How to preserve Edible Fungi

I. the principle of strain preservation

There are many ways to preserve bacteria, but the principle is more or less the same. First of all, good purebred should be selected. Make use of spores, spores and nutrients of microorganisms; secondly, according to their physiology and biochemistry, artificially create conditions such as low temperature, dryness or hypoxia to inhibit the metabolism of microorganisms and reduce their life activities to a very low degree or in a dormant state, so as to prolong the life of the strain and keep the original characteristics of the strain, and prevent variation. No matter which preservation method is used, no death, no pollution of miscellaneous bacteria and no degradation are required in the process of strain preservation.

II. Methods of strain preservation

1. The method of periodic transplantation and preservation at low temperature. The bacteria to be preserved were inoculated on suitable slope culture medium and cultured at suitable temperature. when the mycelium grew all over the slope, the mycelium was taken out and stored in 3-5 ℃ low temperature dry place or 4 ℃ refrigerator and freezer. The bacteria were transferred and transferred every 4-6 months, which should be determined according to the characteristics of the bacteria. When preservation, we should pay attention to the ambient temperature should not be too high, to prevent mold through the cotton plug into the tube. Therefore, if the cotton plug is used, the cotton plug can be wrapped with clean sulfuric acid paper or Kraft paper, which can not only reduce the chance of pollution, but also prevent the culture medium from drying. Except volvariella volvacea, other edible fungi can be preserved by this method.

2. Liquid paraffin preservation method. Take the chemically pure liquid paraffin (no moisture, no mildew) in a triangle bottle, add cotton stopper and wrap paper, sterilize under the pressure of 1 kg / square centimeter for 1 hour, and then put it in a 40 ℃ thermostat for several days to evaporate the moisture until the paraffin oil is completely transparent. The treated paraffin oil was transferred to the blank slope and cultured at 28-30 ℃ for 2-3 days. It was proved that there was no miscellaneous bacteria growth before it could be used. Then the liquid paraffin is injected into the inclined tube to be preserved by aseptic operation. The amount of injection should be 1-1.5 cm higher than the slope of the culture medium, plug it with a rubber plug, seal it with solid paraffin, and store it upright in a low temperature and dry place. The preservation time is more than one year, and the preservation time can be extended at low temperature.

3. Sand pipe preservation method. Take the river sand and soak it in water for several times, remove the coarse particles through a 60-mesh sieve, soak it in 10% hydrochloric acid for 2-4 hours, remove the organic matter, rinse with water until the pH of the running water reaches neutral, dry and set aside. At the same time, soak the lean ridge soil or vegetable garden soil with water to make it neutral, precipitate, discard the supernatant, dry and grind it, sift it with a 100-mesh sieve, mix the treated sand and soil with (2-4): 1, suck out the iron with a magnet, then pack it into small test tubes or ampoules, pack it with cotton, wrap it with paper (1.5kg / square centimeter, 1 hour), and then sterilize it with dry heat (160kg / square centimeter, 1 hour). 2-3 hours) 1-2 times, aseptic test, qualified use. The bacteria that have formed spores are injected into 3-5 ml of aseptic water under aseptic conditions, scrape the moss to make bacterial suspension, and then drop the bacterial solution into the sand pipe with aseptic straw to soak through the sand. Put the inoculated sand pipe into a vacuum dryer filled with desiccant and connect it with a vacuum pump for several hours until the sand is dry. Vacuum drying should be completed within 48 hours after spore insertion to avoid spore germination. The prepared sand pipe is sealed with paraffin and can be preserved for 2-10 years at low temperature.

4. Filter paper preservation method. Take white (collect dark spores) or black (collect white spores) filter paper, cut into 4 × 0.8 cm paper strips, spread them in a petri dish and wrap them with paper for sterilization (1 kg / square cm, 30 minutes). The spores were collected by hook suspension method, and the spores fell on the filter paper. Put the filter paper strip containing spores into the preservation test tube, and then put the preservation test tube into the dryer for 1-2 days, remove the moisture of the filter paper, make the moisture content of the filter paper reach about 2%, and then store it at a low temperature. 5. Natural matrix preservation method

⑴ wheat grain preservation method: rinse the wheat without shrunken grains and impurities, soak for 12-15 hours, boil with water for 15 minutes, continue hot soaking for 15 minutes, make the wheat grains swell without breaking, drain and spread out to dry, so that the water content of the wheat grains is about 25%. Mix calcium carbonate and gypsum into cooked wheat grains (10 kg: 133 g: 33 g), mix evenly, put them into test tubes, each tube is about 2-3 grams, then clean the test tubes, plug cotton plugs, sterilize 1.5 (1.5 kg / square centimeters, 2 hours), set aside after aseptic inspection, inoculate the test tube matrix after cooling, culture at the right temperature, and coat the cotton plugs with paraffin after the mycelia grow full. Store at a low temperature. Transfer every two years or so.

⑵ bran koji preservation method. Take fresh wheat bran and sift through 60 mesh to remove coarse grains. Mix the bran and tap water at 1:1, put it in a small test tube, each tube is packed with a cotton stopper, wrap it with paper, sterilize it under high pressure (1.5kg / square centimeter, 30 minutes), and set aside after passing the sterility test. transfer the robust bacteria growing on the inclined medium to the aseptic bran koji tube, although the bran in the small test tube is in a loose state. Culture at the right temperature until the mycelium is full of bran, put the bran koji tubule in the dryer and store at low temperature or at the right temperature.

6. Normal saline preservation method. Take 0.7-0.9 grams of pure sodium chloride, put it into 100% ml of distilled water, stir and pack test tubes evenly, 5-10 ml per tube, sterilize (1 kg / square centimeter, 30 minutes). After passing the sterility test, the bacteria to be preserved were put into the potato glucose liquid medium and cultured at the right temperature for 5-7 days. In aseptic operation, a few cultured bacteria are injected into a qualified normal saline test tube, stuffed with aseptic rubber plugs, coated with paraffin and preserved at room temperature or low temperature.

7. Freeze vacuum drying. The cultured and abundant bacteria or spores were suspended in sterilized serum, egg white and skim milk to make bacterial suspension. the suspension was packed in sterilized glass ampoules with aseptic operation, each tube was about 0.3-0.5ml, and then connected with the freeze-drying device with a pressure rubber tube. The ampoules were placed in a freezing tank for rapid freezing at-30 ℃ to-40 ℃, and emptied and dried in the frozen state. The ampoules were melted and sealed in vacuum and stored at 20 ℃. Generally, the ampoules could be preserved for more than ten years, but the cost was high.

8. Liquid nitrogen cryopreservation. First of all, the bacteria to be preserved are prepared into bacterial suspensions; secondly, ampoules are prepared, 0.8 ml cryoprotectant 10% (volume ratio) glycerin distilled water solution is added to each bottle, and cotton plugs are sterilized (1 kg / square centimeter, 5 minutes). After aseptic inspection, access to the bacteria to be preserved, fuse the mouth of the bottle to check whether there is air leakage, put the sealed ampule bottle in the freezer and slowly cool it at a rate of 1 ℃ per minute, so that the collection is gradually and evenly frozen until-35 ℃. After that, the freezing speed does not need to be controlled. After the ampoule is frozen, it is immediately put into a liquid nitrogen tank and stored at-150 to-196 ℃.