4微生物的营养与培养基解析.ppt

* * * * * 表示方法：Eh 或 rH2，单位为V（伏）或mV（毫伏） E’：pH=7.0时的某对氧化还原偶的氧化还原电势 各种微生物对培养基的氧化还原电势的要求： 好氧微生物：适宜的Eh=+0.3~+0.4V，在Eh0.1V以上的环境中均能生长 兼性厌氧微生物：+0.1V以上呼吸、+0.1V以下发酵 厌氧微生物：只能在+0.1V以下生长 培养基是多氧化还原偶的复杂电化学系统，测出的Eh值仅代表其综合结果。 对微生物影响最大的是：分子氧和分子氢的浓度 培养基中常用的还原剂：巯基乙酸、抗坏血酸、硫化氢、半胱氨酸、谷胱甘肽、二硫苏糖醇等。 * 4.经济节约 配制培养基时，应尽量考虑利用价廉并且易于获得的原料作为培养基的成分，特别是在工业发酵中，培养基用量很大，更应该考虑到这一点，以便降低产品成本。】 设计培养基时应考虑该培养基的应用目的，即： 是培养菌体还是积累代谢产物？ 是实验室种子培养还是大规模发酵？ 代谢产物是初级代谢产物还是次级代谢产物？ * * * * * * * * * Types of Culture Media Culture media may be classified into several categories depending on their composition or use. A chemically-defined (synthetic) medium (Table 4a and 4b) is one in which the exact chemical composition is known. A complex (undefined) medium (Table 5a and 5b) is one in which the exact chemical constitution of the medium is not known. Defined media are usually composed of pure biochemicals off the shelf; complex media usually contain complex materials of biological origin such as blood or milk or yeast extract or beef extract, the exact chemical composition of which is obviously undetermined. A defined medium is a minimal medium (Table4a) if it provides only the exact nutrients (including any growth factors) needed by the organism for growth. The use of defined minimal media requires the investigator to know the exact nutritional requirements of the organisms in question. Chemically-defined media are of value in studying the minimal nutritional requirements of microorganisms, for enrichment cultures, and for a wide variety of physiological studies. Complex media usually provide the full range of growth factors that may be required by an organism so they may be more handily used to cultivate unknown bacteria or bacteria whose nutritional requirement are complex (i.e., organisms that require a lot of growth factors). Most pathogenic bacteria of animals, which have adapted themselves to growth in animal