Industrial fermentation

Source: Wikipedia, the free encyclopedia.

Industrial fermentation is the intentional use of

starter cultures for lactic acid bacteria used in cheesemaking
.

In general, fermentations can be divided into four types:[2]

  • Production of biomass (viable cellular material)
  • Production of extracellular metabolites (chemical compounds)
  • Production of intracellular components (enzymes and other proteins)
  • Transformation of substrate (in which the transformed substrate is itself the product)

These types are not necessarily disjoined from each other, but provide a framework for understanding the differences in approach. The organisms used are typically

dilute solution
.

General process overview

In most industrial fermentations, the organisms or

eukaryotic cells are submerged in a liquid medium; in others, such as the fermentation of cocoa beans, coffee cherries, and miso, fermentation takes place on the moist surface of the medium.[5][6]

There are also industrial considerations related to the fermentation process. For instance, to avoid biological process contamination, the fermentation medium, air, and equipment are sterilized. Foam control can be achieved by either mechanical foam destruction or chemical

industrial scale equipment. Although many parameters have been tested for use as scale up criteria, there is no general formula because of the variation in fermentation processes. The most important methods are the maintenance of constant power consumption per unit of broth and the maintenance of constant volumetric transfer rate.[3]

Phases of growth

Bacterial growth curve

Fermentation begins once the growth medium is inoculated with the organism of interest. Growth of the inoculum does not occur immediately. This is the period of adaptation, called the lag phase.[7] Following the lag phase, the rate of growth of the organism steadily increases, for a certain period—this period is the log or exponential phase.[7]

After a phase of exponential growth, the rate of growth slows down, due to the continuously falling concentrations of nutrients and/or a continuously increasing (accumulating) concentrations of toxic substances. This phase, where the increase of the rate of growth is checked, is the deceleration phase. After the deceleration phase, growth ceases and the culture enters a stationary phase or a steady state. The biomass remains constant, except when certain accumulated chemicals in the culture chemically break down the cells in a process called

chemolysis. Unless other microorganisms contaminate the culture, the chemical constitution remains unchanged. If all of the nutrients in the medium are consumed, or if the concentration of toxins is too great, the cells may become senescent and begin to die off. The total amount of biomass may not decrease, but the number of viable organisms will decrease.[citation needed
]

Fermentation medium

The microbes or eukaryotic cells used for fermentation grow in (or on) specially designed growth medium which supplies the nutrients required by the organisms or cells. A variety of media exist, but invariably contain a carbon source, a nitrogen source, water, salts, and micronutrients. In the production of wine, the medium is grape must. In the production of bio-ethanol, the medium may consist mostly of whatever inexpensive carbon source is available.[citation needed]

Carbon sources are typically sugars or other carbohydrates, although in the case of substrate transformations (such as the production of vinegar) the carbon source may be an alcohol or something else altogether. For large scale fermentations, such as those used for the production of ethanol, inexpensive sources of carbohydrates, such as

beta galactosidase, invertase or other amylases may be fed starch to select for organisms that express the enzymes in large quantity.[citation needed
]

phospholipids in cellular membranes and for the production of nucleic acids. The amount of phosphate which must be added depends upon the composition of the broth and the needs of the organism, as well as the objective of the fermentation. For instance, some cultures will not produce secondary metabolites in the presence of phosphate.[9]

Growth factors and trace nutrients are included in the fermentation broth for organisms incapable of producing all of the vitamins they require.

chelating agent may be necessary.[citation needed
]

Developing an optimal medium for fermentation is a key concept to efficient optimization. One-factor-at-a-time (OFAT) is the preferential choice that researchers use for designing a medium composition. This method involves changing only one factor at a time while keeping the other concentrations constant. This method can be separated into some sub groups. One is Removal Experiments. In this experiment all the components of the medium are removed one at a time and their effects on the medium are observed. Supplementation experiments involve evaluating the effects of nitrogen and carbon supplements on production. The final experiment is a replacement experiment. This involves replacing the nitrogen and carbon sources that show an enhancement effect on the intended production. Overall OFAT is a major advantage over other optimization methods because of its simplicity.[10]

Production of biomass

E. coli, and others. In the case of single-cell protein, algae is grown in large open ponds which allow photosynthesis to occur.[11] If the biomass is to be used for inoculation of other fermentations, care must be taken to prevent mutations
from occurring.

Production of extracellular metabolites

cyclosporin A, gibberellin, and lovastatin.[9]

Primary metabolites

Primary metabolites are compounds made during the ordinary metabolism of the organism during the growth phase. A common example is ethanol or lactic acid, produced during glycolysis. Citric acid is produced by some strains of Aspergillus niger as part of the citric acid cycle to acidify their environment and prevent competitors from taking over. Glutamate is produced by some Micrococcus species,[12] and some Corynebacterium species produce lysine, threonine, tryptophan and other amino acids. All of these compounds are produced during the normal "business" of the cell and released into the environment. There is therefore no need to rupture the cells for product recovery.

Secondary metabolites

Secondary metabolites are compounds made in the stationary phase; penicillin, for instance, prevents the growth of bacteria which could compete with Penicillium molds for resources. Some bacteria, such as Lactobacillus species, are able to produce bacteriocins which prevent the growth of bacterial competitors as well. These compounds are of obvious value to humans wishing to prevent the growth of bacteria, either as antibiotics or as antiseptics (such as gramicidin S). Fungicides, such as griseofulvin are also produced as secondary metabolites.[9] Typically secondary metabolites are not produced in the presence of glucose or other carbon sources which would encourage growth,[9] and like primary metabolites are released into the surrounding medium without rupture of the cell membrane.

In the early days of the

E. coli; by 2004 more biopharmaceuticals were manufactured in eukaryotic cells, such as CHO cells, than in microbes, but used similar bioreactor systems.[6] Insect cell culture systems came into use in the 2000s as well.[13]

Production of intracellular components

Of primary interest among the intracellular components are microbial

lysate
to be purified.

Transformation of substrate

Substrate transformation involves the transformation of a specific compound into another, such as in the case of phenylacetylcarbinol, and steroid biotransformation, or the transformation of a raw material into a finished product, in the case of food fermentations and sewage treatment.

Food fermentation

Main article: Fermentation in food processing

In the

curds, idli, dosa, etc., can be dated to more than seven thousand years ago.[15] They were developed long before humanity had any knowledge of the existence of the microorganisms involved. Some foods such as Marmite are the byproduct of the fermentation process, in this case in the production of beer
.

Ethanol fuel

Fermentation is the main source[

sugar cane, potato, cassava, and maize
are fermented by yeast to produce ethanol which is further processed to become fuel.

Sewage treatment

In the process of

electrical generators
. One advantage of bacterial digestion is that it reduces the bulk and odor of sewage, thus reducing space needed for dumping. The main disadvantage of bacterial digestion in sewage disposal is that it is a very slow process.

Agricultural feed

A wide variety of

cellulosic wastes to increase protein content and improve in vitro digestibility.[16]

Precision fermentation

Precision fermentation is an approach to manufacturing specific functional products which intends to minimise the production of unwanted by-products through the application of synthetic biology, particularly by generating synthetic "cell factories" with engineered genomes and metabolic pathways optimised to produce the desired compounds as efficiently as possible with the available resources.[17] Precision fermentation of genetically modified microorganisms may be used to manufacture proteins needed for cell culture media,[18] providing for serum-free cell culture media in the manufacturing process of cultured meat.[19] A 2021 publication showed that photovoltaic-driven microbial protein production could use 10 times less land for an equivalent amount of protein compared to soybean cultivation.[20]

See also

References

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  2. ISBN 978-0750645010
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  3. ^ a b "Fermentation". Rpi.edu. Archived from the original on 2015-06-15. Retrieved 2015-06-02.
  4. ISBN 9780070151383
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  5. ^ "Fermentation (Industrial)" (PDF). Massey.ac.nz. Retrieved 2015-06-02.
  6. ^
    S2CID 20428452
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  7. ^ a b "Bacterial Growth". Bacanova. Archived from the original on 29 October 2013.
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  9. ^
    ISBN 978-1-84755-149-8. Archived from the original
    (PDF) on 2012-12-02.
  10. PMID 28111566
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  11. ^ "Algae harvesting – Industrial fermentation – Separators". Alfalaval.com. Archived from the original on 2015-06-02. Retrieved 2015-06-02.
  12. PMID 15965888
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  13. PMID 21983546
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  14. ISBN 978-1-466-59454-8
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  15. ISBN 978-94-011-7693-4. {{cite book}}: |journal= ignored (help
    )
  16. hdl:1807/48850
    . Retrieved 2015-06-02.
  17. PMID 33908143
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  18. OCLC 1257489312
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  19. S2CID 245491693
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  20. PMID 34155098
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Bibliography

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