stage processes involving photofermentation | journal = Enzyme and Microbial Technology | volume = 110 | pages = 1–7 | date = March 2018 | pmid = 29310850 | doi = 10.1016/j.enzmictec.2017.11.009 }}{{cite journal | vauthors = Uyar B | title = Bioreactor design for photofermentative hydrogen production | journal = Bioprocess and Biosystems Engineering | volume = 39 | issue = 9 | pages = 1331–40 | date = September 2016 | pmid = 27142376 | doi = 10.1007/s00449-016-1614-9 | s2cid = 31956368 }} Photofermentation via algae instead of bacteria is used for bioethanol production, among other liquid fuel alternatives.{{cite journal | vauthors = Costa RL, Oliveira TV, Ferreira J, Cardoso VL, Batista FR | title = Prospective technology on bioethanol production from photofermentation | journal = Bioresource Technology | volume = 181 | pages = 330–7 | date = April 2015 | pmid = 25678298 | doi = 10.1016/j.biortech.2015.01.090 | bibcode = 2015BiTec.181..330C }}
= Mechanism =
The bacteria and their energy source are held in a bioreactor chamber that is impermeable to air and oxygen free. The proper temperature for the bacterial species is maintained in the bioreactor. The bacteria are sustained with a carbohydrate diet consisting of simple saccharide molecules.{{cite journal | vauthors = Zhang Q, Wang Y, Zhang Z, Lee DJ, Zhou X, Jing Y, Ge X, Jiang D, Hu J, He C | title = Photo-fermentative hydrogen production from crop residue: A mini review | journal = Bioresource Technology | volume = 229 | pages = 222–230 | date = April 2017 | pmid = 28108074 | doi = 10.1016/j.biortech.2017.01.008 | bibcode = 2017BiTec.229..222Z }} The carbohydrates are typically sourced from agricultural or forestry waste.
= Variations =
File:Green_algae_in_a_bioreactor.jpg
In addition to wild type forms of Rhodopseudomonas palustris, scientists have used genetically modified forms to produce hydrogen as well. Other explorations include expanding the bioreactor system to hold a combination of bacteria, algae or cyanobacteria. Ethanol production is performed by the algae Chlamydomonas reinhardtii, among other species, in cycling light and dark environments. The cycling of light and dark environments has also been explored with bacteria for hydrogen production, increasing hydrogen yield.{{Cite journal| vauthors = Chen CY, Yang MH, Yeh KL, Liu CH, Chang JS |date= September 2008 |title=Biohydrogen production using sequential two-stage dark and photo fermentation processes |journal=International Journal of Hydrogen Energy|volume=33|issue=18|pages=4755–4762|doi=10.1016/j.ijhydene.2008.06.055 |bibcode= 2008IJHE...33.4755C }}
= Advantages =
The bacteria are typically fed with broken down agricultural waste or undesired crops, such as water lettuce or sugar beet molasses.{{cite journal | vauthors = Keskin T, Hallenbeck PC | title = Hydrogen production from sugar industry wastes using single-stage photofermentation | journal = Bioresource Technology | volume = 112 | pages = 131–6 | date = May 2012 | pmid = 22420990 | doi = 10.1016/j.biortech.2012.02.077 | bibcode = 2012BiTec.112..131K }} The high abundance of such waste ensures the stable food source for the bacteria and productively uses human-produced waste. In comparison with dark fermentation, photofermentation produces more hydrogen per reaction and avoids the acidic end products of dark fermentation.{{cite journal | vauthors = Chandrasekhar K, Lee YJ, Lee DW | title = Biohydrogen production: strategies to improve process efficiency through microbial routes | journal = International Journal of Molecular Sciences | volume = 16 | issue = 4 | pages = 8266–93 | date = April 2015 | pmid = 25874756 | pmc = 4425080 | doi = 10.3390/ijms16048266 | doi-access = free }}
= Limitations =
The primary limitations of photofermentation as a sustainable energy source stem from the precise requirements of maintaining the bacteria in the bioreactor. Researchers have found it difficult to maintain a constant temperature for the bacteria within the bioreactor. 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.
See also
References
{{Reflist}}
External links
{{Wiktionary|photofermentation}}
- [http://www.liebertonline.com/doi/abs/10.1089/ind.2006.2.44 Photo fermentation]
- [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 Enhancing phototropic hydrogen production by solid-carrier assisted fermentation and internal optical-fiber illumination]