All living organisms, including the various bacteria and yeasts in the Kombucha culture, require a number of basic building blocks, nutrients and growth factors to be able to thrive. Most of them are absolutely essential and without them life would not be possible. Following is an overview:
The four basic building blocks
These four elements represent 96.5% of all living matter in the world. If only one of them was missing there would be no life on earth as we know it. In bacteria and yeasts these percentages are somewhat different. For examples, nitrogen constitutes about 10% of the dry weight of bacteria.
Oxygen, carbon and hydrogen are found in practically all organic compounds. For example, glucose, a simple sugar which is the direct energy source for Kombucha, consists of only these three elements. It has the formula C6H12O6. One molecule of glucose consists of six carbon atoms, twelve hydrogen atoms and six oxygen atoms. It is actually arranged in a three-dimensional ring shape. (Two-dimensional ring representation)
Nitrogen is one of the major constituents of DNA making up the famous strands of the double helix. DNA carries the blue-print of life and is found in every cell. Without the information encoded as nucleotide sequences, perhaps comparable to a computer program, no enzymes, no cell walls, no energy carriers could be produced, no cell could divide, no new generations would be born.
Other critical building blocks
Some of these are needed as cofactors in essential enzymes, others are used in other important compounds. For example, phosphorus is needed for cell walls, DNA and in the energy carrier ATP and so on.
There are additional elements not listed here which are considered minor but most of them nevertheless needed.
A number of bacteria and yeasts are not able to synthesize these growth factors themselves and have to rely on others to provide them. For example, lactic acid bacteria have only limited synthetic capabilities and practically require all of these growth factors.
Vitamins regulate reactions that occur in metabolism. They work together with enzymes in the building or break-down of other compounds.
Amino acids are the building blocks of proteins. Proteins have many different functions: energy storage, enzymes, structure, hormones, signal receptors, anti-bodies, transport.
Purines and pyrimidine based compounds are substances required as precursors for the synthesis of nucleic acids (DNA etc.).
All living cells require some sort of energy source. Plants get their energy from light sources through photosynthesis and store this energy in the form of chemical compounds. These compounds, for example starches and sugars, are in turn used as energy source by other organisms. The Kombucha yeasts and bacteria use sugar or a derivative (alcohol) to get the energy they need to exist. Energy is bound up in sugar in the form of chemical bonds. By breaking down these bonds through fermentation or respiration, this energy is converted into the universal energy carrier ATP (adenosine triphosphate) which powers all life processes in every living organism, plants and animals alike.
Composition of Bacteria Cells
In aerobic bacteria, approximately 50% of the energy from
glucose is oxydized to CO2 and H2O in the process of building the
ATP energy molecule which in turn supplies the energy needs for
cell functioning and growth. The other 50% is converted into
cellular material. If ethanol alcohol is metabolized instead of
glucose, as is the case for the acetobacter xylinum in Kombucha,
these percentages would be different. Furthermore, in a typical
anaerobic fermentation process as found in the K.T. lactic acid
bacteria and yeasts, more glucose would probably be required for
energy needs and less would be available for cellular material. A
typical bacterial cell, to give some idea of how cellular
components are distributed, consists of 52% protein and 19%
nucleic material (Gottschalk, 1979).
|Constituents||g/100g of dry weight|
Stouthammer AH. quoted in Gottschalk, 1979. Note: These figures are representative but vary markedly among different bacteria and with different growing conditions.
The Kombucha culture has the following components available:
Lets look at each one of these components in more detail:
Sugar provides all the fuel needed to keep the Kombucha culture well and alive. Although sugar does include oxygen atoms, the oxygen required for the bacterial respiration does not come from it or the water. It has to be provided as free oxygen O2 from the surrounding air. The sugar used for preparing the tea is table sugar or sucrose, a disaccharide ("di" means two). Since the sucrose molecules are too large to be able to enter the cell walls of the yeast, they must be broken down first by enzymes into its components, the simple sugars glucose and fructose. Both are monosaccharides ("mono" means one). During a recent experiment using a spectrophotometer I found a significant quantity of protein in fermented K. tea. Initially I did not have an explanation for this finding. Later I interpreted this to indicate the presence of the enzymatic proteins required to break down nutrients into sufficiently small molecules capable of entering the cells of the microorganisms. One or maybe even two different enzymes are needed to break down caffeine and theophylline (see below). Another one would be sucrase (also called sucrose alpha-glucosidase) which cleaves sucrose into the simpler sugars fructose and glucose. In an article by Reiss (1987) he describes an experiment in which glucose concentration starts to rise steeply after about 4 days to reach a maximum after 9 days (see chart). This is a clear indication that enzymes are in fact breaking down the white sugar outside of the cells. Since enzymes are not getting used up in the catalytic process they would reach a maximum after a few days and would remain in the tea even after the tea has finished with fermentation.
Water is essential for life. Kombucha bacteria and yeasts must have water to be able to metabolize the food provided, to grow and to multiply. Water usually contains trace elements which vary with location. Some of these trace elements are needed by the Kombucha culture. Distilled water does not contain any trace elements.
Unfortunately, tap water often contains contaminents as well as undesirable microorganisms. Boiling the water for a sufficient length of time will usually kill the microorganisms. It will also remove chemicals like chlorine but not other contaminents.
Many but not all microorganisms require oxygen for their metabolic processes. There are several major categories: 1. Strict anaerobs, organisms that only metabolize without oxygen. This process is called fermentation. 2. Facultative anaerobs, organisms that can either, under the absence of oxygen, ferment foods into ethanol or lactic acid or, under the presence of oxygen, metabolize (respiration) food completely into CO2 and water. 3. Strict aerobs, organisms that must have oxygen to be able to metabolize foods. The yeasts in Kombucha are facultative anaerobs which will produce ethanol alcohol if there is no oxygen available. If there is oxygen available they will oxidize the available sugar into carbon dioxide and water. The acetic acid bacteria in Kombucha, are strict aerobes and require oxygen. They usually feed on the ethanol produced by the yeasts. However, they are also able to utilize other alcohols including glucose and may actually compete with the yeasts for the sugar. Since the zoogloea is floating on top of the K. tea, enough of the needed oxygen is provided to the acetic acid bacteria imbedded in its structure. The yeasts in the liquid down below are somewhat cut off from oxygen by the zoogloea and primarily use the anaerobic fermentative mode producing ethanol which in turn feeds the bacteria.
Black or green tea provides all the additional components and growth factors required by the Kombucha culture. It not only contains a number of important trace elements but also nitrogen compounds, carbohydrates, enzymes and vitamins. The stimulating components, caffeine and theophylline, belong to the purine groups which are required for building nucleic acids. Since these groups are used by the microorganisms, it could be assumed that the caffeine and theophylline in the tea are actually used up because they represent a source of nitrogen. What happens to the caffeine in Kombucha tea is a frequently asked question and this perhaps provides the likely answer. Total nitrogen in black tea represents 4.5% of the dry weight: 0.92% is found in soluble proteins, 2.51% is insoluble and 1.07% is contained in caffeine (for a tea containing 3.71% caffeine) and theophylline. According to one source (Abraham, 1995) green tea contains 5% caffeine and black tea only 2%. Green tea therefore provides more than twice the amount of nitrogen for the Kombucha culture. It is important to keep in mind that herbal teas do not contain these particular important nutrients and can for this and other reasons not be considered very suitable for making Kombucha.
Günther Frank (1994) already mentioned that Bing considers the purines - and caffeine belongs to this family - as providers of important nutrients for Kombucha. My assumption that the microorganisms in Kombucha do in fact break down caffeine to obtain critical nutrients is supported by an analysis performed by David Chappuis. He reported in a post to the Kombucha discussion group that he observed a reduction of caffeine by 25% during the first two weeks. (Feb. 28, 1998).
Here is the relevant part of a table he included:
|Analyte||0 Day||7 Day||14 Day||21 Day|
I would expect that theophylline, the other purine compound in black and green tea, gets similarly used up during the "fermentation" process.
For more information about yeast: What are Yeasts.
Abraham H. Wie entsteht die Haut auf dem Tee. PTA heute. 1995 (9): 908.
Brock T. Biology of Microorganisms. Englewood-Cliffs: Prentice-Hall. 1970. Campbell., N.A., Biology. 3rd edition. New York: Benjamin/Cummings Publishing Company.1993.
Chappuis, David. Yes, Caffeine Reduction During Brewing. Post to the Kombucha Internet Discussion Group, Februrary 28, 1998.
Frank, Günther. Kombucha, Healthy Beverage and natural remedy from the Far East. Steyr, 1994.
Gottschalk G. Bacterial metabolism. New York: Springer Verlag. 1979.Online Encyclopedia Britannica 1995.
Reiss J. Der Teepilz und seine Stoffwechselprodukte. Deutsche Lebensmittelrundschau 1987 (9): 286-290.
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Last updated 11/2/98