Alcoholic yeast in industrial alcohol production

General characteristics of yeast

Saccharomyces cerevisiae is a type of alcoholic yeast. Like all substances of this type, Saccharomyces cerevisiae are unicellular microorganisms of the class of ascomycetes or marsupial fungi. They are used to start the process of fermentation of sugar and its gradual transformation into alcohol. Saccharomyces cerevisiae reproduce by budding. If microorganisms live in an environment that is extremely depleted of nutrients, they can multiply by sporulation.

The microorganisms of Saccharomyces cerevisiae are mostly oval or elongated. Ovoid and ellipsoidal individuals can also be found. Their average size is 6-11 mm and depends on the type of yeast itself, as well as the conditions in which they live. The volume and length of the cell in yeast affect the rate of interaction of the microorganism with the nutrient medium. Therefore, the larger the volume and surface of the yeast cell, the faster and more intense their vital activity.

The yeast cell itself typically consists of a shell that accommodates other parts of the yeast body: the cytoplasm and the nucleus. The inner part of the yeast shell is represented in the form of protein substances, phospholipids and lipoids, when the outer part in its structure has polysaccharides and traces of chitin. The shell primarily regulates all other parts of the yeast body, and also allows the yeast to absorb certain substances.

Fig. Electronic micrography of a yeast cell: 1 — cell wall; 2 — cytoplasmic membrane of a yeast cell; 3 — cytoplasm; 4 — core; 5 — mitochondria; 6 — kidney

Yeast cytoplasm has a viscous structure. This feature is characteristic of yeast because of the protein substances in the base. In addition to proteins, the cytoplasm contains: ribosonucleoproteins, lipoids, carbohydrates. Also, there is a lot of water in the cytoplasm, which allows important enzymatic processes to take place. Young cells are distinguished by a homogeneous cytoplasm. With aging, uniform granularity appears in yeast cells, as well as vacuoles and fatty areas.

Chondriosomes or mitochondria in Saccharomyces cerevisiae are represented as granular formations or filaments. These parts of the cell are responsible for the accumulation of useful substances, which, after entering the cell, undergo special transient processes for further transformation. Mitochondria are also responsible for the activation of amino acids, which is only possible during the synthesis of proteins or other compounds.

Ribosomes of Saccharomyces cerevisiae are presented in the form of special inclusions of granular form. They consist of lipids, proteins and RNA. The latter are responsible for the synthesis of proteins and the activation of amino acids that come from the mitochondrial system.

The nucleus of a Saccharomyces cerevisiae cell is a body in the form of a ball or oval. It is surrounded on all sides in the cytoplasm, which does not dissolve it. The nucleus contains DNA and DKNP. Also, there is a large amount of RNA in the nucleus. DNA in yeast is responsible for the accumulation and transfer of information about the microorganism to inheritance.

Another mandatory part of Saccharomyces cerevisiae is vacuoles. Vacuoles are special clusters that form in plasma during aging of yeast cells. It is separated from the cytoplasm by a special shell - a vacuolar membrane, which consists of proteins and lipids. The shape of the vacuole is constantly changing and depends on the movement and concentration of the cytoplasm. Young yeast cells have vacuoles in the form of a certain number of small clusters. In older cells, vacuoles are represented as one large cluster. Vacuoles are responsible for the formation of compounds that undergo fermentation, and also form waste products. Young Saccharomyces cerevisiae cells have practically no fat accumulations. Some older cells have small inclusions of fatty elements. Old cells fat accumulates in large drops.

The reserve nutrient for Saccharomyces cerevisiae is glycogen. It is a substance from the group of polysaccharides structurally resembling amylopectin. It accumulates in media that are rich in sugar during the cultivation of alcoholic yeast. When sugar is in short supply, glycogen is quickly consumed. Mature cells have approximately 40% glycogen. Young individuals practically do not have this substance.

The appearance of yeast cells characterizes the general condition of the body. By staining, it is possible to determine the amount of glycogen, and as a consequence, the physiological state of yeast. In production, all stages of yeast cell life are used at once: young, mature, old and dead. Mature cells are the most effective in terms of fermenting energy.

For the production of alcohol, only those alcoholic yeasts that have sufficiently high fermentation properties are used. They must necessarily have an anaerobic type of respiration, ferment sugar quickly and fully, and also be sufficiently resistant to the products of their vital activity and the products of the vital activity of other microorganisms. It is important that the yeast can tolerate a large amount of salts and dry substances that may be present in the alcoholic wort.

Distilleries that specialize in the processing of molasses are common yeast race Ya. Races Yal and V. are used for bakeries . They do a good job with the fermentation of sucrose, glucose and fructose. Raffinose is fermented only by 30%. Therefore, the shortage of alcohol in such a situation is quite a large amount. Each percentage of raffinose during complete fermentation increases the alcohol yield by 1.46%.

The fermentation activity of yeast may be increased. This is possible due to the processes of mutagenesis or hybridization. To obtain yeast species with increased fermentation activity, the hybridization method is best suited. It is based on crossing two parent yeast species and breeding yeast races with pre-known, selected properties. Thus, a number of important, effective yeast hybrids have been obtained, which have advantages over the yeast races Ya and V. The hybrids received a special enzyme - a-galactosidase, which allows the complete fermentation of raffinose. Some yeast hybrids have received better baking properties, as well as increased generative function. Hybrid 112 showed better maltase activity, however, its alcohol accumulation is less by 1% when compared with yeast of race B. Hybrids 67 and 105 have the same alcohol yield as race B, but have a greater generative capacity. The G-67 race has increased resistance to a low pH environment. It produces more alcohol, while reducing the cost of sucrose on third-party products.

During the fermentation process of wort from raw materials that contain starch, yeast of race XII is used. They perfectly cope with the task of fermenting fructose, sucrose and maltose, but they do not ferment dextrins. Hydrolysis of dextrins is carried out during exposure to malt dextrinases. As a consequence, the entire fermentation rate of wort, which contains starch, depends on the rate of hydrolysis of dextrins.

Optimal habitat for alcoholic yeast.

Alcoholic yeast normally lives in a peculiar environment in which there is a certain temperature, pH level and chemical composition of the nutrient medium.

What should be the temperature, as well as the pH of the mash?

Alcoholic yeast can live normally at different temperatures. However, the range from 29 to 30 degrees Celsius is considered the most pleasant for them. Very high or low ambient temperature slows down or completely neutralizes the vital activity of yeast. The maximum permissible temperature of yeast is 38 degrees Celsius. The minimum temperature is 5 degrees. Other temperatures are not particularly pleasant for microorganisms, and at temperatures above 50 degrees, individuals die.

It should be borne in mind that the normal temperature for adequate and effective yeast development and the temperature at which the best fermentation activity manifests itself should not be the same. There are situations when yeast that has been grown at a temperature of 17-22 degrees can have a greater fermentation energy than other yeasts. If the composition is fermented at a temperature that exceeds 30 degrees, it may have a negative effect on the quality of the product. In order to preserve the enzymatic activity, lifting power and resistance of yeast, it is better to observe the temperature regime within 28 - 29 degrees. Liquid based on substances with starch is recommended to ferment in the limit of 28 - 32 degrees.

The rate of reproduction of wild yeasts and bacteria also depends on the increase in temperature, which can significantly exceed the rate of reproduction of saccharomycetes. For example, at a temperature of 32 degrees, the reproduction rate of wild yeast is 3 times higher and 8 times at a temperature of 38 degrees. Such rates of bacterial development also increase the level of acidity of the environment in which they live, which leads to a decrease in the level of alcohol yield. The level of acidity of the medium further affects the activity of the vital activity of alcoholic yeast. Hydrogen ions can affect the membrane of microorganisms. A certain concentration can either increase or decrease the ability of the shell to pass substances from the medium. Therefore, the level of acidity of the medium directly affects the rate at which yeast receives nutrients from the brew, which affects the activity of enzymes and the formation of vitamins by the bacterium. In addition, the pH level also affects the type of fermentation. Thus, if you shift the level of acidity towards alkalinity, the amount of glycerin in the medium will increase. The acidity level from 2 to 8 is considered optimal for the normal functioning of yeast. For growing yeast, the best option would be to keep the pH between 4.8 and 5. At pH levels lower, yeast can develop, albeit slowly. The development of lactic acid bacteria at levels below 4.8 stops completely. This feature of alcoholic yeast can be used to suppress some bacteria in the wort. The liquid is artificially acidified to an acceptable level, they wait for some time and return normal indicators.

Composition of the optimal medium for alcoholic yeast

The chemical composition affects how many nutrients are needed for the normal functioning of alcoholic yeast. It depends on the quality of the nutrient medium and the conditions in which yeast was developed and their physiological characteristics. If we analyze the chemical composition of a yeast cell, then it consists of 47% carbon, 6.5% hydrogen, 31% oxygen, 7.5% nitrogen and 1.5% phosphorus. Traces of other elements may occur slightly: calcium, potassium, magnesium, sodium, sulfur. Their number does not exceed 0.5% of the total mass. Also, some yeast may contain iron, copper or zinc residues.

Alcoholic yeast that succumbed to pressing contains almost 75% water and the rest of the dry matter. The total moisture content of the composition affects the ratio of the amount of intracellular and intercellular moisture. That is, the removal of water from the composition of alcoholic yeast as a whole does not affect their viability at temperatures within 50 degrees.

The dry parts of yeast consist of 25% organic parts: 13% protein, 6% glycogen, 2% fat, 2% cellulose. Yeast also has up to 5% ash.

Learn more about the composition of the yeast medium:

• Squirrels

Raw protein in yeast is about 50%, true in the region of 45% of the total amount of proteins. Thus, in the composition of raw protein, all compounds of nitrogen and nucleic acids can be found in the form of purine and pyrimidine amino acids.

• Glycogen

In cases where there are no substances necessary for yeast in the nutrient medium, glycogen is converted into alcohol or carbon dioxide.

• Trehalose

Trehalose is in the cell together with glycogen, because it is a fairly mobile carbon, which is considered a reserve and is an element to ensure the stability of yeast that is used for bakeries. The amount of such carbon in the yeast cell increases depending on the reduction of nitrogen in the medium or changes in the acid level of the medium to below 4.5.

• Fats

Oleic, linolinic and palmitic acid act as fats in alcoholic yeast.

• Ash

It is presented in the form of basic oxides.

• Phosphorus

The element is contained in the form of organic or inorganic phosphates. These parts are part of the molecules of nucleic acids, coenzymes and thiamine, namely, traces of phosphorus can be found in the nuclear substances of cells. The element is important during the passage of various energy processes in yeast cells.

• Sulfur.

Sulfur in alcoholic yeast is represented in the composition of amino acids and vitamins. It can also be found in the composition of enzymes as sulfide and thiol groups.

• Iron

Iron takes part in the work of important enzymes, such as zymogenase and pyrophosphatase, and is also found in enzymes that are responsible for cell respiration.

• Magnesium

Magnesium is responsible for the activation of phosphatase and enolase in alcoholic yeast. The ions of the chemical element effectively cope with maintaining the activity of some enzymes during temperature rise. In addition, magnesium helps yeast process glucose faster: the higher the glucose in the yeast habitat, the more effectively magnesium copes with this task. The optimal nutrient medium should have around 0.05% magnesium. In a way, with the help of magnesium, the fermentation process can be regulated by adjusting the amount of ions in the medium.

• Potassium.

The element is necessary for two functions: nutritional and for the reproduction of alcoholic yeast. Potassium takes part in the oxidative process and the process of glycolysis. Therefore, in fact, potassium helps regulate and stimulate the movement of phosphorus inside the yeast cell.

• Calcium

Calcium is used by yeast to activate processes in the microorganism. Calcium ions bind to ATP and inhibit some yeast enzymes. Increasing the amount of calcium ions inhibits yeast reproduction, reduces the ability of yeast to accumulate glycogen and increases the % amount of sterols. In numbers, calcium up to 40 mg per 1 liter of yeast liquid increases the ability of yeast to multiply. More inhibits reproduction.

• Trace elements.

Trace elements also take an active part in the process of yeast reproduction, as well as support from normal life. In fact, trace elements are included in all the compositions of enzymes, vitamins or other compounds that take part in synthesis. In addition, trace elements can regulate the speed, as well as the peculiarities of the course of certain chemical processes in the environment. Cobalt helps yeast to multiply, increases the amount of nitrogen and nitrogen substances in yeast cells. It increases the synthesis of vitamin substances, riboflavin, ascorbic acids, etc.. Trace elements enter into compounds with other enzymes and elements, which causes their stimulating effect. The effect of stimulation directly depends on the quality and strength of the connection that has arisen.

• Vitamins and other particles

An equally important factor for the optimal development of alcoholic yeast, as well as effective fermentation, are vitamins, which are used as cofactors in enzymes. By themselves, yeast can synthesize almost all vitamins. The exception is biotin. It must be in a nutrient medium.

Among other particles, fatty acids can be distinguished, which affect the growth of yeast. The most stimulating is oleic acid with 18 carbon atoms. However, the concentration of acid in the nutrient medium should not be large, in the range up to 0.5 mg / ml. an increased concentration of oleic acid, on the contrary, slows down the growth of microorganisms.

Nutrition and its sources for alcoholic yeast

Alcoholic yeast feeds exogenously and endogenously. During exogenous feeding, the microorganism receives nutrients from the external environment. Endogenous nutrition implies the use of reserve substances that were accumulated earlier. This method is "triggered" when the cell is starving. She begins to consume glycogen, trehalose lipids, etc..

Carbon nutrition of alcoholic yeast.

Carbon is quite an important element for alcoholic yeast. They use it for various organic compounds. For example, for glucose, mannose, fructose or galactose. It is also important to take into account the sequence with which the yeast cell consumes carbon sources. First of all, yeast consumes glucose and fructose. Yeast race affects the sequence of fatty acid intake by yeast. This sequence is also affected by the composition of fatty acids. Acetic acid is absorbed by cells along with glucose. The tendency of carbon uptake corresponds to which of its sources most affects the rate of cell growth.

During continuous cultivation of alcoholic yeast cells, more carbon remains in the yeast habitat. In this case, it will be absorbed by the cells last.

The absorption of substances also depends on the type of yeast. Wild yeast is good at assimilating galactose, and yeast of the Cand type. Clausseni absolutely do not absorb it.

In order for yeast to absorb maltose and sucrose normally, the enzymes start the hydrolysis process to neutralize disaccharides into monosaccharides. During the transition of yeast from an anaerobic state to an aerobic one, they stop fermenting maltose and glucose, but their sucrose activity increases by 3 times. Maltose alcoholic yeast begins to consume only after the medium runs out of fructose or glucose, but full fermentation of maltose still takes place during the stationary phase of growth of alcoholic yeast.

No less important during dissimilation and synthetic processes is organic acid. Yeast, depending on the species or race, can use fatty acids as a carbon source. For example, yeast can consume acetic, pyruvic, lactic, butyric and other acids if their concentration is normal. Potassium salts and acids with carbon atoms in the molecules also stimulate the growth of alcoholic yeast. They are able to accelerate the growth process up to 3 times when compared with other acid molecules.

Fatty acids, which have an average carbon chain length, are practically not consumed by alcoholic yeast. Low concentrations of such acids are acceptable for the nutrient medium, but high concentrations can inhibit the growth of microorganisms. Acids with long carbon chains of 12 to 17 atoms in molecules are consumed depending on what type, genus and race of yeast.

In addition, alcoholic yeast can use products from the Krebs cycle as carbon sources. Namely: fumaric, malic, citric, succinic, and pyruvic acid can act as elements for carbon nutrition.

Nitrogen nutrition of alcoholic yeast.

Alcoholic yeast can consume all the amino acids that are in the yeast proteins due to inorganic nitrogenous compounds. A type of Sacch yeast. Cereviesiae is capable of assimilating only two forms of nitrogenous compounds, namely ammonia compounds and organic compounds. Yeast is able to absorb nitrogen sulfate, urea, ammonium phosphate and ammonia salts of fatty acids. If there is a sufficient amount of sugars in the medium, ammonia salts are used only to provide the cell with a sufficient amount of nitrogen. In the process of nitrogen consumption by the yeast cell, the acidity of the medium changes due to the release of acids into the medium. Ammonia nitrogen is best absorbed by alcoholic yeast.

It should be borne in mind that amino acids in the medium are both sources of carbon and nitrogen at the same time. Nitrogen is formed due to the cleavage of amino groups from ketoacids and is absorbed by yeast cells. Amino acids can also be absorbed from the nutrient medium if there is a sufficient amount of sugar in it, as well as a complete set of these acids. This nuance allows you to reduce the consumption of sugar to feed alcoholic yeast and significantly increase the yield of alcohol during the fermentation process. The same process guarantees the synthesis of proteins, as well as enzymes, including those that are already present in the cell.

Organic nitrogen can be consumed by yeast only if there is a sufficient amount of vitamins, namely biotype, thiamine and pyridoxine. Choline, purine, betaine, as well as other nitrogenous compounds of a similar type, yeast is not able to digest. Peptides are partially absorbed. Their consumption depends on the complexity of the element: with increasing complexity, assimilation decreases significantly. The permissible amount of peptides ensures the absorption of amino acids.

The amount of nitrogen in yeast can tell you under what conditions the cells were cultured and what their physiological state is at the moment. The nitrogen content in the cells also depends on the amount of nutrients that are additionally introduced and on the type \ race of yeast. In general, the amount of nitrogen in yeast ranges from 7 to 10% per unit of dry matter.

Phosphoric nutrition of alcoholic yeast.

The anaerobic environment ensures the absorption of phosphorus by yeast during the initial fermentation period. Its consumption during this period is from 80 to 90% of the total content in yeast. Young cells that actively reproduce have more phosphorus in their composition compared to older cells. The trend is clearly seen in the dry matter of mixtures: in the first 6 hours of fermentation of alcoholic yeast, 2% phosphorus is observed, when by the end of fermentation in the region of 1%.

In the medium with starch raw materials, there are phosphorus-containing compounds necessary for alcoholic yeast. In other food media, it is necessary to add orthophosphoric acid for the normal course of fermentation.

Other factors that affect the reproduction of alcoholic yeast

In addition to the parameters described above, the rate of yeast reproduction is affected by osmotic pressure in the cell of the microorganism, as well as its habitat. With increasing pressure, the rate of reproduction also increases.

It is possible to stimulate additional growth of alcoholic yeast by exposing them to ultrasound. After such treatment, invertase activity increases several times in yeast. Ultrasound also affects baking yeast quite effectively. In an hour of such exposure, it is possible to increase the lifting force of yeast by 15-18% and increase their amount of ergosterol by 45-60%. The effectiveness of exposure depends on the frequency of ultrasound.

Wine yeast shows the best fermentation results under the influence of Y-rays. Also, under such treatment, baking yeast increases maltase activity. However, if yeast is irradiated with ultraviolet rays for a long time, then they lose their abilities, namely, they stop synthesizing leucine or isoleucine. Because of such experiments, it is possible to obtain mutated cells that cannot secrete isobutyl and isoamyl alcohol. Baking yeast is affected by ultraviolet rays in a different way: they increase their maltase activity several times.

Weak alkaline solutions, as well as alcohols or esters, negatively affect yeast cells by dissolving their lipoid substances. Thus, alcohol with a relatively small volume in the nutrient medium can significantly slow down the reproduction of yeast. But, if a sufficient amount of nutrient medium is supplied, yeast can multiply with a high concentration of alcohol. Even with a proportion of 10% alcohol, yeast continues to ferment sugar, since the reproduction and development of cells depends on the amount of nutrients in the brew, and not on the amount of alcohol in it. In order to neutralize the effect of alcohol in the composition on yeast, there is a developed scheme that ferments the composition under vacuum.

Formalin and heavy metal salts negatively affect the vital activity of yeast. Even the smallest part of these substances in the composition reduces the rate of development and reproduction of alcoholic yeast. Also, sulfurous, nitrogenous and hydrofluoric acid spoil the habitat for yeast. Small concentrations of substances reduce cell growth, as well as significantly impair their quality and lifting power.

Sulfuric acid in volumes from 0.35 to 0.6% does not affect the viability of yeast cells at the initial stages. After a day of yeast in this composition, about 2% of individuals die. Milk bacteria in a composition with such a consistency die after 2 hours, and if you increase the composition of the solution to 0.5%, all bacteria die in 2 hours. Wild yeast is more stable and can withstand a solution with a proportion of 1.3% sulfuric acid for more than two hours.

Organic acids of the free type inhibit yeast more effectively than salts. Even small concentrations of acids can suppress the normal life of yeast, as well as accelerate their death. Butyric and caproic acid are the most affected. An increase in the suppression effect from acids is observed from a decrease in the acidity of the medium to 4 points. After a day of this effect, many plasmolized yeast cells can be observed.

It is possible to reduce the ability of yeast reproduction without increasing the number of dead cells due to formic acid. Also, you can use acetic acid, which has a weaker effect.

Butyric acid (0.045%), caproic acid (0.055%) formic acid (0.09%) propionic acid (0.12%) and acetic acid (0.45%) can reduce alcohol yield if a synthetic medium with 13% sucrose composition is fermented. The decrease is observed only if Race V or Ya yeast is used, race G - 176 and G - 202 work normally. Such concentrations of acids can be found in molasses, but there are fewer organic acids in this solution, and formic and propionic acid sometimes does not reach the desired indicators.

Butyric and capronic acid blocks fermentation and inhibits the release of alcohols in yeast of all races.

Silver or copper in certain amounts can kill yeast. In extremely small amounts, heavy metals inhibit cell development. The effect of metals on yeast depends primarily on the composition of the entire medium, its acidity level, temperature or the number of cells per gram of mash. For example, copper can be more aggressive for yeast in acidic environments, and silver manifests itself in ammonia solutions.

Furfural in the yeast habitat slows down cell reproduction by reducing the number of yeast buds, as well as their size. Small consistencies of this element in habitats reduce the maltase and zimase activity of microbial cells.

Sulfanol as an element suppresses yeast, but negatively affects lactic acid bacteria. Chlorine, in turn, destroys organic substances by oxidizing them.

Ca, Mg, Fe ions in an increased amount destroy the aqueous envelope of yeast. Thus, there is a possibility of yeast agglutination, which also creates an electric charge on the surfaces of yeast cells.

Yeast itself has a negative electrokinetic potential. Therefore, they adsorb elements on the surface - melanoidins, which already have a positive potential value. If you lower the acidity of the yeast habitat, the potential of the elements increases, which also increases the adsorption processes of yeast cells. A large number of melanoidins negatively affect cells, stain them dark and inhibit vital activity until the death of the cell. The enzymatic activity and the activity of invertase and catalase are also reduced. The presence of an element in the medium within the limits above the norm reduces the yeast population by half in less than a day. Do not forget that these elements may appear in the medium after the starch-containing raw materials are boiled.

If the acidity of the washing water is normal, then the coloring substances of the yeast cell are not amenable to desorption. Indicator 3 is considered normal. Desorption starts from pH at level 9.

Cysteine, glutathione, and other sulfhydryl compounds can activate some yeast cell enzymes. They promote the start of fermentation, as well as activate and regulate the work of enzymes. This is important for normal functioning and metabolism in yeast cells.

Sulfhydryl compounds are extremely important participants in electron transfer through cytochrome. Glutathione and cysteine promote faster alcoholic fermentation due to thiol enzymes, which are observed during the oxidation of sugar. But, this method is not effective in terms of price, the elements are quite expensive. In practice, yeast autopolysate is used.

The process of fermentation and respiration of yeast cells.

Anaerobic breakdown of carbohydrates.

Under anaerobic conditions, enzymatic carbon dissimilation occurs with significant energy release. In addition, it leads to the release of incomplete oxidation products, which is called fermentation.

During the fermentation process, organic compounds act as carbon acceptors. Oxygen does not take part in these processes, and compounds appear as a result of oxidation.

The figure shows a detailed diagram of all the chemical processes that are observed during glucose fermentation.

1) First, the formation of phosphoric esters of Sugars occurs. The enzyme hexokinase and adenylic acid, which are considered phosphoric acid donors, convert glucose into glucopyranose-6-phosphate. The phosphoric group from ATP to glucose is transferred due to the process of catalysis by hexokinase. The remainder of phosphoric acid is then attached in place of the 6 carbon atom. Magnesium activates the action of the enzyme. According to the same principle, the conversion of fructose and mannose is carried out, and the glucose reaction is responsible for the speed of the entire fermentation.

2) Then the resulting phosphate undergoes isomerization processes due to the enzyme glucose phosphate isomerase. The reaction is reversible, resulting in fructose - 6 - phosphate.

3) The resulting element is susceptible to the action of the enzyme phosphofructoknase. Thus, the phosphoric acid residue is attached to the place of the first carbon atom and due to ATP we get a new element - fructose - 1.6 - diphosphate. The transformation reaction is not reversible, and the sugar molecule passes into the labile state of the oxoform and becomes ready for further action and transformation by reducing the bond strength between 3 and 4 carbon atoms.

4) the enzyme aldolase triggers the decomposition of fructose 1.6 diphosphate into two parts of phosphotriose - -­phosphoglycerine aldehyde and phosphodioxyacetone. This reaction is reversible.

5) The isomerization process begins between the obtained phosphotrioses due to the catalysis of the enzyme triose phosphatisomerase.

6) During the induction period until the formation of acetic aldehyde, the dismutation reaction between the aldehyde molecules begins. It is started by the enzyme aldehydmutase paired with a water molecule. One molecule of phosphoglycerin aldehyde is reduced as a result and receives phosphoglycerin. The second molecule is oxidized and forms 3 phosphoglyceric acid. Phosphoglycerin does not take part in further reactions and is a by-product of fermentation with the release of alcohol.

Further oxidation of 3 phosphoglyceric acid is carried out in a complex way. First of all, it is converted into 1,3-diphosphoglycerin aldehyde, which attaches to itself the remains of inorganic phosphoric acids. Then, the enzyme triosophosphate dehydrogenase acts on the resulting aldehyde and oxidizes it into 1,3-diphospho-glycyrinic acid.

7) phosphotransferase takes part in the reaction of the phosphoric acid residue, in which a macroergic bond remains and is transmitted with 1,3-diphosphoglycerol acid. The energy that is released during the oxidation of the aldehyde is accumulated in ATP.

8) The enzyme phosphoglyceromutase affects the result, and the acid is amenable to isomerization into 2-phosphoglyceric acid.

9) As a result, after the distribution of energy within the molecules, 2-phosphoglyceric acid is converted into phosphoenolpyruvic acid. The catalyst of the reaction is enolase, which is activated by magnesium ions. In order to maximize the effect of enolase, it is necessary to reach the acidity of the medium from 5.2 to 5.5 points. Other parameters cause aggregation of enolase molecules.

10) phosphotransferase and potassium contribute to the transfer of phosphoric acid residue to ADP, and the energy from the reaction is accumulated in ATP.

11) The result in the form of acid passes into a stable ketoform.

12) Carboxylase acts on pyruvic acid and cleaves off carbon dioxide, which allows acetic aldehyde to be transformed.

13) Alcohol dehydrogenase begins the transfer of hydrogen to acetic aldehyde, which promotes the formation of the desired ethyl alcohol, and also regenerates NAD.

Aerobic breakdown of carbohydrates

The breakdown of carbohydrates in aerobic conditions is almost the same as in anaerobic conditions. The difference is that the formation of pyruvic acid is carried out by its complete oxidation to carbon dioxide and water in the tricarboxylic acid cycle. This cycle implies the sequential course of oxidative and reducing processes that transfer hydrogen to molecular oxygen, which is considered the last acceptor. The transfer is possible thanks to carrier molecules, which also form a chain of respiration of cells. The scheme of reactions of chemical elements during the aerobic breakdown of glucose is shown below.

Glucose catabolism forms two molecules of the pyruvic acid we need. At the beginning of all processes, the first molecule undergoes decarboxylation. As a result of this process, we obtain activated acetic acid.

SN3 · CO · COON + CoASN + NAD — SN3-CO ~ CoASN + NAD · H2 + CO2

The second acid molecule lends itself to the enzyme pyruvate carboxylase. As a result, it condenses with carbon dioxide molecules. As a result of the reaction, oxaleacetic acid is obtained.

SN3 · CO · COOH + CO2 + ATP ↔ HOOC · CH2 · CO · COOH + ADP + F

Oxaleacetic acid can be obtained from malic acid.

The whole cycle of tricarboxylic acids implies the beginning with the condensation reaction of acetyl - CoA together with a molecule of oxaloacetic acid or oxaloacetate. The enzyme catalyst in this reaction is citrate synthase. As a result of the reaction, we obtain citric acid, as well as coenzyme A of the free type.

The subsequent reactions are shown in the diagram. One such revolution of a pyruvic acid molecule implies the addition of three water molecules to it and the release of H2 with CO _{2 molecules.} The equation looks like this:

SN3 · CO · SOON + 3N2O — > 3S0 ₂ + 10 N.

In the cycle of tricarboxylic acids, not only carbohydrates break down. CTC also promotes the breakdown of fatty acids and amino acids.

Decays in an anaerobic and aerobic way deliver the necessary amount of energy to yeast, and also ensures the normal synthesis of bioelements. For example, oxaloacetic and a-ketoglutaric acid are amenable to the reduction process by amination and transamination, which makes it possible to obtain aspartic and glutamic acid as a result. In general, the production of aspartic acid is possible from fumaric acid. The production of these acids occupies an important place during the synthesis of proteins from carbohydrates. To obtain the desired biomass, the cells of alcoholic yeast interact with other elements. For example, cells may choose the anaplerotic pathway, in particular the pentose phosphate pathway. These elements are considered ancestral elements of nucleotides and corresponding acids.

The oxidation of sugar has a much larger amount of energy that is released. Thus, as a result of the reaction, it is likely to obtain a larger number of metabolites that are ready for further reactions and synthetic processes. Because of this, the rate of growth and reproduction of yeast cells increases markedly, as does their biomass.

The amount of sugar consumed during biosynthetic fermentation processes.

Yeast generation involves a complex process that is based on a certain number of complex closely related chemical reactions. It is impossible to unambiguously calculate how many nutrients will be needed to generate yeast. Therefore, theoretically approximate practices are used, which allow us to calculate the total amount of biosynthesis and fermentation.

Based on research, it has been proven that sugar is used most of all to produce yeast from molasses. To obtain finished marketable products, approximately 64.6% of sugar is lost, taking into account all losses during fermentation. In more modern factories that specialize in certain methods, this indicator is slightly lower.

During yeast production, sugar is consumed in order to obtain three products, namely the yeast itself, alcohol and carbon dioxide. In order for sugar to be used as efficiently as possible, all these products must be disposed of. During alcoholic fermentation, sugar from molasses is consumed almost without loss for the formation of the necessary products. Unfrozen sugar remains in the molasses in the region of 2-3%. Sugar losses in such a process amount to approximately 7 to 12% of the sugar that was introduced into the process. Therefore, the net alcohol yield ranges from 88 - 93% of that which was calculated theoretically. The amount of glycerin that is formed from fermentation affects the composition of the nutrient medium, as well as its physical and chemical parameters.

The amount of obtained biomass of yeast cells, as well as the stage of their active life depends on the direction of the fermentation process. The consumption of sugar for the formation of biomass also depends on this. In the process of working with mature mash to obtain baking yeast, they try to get as much yeast biomass as possible. By themselves, yeast can be re-directed to fermentation, which increases the amount of biomass without compromising sugar consumption. When using yeast several times, their energy does not decrease, but on the contrary increases. The intensity of fermentation from this also increases, due to a larger amount of alcoholic yeast.

A lot of sugar is used for the normal respiration of yeast cells during yeast production. In numbers, this is about 6 - 15% of the amount that is used in general. This expense is not stable. It may depend on the concentration of sugar in the nutrient medium, as well as the rate of oxygen saturation of the composition, temperature or other indicators. Based on this, there are ways to increase the amount of alcohol produced during the processing of the composition.

Theoretically, based on the equations of yeast operation, 66.7% of carbon from sugar is converted into alcohol, and the remaining part is converted into CO2. Therefore, the amount of carbon that goes into building biomass and respiration depends on the amount of explicit sugar in the habitat.

An increase in the concentration of sugar in the yeast nutrient medium affects the amount of biomass produced and reduces the CO2 output during yeast respiration. That is, fermentation with this approach is more economical.

Lowering the temperature of the brew reduces the sugar consumption for yeast respiration, and an increase in the intensity of oxidative reactions affects a lower yeast yield.

Microorganisms living with yeast

During the fermentation process, it is extremely important to protect the yeast from unwanted other microorganisms that may interfere with the normal operation of the yeast. These may be extraneous bacteria or wild yeast races that enter the nutrient medium accidentally with water, air or other types of raw materials. After getting into the devices in which fermentation takes place, extraneous microorganisms can accumulate and eventually displace the desired yeast culture. In addition, foreign bacteria consume part of the sugar from the mash, which generally reduces the amount of final alcohol. Also, they can synthesize extraneous organic acids, enzymes and other products that lead to the fermentation of the medium, as well as a decrease in the properties of yeast. As a result, the amount of starch and unfrozen sugar in the mash increases.

Details about extraneous microorganisms

Lactic acid bacteria

In total, there are several types of lactic acid bacteria, namely cylindrical, rod-shaped, spherical, spherical, gram-positive, immobile and non-spore-forming. Lactic acid bacteria of the heterofermentative type, like lactic acid, realize volatile acids, alcohol and hydrogen.

Lactic acid bacteria grow best at a temperature of 20-30 degrees. Thermophilic species of lactic acid bacteria grow best at temperatures 20 degrees higher. At the same time, like other microorganisms, lactic acid bacteria die at temperatures from 70 to 75 degrees.

Most often you can find such groups of bacteria: Lacto. bacillius plantarum, Lact. breve, Lact. fermentii, Leuconostoc mesenterioides, leuc. agglutinans. Bacteria with the specific name Leuconostoc mesenterioides are framed in a mucous capsule that allows them to withstand high temperatures and exposure to acids. In a liquid medium, they die at a temperature of 112 degrees in 20 minutes. They can live in a solution of sulfuric acid for an hour. Leuc. Agglutinans can stick to yeast and also glue their cells together.

Acetic bacteria

Acetic bacteria are represented as gram-negative, rod-shaped or undisputed individuals that are exclusively aerobic cells that live in a yeast-like environment. Acetic bacteria can act as an oxidizer on alcohol and acetic acid may result. Similarly, propionic acid is obtained from propyl alcohol, butyl alcohol is obtained from butyl alcohol. Some types of bacteria can also affect glucose by producing gluconic acid or xylose by producing xylonic acid. However, ordinary ethyl alcohol is considered the main means of vital activity of such bacteria. The most common types are: Acetobacter aceti, Acet. Pasteurianium, Acet. oxydans. These are rod-shaped individuals up to 3 microns. Sometimes, they are connected in chains. They live in an environment from 20 to 35 degrees. The first type of bacteria can withstand an alcohol concentration of up to 11%. Yeast slows down its growth and development if the number of such bacteria, as well as their waste products, becomes a lot.

Butyric acid bacteria.

Butyric acid bacteria are represented in the form of large and mobile rods up to 10 microns long. They are spore-forming and exceptionally anaerobic. The spores of such bacteria are presented in the form of cylinders or ellipses. In addition to butyric acid, when oxidized, they can produce acetic, lactic or capronic acid, but in smaller quantities. In addition, the production of ethyl or butyl alcohol is possible. Such fermentation spreads well in pumping stations, pipes or similar hidden places. The temperature for normal life is from 30 to 40 degrees. The acidity of the medium is up to 4.9 points. In other environments, butyric acid bacteria do not develop.

It is not acceptable to observe butyric acid bacteria during the production of alcohol, since the acid they produce suppresses the normal operation of yeast.

Putrefactive bacteria

Putrefactive bacteria are the types of bacteria that are responsible for the breakdown of protein substances. They can live in both aerobic and anaerobic conditions. Under aerobic conditions, they are able to completely mineralize protein to carbon dioxide. In anaerobic environments, toxic substances accumulate in the environment, as well as other organic compounds. Bacteria move well, are resistant to high temperatures, and also form spores. Normal temperature ranges from 36 to 50 degrees Celsius. Anaerobes include E. coli and Proteus vulgaris. To aerobic Clostr. Nutrificum and Clostr. sporogenes.

Putrefactive bacteria have a particularly negative effect on the yeast of baking races. They significantly shorten their shelf life. Some putrefactive bacteria can form nitrites, which noticeably slow down the reproduction of yeast.

Wild yeast

Yeast that is considered dangerous for the production of alcohol. They consume many times more than ordinary yeast sugar, while releasing little alcohol. Cultured yeast does not take root well with wild cells. Many types of wild yeast convert sugar into org. Acids, as well as engaged in the oxidation of alcohol.

Microflora of water and air.

The water that is used to prepare the habitat should not contain more than 100 bacteria per milliliter. Large alcohol plants use water from reservoirs with microorganisms of the following types: Esch. coli, Esch. freundi (Bact.citrovorus), Klebsiella aerogenes, Acrobacter cloacae, Bac. Subtilis, Bac. Mesentericus, Pseudomonas nonliguefaciens.

However, in one milliliter of such water there may be a lot of acidic bacteria. Therefore, it is pre-chlorinated in order to stabilize the number of microorganisms. Sodium hypochlorite, lime chloride or calcium hypochlorite are used in this case. Up to 40 mg of active chlorine is needed for one liter of such water. After disinfection, water can be used for technological purposes. Sometimes you can use dichlorantin. This drug is non-toxic and contains almost 70% of active chlorine. It is easily soluble in alcohol, as well as chlorinated carbons, while poorly soluble in water. If the active chlorine in the water remains at a level of up to 20 mg / l, spore-forming bacteria do not die. Thus, even more alcohol is obtained as a result due to improved alcoholic fermentation.

The air is also amenable to purification, since a huge number of microorganisms enter the composition with it, which negatively affect the production of alcohol and the properties of baking yeast. Workshops with feed yeast in factories are also cleaned. Bacteria of the following types live in the air: Bac. Mesentericus, bac. mycoides, Bac. megatherium, Bac. subtilis, bacteria of the genus Pseudomonas, sarcins (Sarcina lutea), spores of mold fungi of the genus Pennicilium and Aspergillus, yeast-like fungi of the genus Candida. Sometimes lactic acid bacteria are found.

Purification occurs due to the air being drawn in by blowers from places that are furthest from the ground (sometimes even above the roof of the plant). After that, oil filters are installed on them, which carry out primary cleaning. Wet-air pumps require the installation of filters on the suction ducts. Turbo blowers require the installation of filters on the discharge lines.

"Laik" filters are often used. Hydrophobic fabric acts as a filter material. Air with such a filter can be cleaned for 3 months without the need for fabric replacement. The purity of the air is maintained in the range of 97-99%. There are filters that use glass wool as a filter material.

Naturally Pure yeast culture.

Naturally pure culture is yeast that can be grown under optimal conditions, under which foreign microorganisms are moderately fed with inhibition of development.

The growth temperature of the added microorganisms and yeast is almost the same. It also runs off with the temperature of normal alcoholic fermentation, and therefore the medium is regulated by sulfuric or lactic acid by changing the pH of the medium. Of course, the pH is not so pleasant for the active reproduction of yeast, but this approach allows you to obtain a microbiologically pure culture.