SCOBY

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A SCOBY used for brewing kombucha. SCOBY mushroom.jpg
A SCOBY used for brewing kombucha.
Kombucha co-culture with SCOBY biofilm Kombucha Mature.jpg
Kombucha co-culture with SCOBY biofilm

Symbiotic culture of bacteria and yeast (SCOBY) is a culinary symbiotic fermentation culture (starter) consisting of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast which arises in the preparation of sour foods and beverages such as kombucha. [1] Beer and wine also undergo fermentation with yeast, but the lactic acid bacteria and acetic acid bacteria components unique to SCOBY are usually viewed as a source of spoilage rather than a desired addition. [2] [3] Both LAB and AAB enter on the surface of barley and malt in beer fermentation and grapes in wine fermentation; LAB lowers the pH of the beer/wine while AAB takes the ethanol produced from the yeast and oxidizes it further into vinegar, resulting in a sour taste and smell. [2] [3] AAB are also responsible for the formation of the cellulose SCOBY. [1]

Contents

In its most common form, SCOBY is a gelatinous, cellulose-based biofilm or microbial mat found floating at the container's air-liquid interface. This bacterial cellulose mat is sometimes called a pellicle. [4] SCOBY pellicles, like sourdough starters, can serve the purpose of continuing the fermentation process into a new vessel and reproducing the desired product. [4] This can be attributed to SCOBY's ability to house not only the symbiotic growth, but a small amount of the previous media and product due to its ability to absorb water. [1] SCOBYs can vary greatly in cell density within the biofilm due to fermentation conditions, leading to possible variations in the end product; numerous studies are currently taking place to determine the optimal ratio of SCOBY, if any, to liquid culture to ensure highest product consistency, as there are no standard operating procedures in place. [4] Further information such as the organisms and culture conditions necessary to ferment and form a SCOBY, biofilm characteristics, and applications in foods and beverages with specific emphasis in kombucha can be found below. [5]

Co-culture composition and conditions

Based on the desired product of the SCOBY, different species of bacteria and yeast are used. Such cultures generally include aerobic, gram negative AAB species such as Acetobacter , Gluconobacter and Komagataeibacter , aerobic, gram positive LAB such as Lactobacillus , as well as various yeasts such as Saccharomyces and Zygosaccharomyces . [1] [2] Strains are pre-screened for viability under compatible conditions, increased yield of desired product, and indisposition to compete; once chosen, various culture conditions are modified for optimal growth and productivity. [6]

For kombucha SCOBYs, the first step is yeast fermentation of sugars such as glucose from black or green tea into ethanol and carbon dioxide. [7] Zygosaccharomyces is reported to be involved in 84.1% of all kombucha SCOBY fermentation processes due to its improved stability in high sugar and halophilic conditions, while Saccharomyces is predominantly used for its efficient fermentation rates and resistance to high temperature and alcohol content. [1] Different variations of yeast can also be added as either a supplemental means to introduce different flavors and aromas or ensure reaction completion by utilizing different niches. [1] While these niches vary yeast to yeast, certain fermentation conditions remain consistent. Such conditions include but are not limited to high substrate concentration, sufficient oxygen levels, temperatures between 20 °C and 30 °C, and a pH between 4-4.5. [8]

The second step in the formation of SCOBY is the introduction of different bacteria into the liquid culture to convert the ethanol product of fermentation into organic acids such as lactic acid or acetic acid. These processes are known as lactic acid fermentation and ethanol metabolism respectively. [7] A possible byproduct of this reaction is cellulose, which serves as the foundation for the SCOBY biofilm. [4] Like yeasts, the species of bacteria chosen as well as culture conditions directly affect both the characteristics of the liquid kombucha product as well as the composition and morphology of the SCOBY pellicle. While there are many species that have the mechanisms necessary to form cellulose such as Acetobacter and Komagataeibacter, Gluconaceobacter are one of the most populous used, residing in between 86 and 99% of both liquid and biofilm cultures. [1] The necessary culturing conditions of these bacteria are similar to that of yeasts, but require more oxygen due to their aerobic nature in oxidizing ethanol to form organic acids. [9]

Once the internal conditions of the co-culture are in place, the symbiotic mixture is left to ferment. Certain studies have claimed optimal fermentation time to be 10 days, but the duration can be modified to change the contents of the yield; greater fermentation times correlate with higher levels of organic acids and other amino acids, which can attribute to the sour undertones of some Kombucha. [9] Despite controls in place, the species comprising the mixed cultures can still initiate metabolic change preparation to preparation with the slightest change in co-culture conditions and alter product qualities such as sugar concentration, so adequate monitoring is necessary when running in a continuous mode or reusing a starter culture. [1]

Biofilm characteristics

The formation of the cellulose pellicle at the surface of the broth yields a product with unique characteristics that both bacteria and consumers find advantageous. Upon inoculation into the culture, bacteria such as Acetobacter immediately begin pulling glucose molecules together outside of the cell and joining them via β(1-4) linkages to form long, slender structures extending from their cell membranes called fibrils. [1] The nanocellulose composing these fibrils demonstrates great strength and stability while still allowing hydrophilic interactions and biocompatibility, making it a great resource for the culture to use. [10] A variety of inter and intramolecular bonding events join numerous fibrils together into the final, much larger structures known as microfibrils; because of the integrity of the microfibrils and the organized, linear nature of cellulose bonds, the resulting biofilm can also be referred to as a matrix or mat. [10] This biofilm is a natural defense mechanism for the co-culture, and can withstand extreme conditions such as temperature and UV radiation. [10] Two additional characteristics of the nanofibril cellulose SCOBY—its high purity and crystallinity—are currently a target in biomedical research in the formation of biocompatible tissue scaffolds, cardiovascular components such as blood vessels, bone grafts, and connective tissue replacements. [11] The nanocellulose fibrils can also be extracted via acid hydrolysis and used in the food packaging, clothing, and wastewater treatment industries. [1] [10]

The thickness of a kombucha SCOBY is contingent on all brewing conditions, but one study reported an average a thickness of two to five millimeters. [12] SCOBYs can be divided to start multiple cultures or dehydrated for storage and later use. Once removed, the culture will begin to regenerate a new pellicle known informally as a "baby SCOBY." This process can be repeated multiple times for months at a time. [13]

A group of kombucha SCOBYs Kombucha scobies.jpg
A group of kombucha SCOBYs

Use in food production

In addition to kombucha, there are a variety of other foods and beverages which require a similar "symbiotic culture" in their production such as:

Use in clothing production

Queensland University of Technology and the State Library of Queensland have been using kombucha scoby to produce a workable bio-textile, called a "vegan leather". [14]

Use in circuit boards

A small international team of material and computer engineers from the UK, Italy and Greece has tested the possibility of using kombucha SCOBY to produce electronic circuit boards. [15]

See also

Related Research Articles

Acetic acid bacteria (AAB) are a group of Gram-negative bacteria which oxidize sugars or ethanol and produce acetic acid during fermentation. The acetic acid bacteria consist of 10 genera in the family Acetobacteraceae. Several species of acetic acid bacteria are used in industry for production of certain foods and chemicals.

<span class="mw-page-title-main">Mother of vinegar</span> Biofilm formed on fermenting alcoholic liquids

Mother of vinegar is a biofilm composed of a form of cellulose, yeast, and bacteria that sometimes develops on fermenting alcoholic liquids during the process that turns alcohol into acetic acid with the help of oxygen from the air and acetic acid bacteria (AAB). It is similar to the symbiotic culture of bacteria and yeast (SCOBY) mostly known from production of kombucha, but develops to a much lesser extent due to lesser availability of yeast, which is often no longer present in wine/cider at this stage, and a different population of bacteria. Mother of vinegar is often added to wine, cider, or other alcoholic liquids to produce vinegar at home, although only the bacteria is required, but historically has also been used in large scale production.

<span class="mw-page-title-main">Sourdough</span> Type of sour bread

Sourdough or sourdough bread is a bread made by the fermentation of dough using wild lactobacillaceae and yeast. Lactic acid from fermentation imparts a sour taste and improves keeping qualities.

<span class="mw-page-title-main">Kombucha</span> Fermented tea beverage

Kombucha is a fermented, lightly effervescent, sweetened black tea drink. Sometimes the beverage is called kombucha tea to distinguish it from the culture of bacteria and yeast. Juice, spices, fruit or other flavorings are often added.

<span class="mw-page-title-main">Winemaking</span> Production of wine

Winemaking, wine-making, or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. There is evidence that suggests that the earliest wine production took place in Georgia and Iran around 6000 to 5000 B.C. The science of wine and winemaking is known as oenology. A winemaker may also be called a vintner. The growing of grapes is viticulture and there are many varieties of grapes.

<span class="mw-page-title-main">Malolactic fermentation</span> Process in winemaking

Malolactic conversion is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.

Industrial fermentation is the intentional use of fermentation in manufacturing processes. In addition to the mass production of fermented foods and drinks, industrial fermentation has widespread applications in chemical industry. Commodity chemicals, such as acetic acid, citric acid, and ethanol are made by fermentation. Moreover, nearly all commercially produced industrial enzymes, such as lipase, invertase and rennet, are made by fermentation with genetically modified microbes. In some cases, production of biomass itself is the objective, as is the case for single-cell proteins, baker's yeast, and starter cultures for lactic acid bacteria used in cheesemaking.

A wine fault is a sensory-associated (organoleptic) characteristic of a wine that is unpleasant, and may include elements of taste, smell, or appearance, elements that may arise from a "chemical or a microbial origin", where particular sensory experiences might arise from more than one wine fault. Wine faults may result from poor winemaking practices or storage conditions that lead to wine spoilage.

<span class="mw-page-title-main">Tibicos</span> Fermented drink

Tibicos, or water kefir, is a traditional fermented drink made with water and a water kefir grains held in a polysaccharide biofilm matrix created by the bacteria. It is sometimes consumed as an alternative to milk-based probiotic drinks or tea-cultured products such as kombucha. Water kefir is typically made as a probiotic homebrew beverage. The finished product, if bottled, will produce a carbonated beverage.

<span class="mw-page-title-main">Apple cider vinegar</span> Vinegar made from fermented apple juice

Apple cider vinegar, or cider vinegar, is a vinegar made from cider, and used in salad dressings, marinades, vinaigrettes, food preservatives, and chutneys. It is made by crushing apples, then squeezing out the juice. The apple juice is then fermented by yeast which converts the sugars in the juice to ethanol. In a second fermentation step, the ethanol is converted into acetic acid by acetic acid-forming bacteria, yielding cider vinegar. Acetic acid and malic acid combine to give this vinegar its sour taste.

<span class="mw-page-title-main">Bioconversion of biomass to mixed alcohol fuels</span>

The bioconversion of biomass to mixed alcohol fuels can be accomplished using the MixAlco process. Through bioconversion of biomass to a mixed alcohol fuel, more energy from the biomass will end up as liquid fuels than in converting biomass to ethanol by yeast fermentation.

<span class="mw-page-title-main">Fermentation in food processing</span> Converting carbohydrates to alcohol or acids using anaerobic microorganisms

In food processing, fermentation is the conversion of carbohydrates to alcohol or organic acids using microorganisms—yeasts or bacteria—under anaerobic (oxygen-free) conditions. Fermentation usually implies that the action of microorganisms is desired. The science of fermentation is known as zymology or zymurgy.

<span class="mw-page-title-main">Food microbiology</span> Study of the microorganisms that inhibit, create, or contaminate food

Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. This includes the study of microorganisms causing food spoilage; pathogens that may cause disease ; microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing probiotics.

<span class="mw-page-title-main">Kefir</span> Fermented milk drink made from kefir grains

Kefir is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. It is prepared by inoculating the milk of cows, goats, or sheep with kefir grains.

<span class="mw-page-title-main">Bacterial cellulose</span> Organic compound

Bacterial cellulose is an organic compound with the formula (C
6H
10O
5)
n produced by certain types of bacteria. While cellulose is a basic structural material of most plants, it is also produced by bacteria, principally of the genera Komagataeibacter, Acetobacter, Sarcina ventriculi and Agrobacterium. Bacterial, or microbial, cellulose has different properties from plant cellulose and is characterized by high purity, strength, moldability and increased water holding ability. In natural habitats, the majority of bacteria synthesize extracellular polysaccharides, such as cellulose, which form protective envelopes around the cells. While bacterial cellulose is produced in nature, many methods are currently being investigated to enhance cellulose growth from cultures in laboratories as a large-scale process. By controlling synthesis methods, the resulting microbial cellulose can be tailored to have specific desirable properties. For example, attention has been given to the bacteria Komagataeibacter xylinus due to its cellulose's unique mechanical properties and applications to biotechnology, microbiology, and materials science.

A pellicle is a skin or coating of proteins or cellulose on the surface of meat or fermented beverages.

<i>Acetobacter aceti</i> Species of bacterium

Acetobacter aceti, a Gram-negative bacterium that moves using its peritrichous flagella, was discovered when Louis Pasteur proved it to be the cause of conversion of ethanol to acetic acid in 1864. Today, A.aceti is recognized as a species within the genus Acetobacter, belonging to the family Acetobacteraceae in the class Alphaproteobacteria. Its bacterial motility plays an important role in the formation of biofilms, intricate communities where A. aceti cells aggregate and collaborate, further enhancing their ability to metabolize ethanol and produce acetic acid. Widely distributed in various environmental niches, this benign microorganism thrives in habitats abundant in fermentable sugars, such as flowers, fruits, honey, water, and soil, present wherever sugar fermentation occurs. A. aceti grows best within temperatures ranging from 25 to 30 degrees Celsius, with an upper limit of 35 degrees Celsius, and in slightly acidic conditions with a pH between 5.5 to 6.3. A. aceti has long been used in the fermentation industry efficiently producing acetic acid from alcohol as an obligate aerobe dependent on oxygen as the terminal electron acceptor. A. aceti, classified as an acidophile, able to survive in acidic environments, possesses an acidified cytoplasm, providing most proteins with acid stability. The microorganism's ability to thrive in environments rich in fermentable sugars shows its potential as an organism for studying microbial metabolism and adaptation.

Symbiotic fermentation is a form of fermentation in which multiple organisms interact in symbiosis in order to produce the desired product. For example, a yeast may produce ethanol, which is then consumed by an acetic acid bacterium. Described early on as the fermentation of sugars following saccharification in a mixed fermentation process.

Jun, or Xun, is a fermented drink similar to kombucha, differing only in that its base ingredients are green tea and honey instead of black tea and cane sugar. Jun is brewed by fermenting green tea with a symbiotic culture of bacteria and yeast (SCOBY). Fruits, sweeteners, spices, and other flavor enhancers are also commonly added to make the taste of the beverage more appealing. Though Jun bears similarities to other fermented drinks like kombucha, water kefir, and kvass, it has enough differences to be considered a distinct drink.

Komagataeibacter xylinus is a species of bacteria best known for its ability to produce cellulose, specifically bacterial cellulose.

References

  1. 1 2 3 4 5 6 7 8 9 10 Villarreal-Soto, Silvia Alejandra; Beaufort, Sandra; Bouajila, Jalloul; Souchard, Jean-Pierre; Taillandier, Patricia (March 2018). "Understanding Kombucha Tea Fermentation: A Review: Understanding Kombucha tea fermentation…". Journal of Food Science. 83 (3): 580–588. doi: 10.1111/1750-3841.14068 . PMID   29508944.
  2. 1 2 3 Bokulich, N. A.; Bamforth, C. W. (2013-06-01). "The Microbiology of Malting and Brewing". Microbiology and Molecular Biology Reviews. 77 (2): 157–172. doi:10.1128/MMBR.00060-12. ISSN   1092-2172. PMC   3668669 . PMID   23699253.
  3. 1 2 "Lactic Acid Bacteria and Wine Spoilage". Midwest Grape and Wine Industry Institute. Retrieved 2020-05-12.
  4. 1 2 3 4 May, Alexander; Narayanan, Shrinath; Alcock, Joe; Varsani, Arvind; Maley, Carlo; Aktipis, Athena (2019-09-03). "Kombucha: a novel model system for cooperation and conflict in a complex multi-species microbial ecosystem". PeerJ. 7: e7565. doi: 10.7717/peerj.7565 . ISSN   2167-8359. PMC   6730531 . PMID   31534844.
  5. ↑ "Homemade Kombucha". Fonsly. 13 November 2019. Retrieved 1 August 2021.
  6. ↑ Yao, Wanying; Nokes, Sue E. (2013). "The use of co-culturing in solid substrate cultivation and possible solutions to scientific challenges". Biofuels, Bioproducts and Biorefining. 7 (4): 361–372. doi:10.1002/bbb.1389. ISSN   1932-1031. S2CID   55738159.
  7. 1 2 "Experiment with Fermentation using Kombucha". RockEDU. Retrieved 2020-05-12.
  8. ↑ "Fermented and vegetables. A global perspective. Chapter 3". www.fao.org. Retrieved 2020-05-12.
  9. 1 2 St-Pierre, Danielle (2019-08-23). Microbial Diversity of the Symbiotic Colony of Bacteria and Yeast (SCOBY) and its Impact on the Organoleptic Properties of Kombucha (MS thesis). The University of Maine.
  10. 1 2 3 4 Dima, Stefan-Ovidiu; Panaitescu, Denis-Mihaela; Orban, Csongor; Ghiurea, Marius; Doncea, Sanda-Maria; Fierascu, Radu Claudiu; Nistor, Cristina Lavinia; Alexandrescu, Elvira; Nicolae, Cristian-Andi; Trică, Bogdan; Moraru, Angela (2018). "Bacterial Nanocellulose from Side-Streams of Kombucha Beverages Production: Preparation and Physical-Chemical Properties". Polymers. 9 (8): 374. doi: 10.3390/polym9080374 . PMC   6418918 . PMID   30971046.
  11. ↑ Torres, Fernando; Commeaux, Solene; Troncoso, Omar (2012-12-05). "Biocompatibility of Bacterial Cellulose Based Biomaterials". Journal of Functional Biomaterials. 3 (4): 864–878. doi: 10.3390/jfb3040864 . ISSN   2079-4983. PMC   4030925 . PMID   24955750.
  12. ↑ Shade, Ashley (2011-07-27). "The Kombucha Biofilm: a Model System for Microbial Ecology" (PDF). Yale University. Archived from the original (PDF) on 2021-02-17. Retrieved 2020-05-12.
  13. ↑ "The 30+ Most Common Questions About Kombucha Tea | Kombucha FAQ" . Retrieved 2020-05-12.
  14. ↑ Mitchell-Whittington, Amy (2016-08-04). "QUT and State Library leading the way in 'vegan leather'". BrisbaneTimes.com.au. Retrieved 2016-08-05.
  15. ↑ Yirka, Bob; Xplore, Tech. "Testing the use of kombucha to make circuit boards". techxplore.com. Retrieved 2023-05-24.

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