The application and development of membrane separation technology in the plant extraction industry

Membrane separation methods have their distinct characteristics. For example, it requires no heating, has low energy consumption, can operate at low temperatures, offers high separation efficiency, does not require the addition of chemical reagents, and does not damage heat-sensitive substances. It is very suitable for separating highly thermosensitive, volatile systems that react with chemical reagents. The advantages of membrane separation over traditional separation methods are obvious. 􀁺 Reduce the number of processing steps, shorten the production cycle, save raw materials (especially ethanol), lower costs, and contribute to safer production in the factory. Saving ethanol is a very typical example. The extract obtained from traditional Chinese medicines is often purified using the decoction-alcohol precipitation method: the decoction is concentrated to about 0.5–1.0 g (of crude drug)/mL, ethanol is added to raise the alcohol concentration to 60%–70%, and the precipitate is used to remove impurities. To extract 100 kg of medicinal materials, 100–200 L of the solution requiring alcohol precipitation is needed; to achieve an ethanol concentration of 60% in this solution, 1.7 times that volume of ethanol (95%) must be added, which amounts to 170–340 L of ethanol. 􀁺 It maintains the components of the original formula while increasing the content of the active ingredients, whether in the preparation of traditional Chinese medicine injections or in experiments to extract these active ingredients. 􀁺 It has an excellent effect in removing impurities, and can improve the clarity of injections and oral solutions. Tannins, starch, resins, and proteins present in traditional Chinese medicine extracts are difficult to remove using conventional water-alcohol methods. By employing ultrafiltration membranes with a specific retention value, these impurities can be removed, thereby improving the clarity of the extract. With long-term storage, even for up to one and a half years, its clarity remains unchanged. 􀁺 It has an excellent effect in removing pyrogens. Pyrogens are metabolic products of microorganisms; the use of appropriate ultrafiltration membranes can achieve pyrogen removal levels that meet pharmacopoeial requirements. 􀁺 It has an excellent sterilization effect. After ultrafiltration, a sterile and clear medicinal solution is obtained, replacing heat sterilization and preventing precipitation in some medicinal solutions due to heating. Some pigments can be removed. 3. Examples: The purification of stevioside using ultrafiltration showed that it has good decolorization capabilities and effective impurity removal, and can effectively address the precipitation problems that occur during production as well as the foaming issue during filling. Compare the effects of ultrafiltration and alcohol precipitation in extracting chlorogenic acid from honeysuckle. Using ultrafiltration, a recovery rate of 99% for chlorogenic acid can be achieved when the ultrafiltration volume is 1.5 times. When precipitated with 70% alcohol, the recovery rate of chlorogenic acid was only 67%. An experimental comparative study was conducted on psoralen injections prepared by the ultrafiltration method and the water-alcohol method. The results showed that the ultrafiltration process has a shorter duration (only 1–2 days, compared to 6 days for the water-alcohol method), results in less loss of active ingredients, and yields products with a darker color and better clarity. Thin-layer chromatography showed that the main active components, psoralen and isotopsoralen, contained in it were both higher than those obtained by the water-alcohol method.

It seems there are quite a lot of people working in plant extraction from time to time. If no one else would do it, I’ll do it myself. Hehe

I work in membrane separation, currently in the pharmaceutical industry. I haven’t been involved in plant extraction yet. If you are from the manufacturer side, we can carry out a pilot test for you if there is a need. Hehe.

Membrane separation is in itself a rather broad field; it comes down to knowing how to make good use of microfiltration, ultrafiltration, and nanofiltration technologies! Select the type of membrane based on the characteristics of different natural extract materials!