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[1]) can be employed to convert small molecular fatty acids into hydrogen[2] and other products.

[3] Depicts general process of photofermentation.


Light-dependent pathways

Phototropic bacteria

Phototropic bacteria produce hydrogen gas via photofermentation, where the hydrogen is sourced from organic compounds.[4]

[4]

Photolytic producers

Photolytic 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]

(algae)[4]

(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 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 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, scientists have used genetically modified forms to produce hydrogen as well.[5] Other explorations include expanding the bioreactor system to hold a combination of bacteria, algae or cyanobacteria.[7][9] Ethanol production is performed by the algae 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, 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 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]

gollark: (also I may eventually want to use ARM)
gollark: On the one hand I do somewhat want to run osmarksforum™ with this for funlolz, but on the other hand handwritten ASM is probably not secure.
gollark: > Well, the answer is a good cause for flame war, but I will risk. ;) At first, I find assembly language much more readable than HLL languages and especially C-like languages with their weird syntax. > At second, all my tests show, that in real-life applications assembly language always gives at least 200% performance boost. The problem is not the quality of the compilers. It is because the humans write programs in assembly language very different than programs in HLL. Notice, that you can write HLL program as fast as an assembly language program, but you will end with very, very unreadable and hard for support code. In the same time, the assembly version will be pretty readable and easy for support. > The performance is especially important for server applications, because the program runs on hired hardware and you are paying for every second CPU time and every byte RAM. AsmBB for example can run on very cheap shared web hosting and still to serve hundreds of users simultaneously.
gollark: https://board.asm32.info/asmbb/asmbb-v2-9-has-been-released.328/
gollark: Huh, apparently some hugely apioformic entity wrote a bit of forum software entirely in assembly.

See also

References
  1. Redwood MD, Paterson-Beedle M, Macaskie LE (June 2009). "Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy" (PDF). Reviews in Environmental Science and Bio/Technology. 8 (2): 149–185. doi:10.1007/s11157-008-9144-9.
  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. doi:10.1016/j.ijhydene.2006.06.034.
  3. Gabrielyan, Lilit; Sargsyan, Harutyun; Trchounian, Armen (2015-09-04). "Novel properties of photofermentative biohydrogen production by purple bacteria Rhodobacter sphaeroides: effects of protonophores and inhibitors of responsible enzymes". Microbial Cell Factories. 14 (1): 131. doi:10.1186/s12934-015-0324-3. ISSN 1475-2859. PMC 4558839. PMID 26337489.
  4. 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". Applied Energy. 144: 73–95. doi:10.1016/j.apenergy.2015.01.045.
  5. 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:10.1111/jam.13599. PMID 28972701.
  6. 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:10.1016/j.enzmictec.2017.11.009. PMID 29310850.
  7. Uyar B (September 2016). "Bioreactor design for photofermentative hydrogen production". Bioprocess and Biosystems Engineering. 39 (9): 1331–40. doi:10.1007/s00449-016-1614-9. PMID 27142376.
  8. Costa RL, Oliveira TV, Ferreira J, Cardoso VL, Batista FR (April 2015). "Prospective technology on bioethanol production from photofermentation". Bioresource Technology. 181: 330–7. doi:10.1016/j.biortech.2015.01.090. PMID 25678298.
  9. 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. doi:10.1016/j.biortech.2017.01.008. PMID 28108074.
  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. doi:10.1016/j.ijhydene.2008.06.055.
  11. Keskin T, Hallenbeck PC (May 2012). "Hydrogen production from sugar industry wastes using single-stage photofermentation". Bioresource Technology. 112: 131–6. doi:10.1016/j.biortech.2012.02.077. PMID 22420990.
  12. Chandrasekhar K, Lee YJ, Lee DW (April 2015). "Biohydrogen production: strategies to improve process efficiency through microbial routes". International Journal of Molecular Sciences. 16 (4): 8266–93. doi:10.3390/ijms16048266. PMC 4425080. PMID 25874756.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.