影響培養(yǎng)基滅菌效果的因素
發(fā)布時間：
2022-11-16
作者：
哪家公司去哪里購買好培養(yǎng)基
影響培養(yǎng)基滅菌效果的因素
培養(yǎng)基滅菌是否徹底，影響因素很多，除了培養(yǎng)基內(nèi)雜菌的種類和數(shù)量，滅菌溫度的高低，時間長短外，還取決于：
1. 營養(yǎng)成分的保持
濕熱滅菌時，微生物被殺死的同時，培養(yǎng)基的營養(yǎng)成分也遭到了一定的破壞，特別是氨基酸和維生素。如在121℃，僅20min，就有59%的賴氨酸和精氨酸及其他堿性氨基酸被破壞，蛋氨酸和色氨酸也有相當(dāng)數(shù)量被破壞。在熱的作用下某些營養(yǎng)成分還可能因受熱而相互之間發(fā)生反應(yīng)，造成培養(yǎng)基中原有營養(yǎng)成分的數(shù)量變化，因而影響培養(yǎng)基質(zhì)量。
2. 微生物的耐熱性
細菌芽孢的熱阻較大，滅菌所需要的時間取決于把細菌芽孢減少到所規(guī)定數(shù)目的時間。
3. pH值
pH值對微生物的耐熱性影響很大。pH值介于6.0~8.0時，微生物最不易死亡。pH<6.0時，微生物比較容易死亡，此時H+很容易滲入微生物的細胞，從而改變細胞的生理反應(yīng)，促使其死亡。所以培養(yǎng)基的pH越低，所需的時間也越短。
4. 培養(yǎng)基成分
油脂、糖類及蛋白質(zhì)等組成的高濃度有機物會包于細胞的周圍形式一層薄膜、影響熱的傳導(dǎo)。而高濃度的鹽類、色素則削弱其耐熱性，滅菌較易。例如：大腸桿菌在水中加熱至60-65℃便死亡，在10%糖液中需70℃加熱4-6分鐘才死亡，在30%糖液中需30分鐘才死亡。一般糖類含量較多的時候最好選用115℃，30分鐘；一般的培養(yǎng)基可選擇121℃20分鐘。
5. 泡沫
泡沫中的空氣形成隔熱層，使熱量難以滲透進去，殺死其中的雜菌。
6. 顆粒
顆粒小，容易滅菌，顆粒大，則難滅菌。對于含有少量較大顆粒及粗纖維的培養(yǎng)基，可用粗濾的方法（不應(yīng)影響培養(yǎng)基質(zhì)量）予以除去，培養(yǎng)基結(jié)塊會造成培養(yǎng)基滅菌的不徹底。
7. 滅菌鍋內(nèi)空氣是否排凈
這個是影響滅菌是溫度和壓力比例關(guān)系的要點，同樣達到了相同的壓力的情況下，如果空氣未能排凈，也就是說不是純蒸汽滅菌，此時的溫度不一定能達到目的要求，會嚴重影響滅菌效果。
（文章來源：食品實驗室服務(wù)）
Factors that influence the sterilization effect of culture medium.
The sterilization of the culture medium is thorough, and the factors affecting it are many. Besides the type and quantity of the bacteria in the medium, the degree of sterilization temperature and the length of time are also dependent on:
1. Retention of nutrients.
When the bacteria are killed, the nutrients in the medium are also destroyed, especially amino acids and vitamins. As in the 121 ℃, 20 min, there are 59% of lysine and arginine and other basic amino acid are destroyed, methionine and tryptophan are quite a number of damaged. Under the action of heat, certain nutrients may react with each other due to heat, resulting in a change in the number of original nutrients in the medium, thereby affecting the quality of the medium.
2. Heat resistance of microorganisms.
The thermal resistance of bacterial spores is large, and the time required for sterilization depends on the time required to reduce the bacterial spores to the specified number.
3. The pH
The pH value has great influence on the heat resistance of microorganisms. When the pH value is between 6.0 and 8.0, microorganism is the most difficult to die. When pH<6.0, microorganisms are relatively easy to die. At this point, H+ can easily infiltrate into the cells of microorganisms, thus changing the physiological response of the cells and causing them to die. So the lower the pH of the medium, the shorter the time.
4. Medium composition.
High concentrations of organic matter, such as fats, sugars and proteins, can be encapsulated in the surrounding form of the cell and affect the conduction of heat. The high concentration of salt and pigment weakens its heat resistance and is easy to sterilize. Such as e. coli in water heated to 60-65 ℃ was killed, in 10% sugar solution to 70 ℃ heat 4 to 6 minutes before death, in 30% sugar solution need 30 minutes before death. When had better choose a more sugar content in 115 ℃, 30 minutes; General medium can choose 121 ℃ for 20 minutes.
5. The bubble
The air in the bubble forms an insulating layer that makes it difficult to penetrate and kill the bacteria.
6. Particles
Small particles, easy to sterilize, large particles, difficult to sterilize. For medium containing a small amount of large particles and coarse fiber, the method of coarse filtration (which should not affect the quality of the medium) should be removed, and the culture medium should not be completely sterilized.
7. Whether the air in the sterilized pan is clean.
This is affecting the relationship between sterilization temperature and pressure ratio is, the main points of the same at the same pressure, if the air is not clean, that is not pure steam sterilization, the temperature can not achieve the goal, will seriously affect the sterilization effect.
(source: food laboratory services)