Common concentration methods for separating and purifying fermentation products
1. Evaporation concentration: Using heating to vaporize the water in the fermentation broth, thereby increasing the concentration of the product.
Advantages: Simple operation, relatively low equipment cost, suitable for concentration of various fermentation products, and can quickly and effectively increase product concentration.
Disadvantage: For some heat sensitive fermentation products, high temperature may cause denaturation and deactivation; Meanwhile, the evaporation process requires a significant amount of energy and incurs high costs. For example, evaporation concentration can be used to concentrate some amino acid fermentation broths that are not very sensitive to temperature, but caution should be exercised when using certain protein fermentation products.
2. Membrane separation and concentration: Ultrafiltration: Utilizing the sieving effect of ultrafiltration membranes, small molecules such as water and inorganic salts are allowed to pass through, while the fermentation products of large molecules are retained on one side of the membrane, thereby achieving concentration.
Advantages: It can be operated at room temperature with minimal impact on the activity of fermentation products; Can effectively remove impurities from the fermentation broth and improve the purity of the product; The operation process is simple and easy to automate control.
Disadvantages: The membrane has a high cost and is easily contaminated, requiring regular cleaning and maintenance; For some impurities with molecular weights similar to the target product, they may not be completely removed.
Nanofiltration: Its membrane pore size is between ultrafiltration membrane and reverse osmosis membrane. Under pressure, it allows some small molecules and monovalent ions to pass through, while having a high retention rate for divalent and higher ions and fermentation products with larger molecular weights, thus achieving concentration and separation.
Advantages: It has good concentration effect, can operate at lower pressure, and relatively low energy consumption; The impact on thermosensitive substances is relatively small, and the activity of the product can be maintained.
Disadvantages: The selectivity of nanofiltration membranes is relatively low, and some impurities may be trapped together with the target product; The lifespan of the membrane is limited and requires regular replacement.
3. Freeze concentration: Freeze the fermentation broth below freezing point to form ice crystals, and then separate the ice crystals from the concentrated solution through centrifugation, filtration, and other methods to achieve concentration.
Advantages: Suitable for the concentration of thermosensitive fermentation products, as operating at low temperatures can maximize the preservation of product activity; No other chemicals will be introduced, which has a minimal impact on the purity of the product.
Disadvantages: The operation process is relatively complex, requiring special refrigeration and separation equipment, and the cost is high; The concentration factor is relatively low and may require multiple operations to achieve the desired concentration.
4. Precipitation concentration: By adding a precipitant to precipitate the fermentation product or impurities, and then separating the precipitate, the concentration of the fermentation broth can be achieved. For example, for protein fermentation products, organic solvents, salts, and other precipitants can be added to precipitate the protein, and then the supernatant can be removed to achieve concentration.
Advantages: Simple operation and low cost; It can simultaneously achieve concentration and preliminary purification of the product.
Disadvantages: The selection of precipitant needs to be based on the properties of the fermentation product, otherwise it may affect the activity and purity of the product; The precipitation process may be affected by factors such as solution pH and temperature, and strict control is required.
5. Dialysis concentration: Using the dialysis effect of a semi permeable membrane, small molecules such as water and inorganic salts in the fermentation broth are dialyzed out, while the fermentation products of large molecules remain in the dialysis bag, thus achieving concentration.
Advantages: Simple operation, no need for special equipment; It can be operated at room temperature with minimal impact on the activity of the fermentation products.
Disadvantages: Slow concentration speed, requiring a longer time to reach the desired concentration; The cost of dialysis bags is high and they are prone to rupture, requiring careful handling.
