Struktol antifoam agents for fermentative processes
General
The generation of foam during fermentation processes is caused by the existence of foam-active substances in the fermentation broth, escaping gas/air and turbulences within the fermenter. In most cases the substrates used are high in carbohydrates, which are partly converted into sugar substrates by enzymes. Sugars, starches and proteins act as the foam promoting substances themselves and they may be assisted by other substances or ingredients that partly consist of trace elements for the microorganisms. Furthermore, amino acids and proteins, which are generated by the microorganisms during the fermentation, can cause considerable foam activity.
Anaerobic/aerobic fermentation processes
The nature of the released gases depends on the fermentation method. Basically we have to distinguish between anaerobic and aerobic fermentation processes. The production of alcohol is a typical example of anaerobic fermentation. During this process substrates containing different sugars and starches are transformed by using yeast into alcohol and carbon dioxide. Depending on the substrates used more or less foam is formed by the escaping carbon dioxide. However, aerobic fermentation processes are much more important for the use of antifoam agents. In this case we have to distinguish between processes for the propagation of microorganisms (as for example the production of baker's yeast) and the production of different "biotechnology products" (as for example antibiotics and enzymes) by using special microbes. During aerobic processes air is blown into the fermentation vessel in order to supply the microorganisms with oxygen. The excess air is released and generates foam. Usually aerobic processes are considerably more foam intensive, because the quantity of air released is significantly higher than the quantity of carbon dioxide released during anaerobic processes.
Dosage of antifoam products
Without the use of antifoam agents fermentation vessels would overflow, which would lead to considerable losses of product as well as to soiling of the plant and other disadvantages. In most cases the antifoam is added into the upper area of the fermentation vessel. The addition is controlled by a foam probe. Schill+Seilacher "Struktol" GmbH developed a dosage system of this type, used succesfully in a large number of plants for several years. The dosing procedure depends on the fermentation progress. Usually the required quantity of antifoam is automatically and continuosly added to the system during the whole fermentation process and the dosage can be adjusted as required. Other foam controlling procedures in fermentation processes are, to fill fermentation vessel with substrates and the antifoam agents in order to prevent frothover during fermentation start.
Antifoam selection
The most important criteria to choose the best antifoam are effectiveness and not having any negative influence on the fermentation process concerning final product quality and yield. This results in an optimum yield and improved quality of the final products.
Product purification
After the fermentation process is completed, the final products have to be separated from the fermentation broth. The procedures for this isolation can be completely different and depend on whether the final products are either liquid or solid. Schill+Seilacher "Struktol" GmbH has developed a special product range for the fermentation industry. An accurate antifoam selection provides best fermentation results.
ALCOHOL PRODUCTION
A typical example of anaerobic fermentation is the production of alcohol. Here, several sugar-and starch-containing substrates are converted into alcohol and carbon dioxide using yeast. Caused by the escaping carbon dioxide more or less foam is formed depending on the substrates used.
AMINO ACIDS
Aerobic fermentations are an important application field for the use of antifoam agents. They can be distinguished in processes for growth of microorganisms (e.g. baker's yeast production), and the production of various "bio"products (such as antibiotics, enzymes, amino acids and citric acid) by using particular types of bacteria. In aerobic processes, the oxygen supply to the microorganisms is carried out by air blown into the fermenter. The air in excess is released and forms foam. Aerobic processes are usually very foam-intensive, since the amount of escaping air is much larger compared to the amount of carbon dioxide in anaerobic processes.
ANTIBIOTICS
Aerobic fermentations are an important application field for the use of antifoam agents. They can be distinguished in processes for growth of microorganisms (e.g. baker's yeast production), and the production of various "bio"products (such as antibiotics, enzymes, amino acids and citric acid) by using particular types of bacteria. In aerobic processes, the oxygen supply to the microorganisms is carried out by air blown into the fermenter. The air in excess is released and forms foam. Aerobic processes are usually very foam-intensive, since the amount of escaping air is much larger compared to the amount of carbon dioxide in anaerobic processes.
BIOETHANOL
The generation of foam during the production of bioethanol is caused by the presence of foam active substances in the substrates (sugar-, starch based) e.g. proteins and by-products.
Struktol antifoams are effective during the preparation of the substrate, during the fermentation and the distillation process. It is possible to add the antifoam already during the preparation of the mash. Most recommended is the dosage from the top of the fermenter directly onto the fermentation broth or into the circulation pipe, by using an automatic dosage system with foam probes. Further addition is generally not necessary, because Struktol antifoams are carried through the whole process incl. DDGS. In some rare cases a dosage into the distillation and DDGS processing could be necessary.
The dosage rate of antifoam depends on several parameters. Most influencing is the type of process: continuous production requires more antifoam than batch process. But also other process parameters, such as the filling height of the fermenter, substrate in use, etc. have huge influences.
The most effective antifoam product, necessary dosage quantities and best possible addition points depend on a.m. factory conditions and must be found out for each individual factory by carrying out work trials.
BIOGAS
Biogas is produced during the anaerobic digestion of organic material. Substrates are specifically grown energy plants like maize, previously unused parts of plants, liquid manure, wastewater sludge and other bio-waste. The organic material is biodegraded by microorganisms into biogas, which is a mixture of mainly methane and carbon dioxide. In many cases the organic material also contains foam active substances like proteins. During digestion disturbing foam might occur if the process in not correctly driven and foam active substances are present: inside the digester, during the isolation of the biogas from the digestion substrate, during the digestate evaporation etc.
The selected Struktol antifoaming agents are well balanced between destruction of already built foam, prevention of foam and degassing of high viscous digester content.
A good distribution of the antifoam in the digester is important. The best addition point would be into the substrate just before it is pumped into the digester. For the digestate evaporation the best addition point would be after the decanter and after the adjustment of the pH-value.
Addition rates depend on the amount of foam activity and must be found out by pretests.
CITRIC ACID
Aerobic fermentations are an important application field for the use of antifoam agents. They can be distinguished in processes for growth of microorganisms (e.g. baker's yeast production), and the production of various "bio"products (such as antibiotics, enzymes, amino acids and citric acid) by using particular types of bacteria. In aerobic processes, the oxygen supply to the microorganisms is carried out by air blown into the fermenter. The air in excess is released and forms foam. Aerobic processes are usually very foam-intensive, since the amount of escaping air is much larger compared to the amount of carbon dioxide in anaerobic processes.
ENZYMES
Aerobic fermentations are an important application field for the use of antifoam agents. They can be distinguished in processes for growth of microorganisms (e.g. baker's yeast production), and the production of various "bio"products (such as antibiotics, enzymes, amino acids and citric acid) by using particular types of bacteria. In aerobic processes, the oxygen supply to the microorganisms is carried out by air blown into the fermenter. The excess air is released and forms foam. Aerobic processes are usually very foam-intensive, since the amount of escaping air is much larger compared to the amount of carbon dioxide in anaerobic processes.
FRESH YEAST
Antifoam agents for fresh yeast: Struktol® J 633, Struktol® J 673 A, Struktol® SB 2020 and Struktol® SB 304
Products for the yeast industry
Besides defoamers for fresh yeast Schill+Seilacher "Struktol" GmbH offers further auxiliaries for the yeast industry: Extrusion aids, emulsifiers and brightener for baker's yeast.
Extrusion aids
It is well known that sometimes it is difficult to put solid yeast into pounds as the line easily breaks. By Struktol extrusion aids the plastic properties of the yeast are improved so that even with a high dry matter content a smooth and flexible yeast strand is achieved and the speed of the extruder can be increased. The application of Struktol extrusion aids should be into the extruder or into the line press.
Advantages at the use of Struktol extrusion aids:
- will make the solid yeast smooth
- serve as a lubricant during packaging into pounds
- are odourless
- are tasteless
- speed up the pounding machine
Extrusion aids: Struktol® PF, Struktol® PF A and Struktol® SB 420
Emulsifiers
Struktol emulsifiers for fresh yeast form an emulsion with the extracellular water and an optical brightening of the yeast is obtained. By masking the extracellular water, the durability of the yeast is increased and early autolysis is prevented. In order to achieve a good distribution and to preclude a possible mottle of the yeast line it is recommendable to predilute the Struktol emulsifying agent with water in relation 1:1 up to 1:3 before application. The application of Struktol emulsifiers should be into the extruder or into the line press.
Advantages at the use of Struktol emulsifiers:
- will make the solid yeast smooth
- will brighten the yeast
- prevent quick drying of the yeast
- serve as a lubricant during packaging into pounds
- are odourless
- are tasteless
Emulsifiers: Struktol® J 600, Struktol® J 600 A and Struktol® SB 420