摘要
世界上由于癌症、耐药细菌、真菌等引发的疾病越来越多，尤其是艾滋病和器官移植导致的免疫系统能力下降，随之带来真菌感染机率的增加，使得人们对抗生素的需求也不断地增加。另外，随着抗生素的广泛使用，耐药性问题已经不可忽视，寻找新的抗生素是解决这一问题的方法之一。过去，抗生素大多来源于土壤微生物，近年来，植物内生菌因为其种类繁多、开发较少，而逐渐受到人们的关注。另外，不断有研究者发现，植物内生菌产生的抗菌物质不但种类繁多，而且有许多是未开发的新物质。因此，植物内生菌因具有作为新型药物来源的巨大潜力而备受关注。但现阶段对植物抗菌内生菌的研究刚刚开始，对其特性了解还不够深入而无法对其充分利用，因此，对植物抗菌内生菌的研究不仅能带来巨大的社会效益还具有现实的理论意义。本实验室从中华芦荟叶中分离到了一株具有广谱抗菌活性的内生细菌A11，并对该菌株及其活性物质进行了前期的研究，在前期研究的基础上，本试验对植物内生菌A11进行了发酵条件优化的研究，以求增加抗菌活性物质产量的同时减少发酵液的黏度，并对A11所产生的抗菌活性物质进行分离纯化技术的研究，为其后的物质结构鉴定打下基础，试验结果如下：
1．植物内生细菌A11抗菌活性物质发酵条件的优化
为了在增加植物内生细菌A11发酵活性物质产量的同时减少发酵液粘度，对植物内生细菌A11进行了装液量、接种量、初始pH值、最适碳源和氮源、甲醇添加剂以及表面活性剂等发酵条件的研究。结果表明：通过单因素试验得到增加活性物质产量并降低发酵粘度的最适碳源、氮源及其含量分别为蔗糖0.5％、硝酸铵0.25％，装液量30％，接种量5％，初始pH 7.0-8.0，28℃、200r／min发酵72h。发酵促进剂实验表明，甲醇既无法作为碳源被A11利用，也对A11产生活性物质无任何促进作用；而表面活性剂(Tween-80)则对活性物质的产生起到了抑制的作用。
2．抗菌活性物质的分离纯化
An increase in the number of people in the world having health problems caused by various cancers, drug-resistant bacteria, and fungi is a cause for alarm. Together with this is an increasing need for more and better antimycotics, especially as the human population is developing more fungal infections as a result of the AIDS epidemic and the increased numbers of patients with organ transplants, whose immune systems are weakened. Inaddition, as antimycotics has been wildly uesed, drug resistance become a problem which could not be ignored. And one of the way to solve this problem is to seach for novel antimycotics. In the past, most of the antimycotics came from edaphon. It now appears that an enormous, relatively untapped source of microbial diversity is represented by the microbial endophytes. They produce antimicrobial agents and seem to have unique genetic and biological systems that may have applications outside the host plant in which they normally reside. Endophytes has being given more attentions as they has a novel source of potentially useful medicinal compounds . Now we are just at the beginning of the researching on endophytes, we can not take full advantages of endophytes because many of their characters have not been understood, in that case, reseach on the anti-microbe endophytes not only brings vast social profits but also has realistic theoretic significance. An endophytic bacterium named All has been isolated from the foliage of Aloe chinenses(Haw.) Baker by our laboratory. All has wide-spectrum antibacterial activity and has been identified by physiological and biochemical techniques. Based on the prior reseach, this scientific dissertation was studied on finding out the optimum fermentation condition, which could be used to increase the production of active substances and reduce the emplastic
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